A NATIONWIDE STUDY OF FREEWAY MERGING OPERATIONS

By

Johann H. Buhr Research Assistant

Donald R. Drew Head of Design and Traffic Department

Joseph A. Wattleworth Assistant Research Engineer

and

Thomas G. Williams Research Assistant

Texas Transportation Institute Texas A&M University College Station, Texas

Sponsored By U.S. Bureau of Public Roads Contract No. CPR-11- 2842

For Presentation at the Annual Meeting of the Highway Research Board

Washington, D. C. January 16-20, 1967

A NATIONWIDE STUDY OF FREEWAY MERGING OPERATIONS

ABSTRACT

This paper introduces the research project entitled "Gap Accep­tance and Traffic Interaction in the Freeway Merging Process" which forms a part of a four-year program on freeway merging undertaken by the Bureau of Public Roads.

Field studies for the collection of data were performed on a na­tionwide basis at a number of selected entrance ramps, utilizing an aerial photographic technique. This technique, the data reduction methods and the study sites selected are described in detail.

Data editing routines and the analysis of the data for basic traffic parameters are discussed and some of these parameters used to illustrate the merging operation at each study site. The qualitative effect of various geometric elements on the operation as mirrored by the traffic parameters of volume, density, speed and acceleration noise are discussed.

This paper further serves to demonstrate not only the nature of the data available, but also the vast quantity of data involved.

The op1n1ons, findings, and conclusions expressed in this publication are those of the authors and not necessarily those of the Bureau of Public Roads.

INTRODUCTION

The engineer's problem in freeway design is basically one of esti­mating the parameters defining the traffic demand, capacity, and level of service of the facility. However, as a chain is only as strong as its weakest link, so the over-all level of service on a freeway is highly subject to the operation in critical sections, manifest by either sudden increases in traffic demand or the creation of intervehicular conflicts within the traffic stream, or a combination of both. Such regions of more restrictive vehicular operation often occur in the vicinity of en­trance ramps. It is therefore imperative that these regions be con­sidered when determining the design volume and capacity of a facility. A knowledge of the operational characteristics and traffic requirements at such locations is essential for proper planning, design and control.

To this end the Texas Transportation Institute was awarded a re­search contract entitled "Gap Acceptance and Traffic Interaction in the Freeway Merging Process," by the U.S. Department of Commerce, Bureau of Public Roads. This research problem forms part of the program of Traffic Systems research undertaken by the Bureau.

Scope of the Project

Generally, the objective of this project is the development of de­tailed criteria on traffic stream interaction and geometric features pertaining to the freeway merging process, so as to develop methods for increasing capacity and safety through effective control and functional design.

While primary emphasis is on gap acceptance characteristics, the system under study includes the freeway from a point upstream to a point downstream of the entrance ramp proper and takes due regard of other traffic characteristics, geometric features, and .environmental conditions.

The ultimate purpose of the research is the application of this in­formation in traffic design and operation and in computer simulation.

Field studies for the gathering of data used in the testing and eval­uation of existing and developed criteria, were carried out at a large number of selected entrance ramps ranging over the length and breadth of the continental United States.

1

The study had to be completed in the relatively short time of eighteen months with the result that close attention had to be paid to proper scheduling of the many activities involved in order to attain the wide-ranging objectives. Figure 1 shows the critical path scheduling envisioned at the start of the project.

Objectives of this Paper

The objectives of this project are so varied in scope and compre­hensive in nature as to prohibit its being covered in its entirety in this report. The main purpose of this paper is to report on the data collec­tion and reduction techniques employed, to describe the ramps under study and to indicate the nature of the data available for purposes of future reference. Furthermore, the authors wish to report on the editing and preliminary analysis of the data to present a comprehensive summary of merging operation at 32 ramp-freeway connections special­ly chosen to include diverse geometric, geographic, environmental and operating conditions.

DATA COLLECTION

The data collection phase of this study was carried out at thirty­two entrance ramps located in eight of the major metropolitan areas in six states. Data were collected on a continuous basis at each ramp, to provide the researchers with information on all the variables that could possibly influence the merging maneuver. The many variables involved clearly necessitated the need for a permanent record of the operation, making continual back reference feasible. Perhaps the best such permanent record is provided by photographic techniques and the de­cision to use time-lapse photography was therefore almost a foregone conclusion. Furthermore, the need for collecting data at many differ­ent locations, in different parts of the country, made the use of one or more stationary cameras impractical. The data collection procedure had to be independent of the availability of vantage points such as con­veniently located tall buildings or overhead structures, and had to be extremely mobile, requiring little equipment and few personnel. Since the studies were to be carried out in areas under the jurisdiction of various highway authorities another requirement of the procedure was that it should interfere as little as possible with the day to day opera­tion of the organization concerned. All these considerations led to the development of an aerial photographic technique for the continuous

2

JULY '65

AUG.

SEPT.

OCT.

NOV.

DEC.

JAN.

FEB.

MAR.

APR.

MAY

JUNE

JULY

AUG.

SEPT.

OCT.

NOV.

DEC.

JAN. '67

WRITE FLIGHT CONTRACT 8o SPECS

BIBLIOGRAPHY

----- 19 BIDS 8o CONTRACT APPROVAL

FLIGHT

DEVELOP FILM

CPM NETWORK DIAGRAM FOR RAMP MERGING RESEARCH PROJECT

Figure 1

3

THEORY

CHARACTERISTICS

SIMULATION

Ill

study of a length of highway.

Aerial Technique and Equipment

The flight pattern consisted of orbiting the study area in a circu­lar or elliptical pattern with a light airplane, while training the camera on the center of the study area, usually the nose of the entrance ramp. The aircraft used was a Cessna 206 with the baggage door of the rear passenger compartment modified to accept a large, clear plexiglass window. The left rear seat was removed to permit mounting of the camera inside the aircraft. This allowed filming through the plexi­glas s window without any noticeable glare or distortion. Figure 2 shows the modification, which has proven quite satisfactory, and Figure 3 shows the camera mounted inside the aircraft.

The camera used was a 35 millimeter Automax G- 2 data record­ing camera, fitted with Automax Model 250 control head and an Automax 25 intervalometer which could pulse the camera at the rate of 1/2, 1, 3, 5, or 10 pictures per second and with a setting for cine operation at 16 frames per second. Power was supplied to the camera by two 12 volt D. C. batteries, connected in series to provide sufficient voltage to drive the camera, which maintained a constant speed through a voltage range of 18 to 36 volts D. C. The camera has interchangeable lenses, is adaptable to a 400 foot or a 1000 foot film magazine and has a variable shutter speed ranging from 1/ 64th to 1/1 OOOth of a second. The camera also has a data chamber containing a clock with a sweep second hand, a frame counter and a data slate, all of which is projected as an image on each frame of the film being taken.

The camera was mounted inside the aircraft on a small tripod fitted with a Miller fluid head. The tripod was mounted on special rub­ber "shoes 11 to dampen vibrations and secured to the floor of the air­craft with adaptable wires fitted with turnbuckles. To further dampen vibrations, a piece of medium density rubber was installed between the fluid head and the top of the tripod.

Experimentation with lenses of different focal lengths used at dif­ferent flight altitudes led to the development of the chart shown on Figure 4 which was used throughout the study to avoid conflict with other air traffic. It was found that when a distance on the freeway of greater than 1800 feet was covered, the film analysis became extreme­ly cumbersome as it was difficult to follow a single vehicle through the study area under conditions of high traffic density. This difficulty was due to shadows, vehicle image size and general lack of definition,

4

AIRCRAFT DOOR MODIFICATION

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caused mainly by atmospheric haze.

In the data collection on this project, three 400 feet magazines were used, while filming was done at a rate of five frames per second. This allowed three filming periods of approximately 22 minutes each. Fig­ure 5 shows a sequence of four photographs taken from a film, showing the study area from different positions in the orbit.

Both color and black and white film was used in some of the initial studies, but it was soon found that at twice the price, color film had little if any advantage over black and white. Kodak Plus-X Panchro­matic Type 4231 film having a speed rating of ASA 80 was mostly used but on overcast days or on days when light readings were low, such as during the peak hours in the winter months, a somewhat faster film, Kodak Double-X Panchromatic Type 5222, having a speed rating of ASA 250 was used. The slower speed film is finer grained than the high speed film and was therefore preferred whenever light conditions permitted its use.

The filters used to reduce the veiling effect of atmospheric haze present at all times to a greater or lesser degree, were Wratten fil­ters no. 8 (K- 2), no. 15 (G) or no. 23 (A) depending upon the degree of air pollution.

Exposure settings were obtained using a Weston Master V Univer­sal Exposure Meter model 748. It was found desirable to obtain light readings on the ground before filming since exposure settings deter­mined at altitudes above 1000 feet could differ as much as 3 f- stops from that determined at ground level on days of extreme haze condi­tions, resulting in overexposure of the film. The best image definition was obtained by filming just after a frontal passage or following a rain shower when there is little atmospheric haze.

After the initial teething troubles, this filming technique proved extremely satisfactory. A crew of two, consisting of pilot and camera­man, could take off in the morning, fly several hundred miles, film a location or two and return to home base with minimum disturbance to the local authorities and negligible preparational furor. This mobility, plus the substantially reduced cost involved originally led to the choice of a light airplane over a helicopter. One problem encountered in the circling technique was that of changing light conditions when the sun is close to the horizon or when the study area is located close to a large body of water. This could lead to the film being overexposed when the camera is in a certain phase of the orbit and then underexposed when it is on the opposite side. This problem could, however, be overcome

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with a camera equipped with an "electric eye" that automatically ad­justs the aperture, or with a camera which allows this adjustment to be made during filming. Interference with other air traffic did not pre­sent much of a problem mainly through the cooperation of the person­nel of the Federal Aviation Agency Air Traffic Control Center in each area filmed. Information regarding approach and departure routes of aircraft and safe altitudes for filming was provided by the local air traffic controller. The fine service rendered by the local radar and control tower personnel permitted the filming of study sites in such high density air traffic areas as Los Angeles' International, San Fran­cisco's International, New York's Kennedy and La Guardia, Chicago's O'Hare and Houston's International. As an additional safety precaution, it was sometimes deemed desirable to have a third person in the air­plane as an observer to keep a sharp lookout for other aircraft.

Ground Control Stations

As ground control stations for referencing the position of vehicles as they traverse the study area, marks were made on the shoulder of the freeway and the ramp. Experimentation with various marking materials and mark designs led to the use of 3M Lane Marking Tape in

. an alt~:r:nating pattern of arrowhead shaped and parallel line marks as .shown on Figure 6. The marking tape is a white nonreflective six inch­es wide tape with a bituminous adhesive on one side, making its appli­cation and removal extremely easy and convenient. The marking tape is first placed in position as shown on Figure 7 and is then cemented by rolling it down with a special roller applicator, as shown on Figure 8. Upon completion of the study, the tape can easily be removed by simply peeling it from the pavement. It was found that for improved visibility from high altitudes, the most important dimension of the reference mark was its length rather than its width or shape.

Normally, reference marks were placed at 200 feet intervals radiating from the concrete nose of the ramp. However, on short ramps of 400 feet or less, marks were placed at 100 feet intervals.

STUDY LOCATIONS

The study locations were selected to meet several operational and geometric requirements. Operational cons ide rations required the s e­lection of study sites operating at or near capacity while unaffected by

9

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TYPICAL STUDY SECTION

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NOTE: ALL STRIPES ARE WHITE NON-REFLECTIVE LANE MARKING TAPE

PLACING OF MARKER TAPE Figure 7

TAPE BEING ROLLED DOWN

Figure 8

11

upstream or downstream conditions, so that a pure merging situation existed. Local authorities were extremely helpful in suggesting study sites and providing volume data to aid in the final selection of sites. Before any filming was done at a location, the operation there was field checked to determine the approximate volumes and to evaluate the ef­fect of any downstream restrictions. Based on the traffic operations during the time of the field observation, the study period was selected so that free flow merging operation prevailed and so that the merging volume was near capacity. In spite of this careful checking of the study sites, the operation during the film studies was not always the same as during the field checks due to changes in traffic patterns, accidents, or some other temporary situation, with the result that the operational requirements were not always successfully met.

Geometric considerations in the selection of study sites required the coverage of a wide range of geometries in the ramps to be studied. Variations in acceleration lane length, angle of convergence and ramp grade were sought, primarily at locations where the freeway alignment was straight and fairly level. The considerable range of geometries covered among the ramps selected can be seen on Figure 9 which illu­strates the variation in acceleration lane lengths and angles of con­vergence of the ramps studied.

The coverage of these two geometric elements is perhaps better illustrated by Table 1 which shows the number of ramps studied that fall into each group of acceleration lane lengths and angles of entry.

TABLE 1

NUMBER OF RAMPS STUDIED IN EACH CELL OF ACCELERATION LANE LENGTH AND ANGLE OF ENTRY

Angle of Acceleration Lane Length Entry 0-400 400-600 600-800 above 800

0-4 1 2 3 3 4-8 l 4 3 4

above 8 4 2 4 0

The range of ramp shapes studied is illustrated in Figures 10 through 13 showing the geometric characteristics of a ramp with a long

12

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X NEW YORK AREA \] CALIFORNIA

0 I 0 CHICAGO, ST. LOUIS 14-l 0 0 HOUSTON

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LENGTH OF ACCELERATION LANE IN FEET

Figure 9

acceleration lane and a small angle of entry (Figure 10); a ramp with a long acceleration lane and a large angle of entry (Figure 11), a ramp with a short acceleration lane and a small angle of entry (Figure 12) and a ramp with a short acceleration lane and a large angle of entry, (Figure 13).

After extensive correspondence with highway officials in many parts of the country and reviewing a multitude of plans and profiles, ramps were selected for study in California, in Los Angeles, Sacra­mento, and the San Francisco Area, in the New York Metropolitan Area, in Detroit, Michigan, in Chicago, Illinois, in St. Louis, Missouri and in Houston, Texas.

TABLE II

STUDY LOCATIONS IN CALIFORNIA

Location of Ramp

San Francisco Area

Milbrae, southbound on Bayshore Freeway Broadway, southbound on Bayshore Freeway Lakeshore, southbound on MacArthur Freeway Ashby, southbound on Eastshore Freeway Monument Junction, southbound on I 680

Sacramento

Watt Avenue, southbound on I 80

Los Angeles

Number of films

1 2 1 2 2

2

Coldwater Canyon, westbound on Ventura Freeway 2

Experimental studies were first carried out in Houston, Texas, mainly for the purpose of checking out the equipment and techniques and developing the various procedures to be followed into a smoothly­running organization. The first out- of- state study was done in California in November of 1965, where the ramps listed in Table II

14

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RAMP FREEWAY

-1.0% NO~E

1 ~

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PROFILE

GEOMETRIC CHARACTERISTICS DATA LENGTH OF ACCELERATION LANE 1200 FEET SHAPE OF ACCELERATION LANE r--- PARALLEL ANGLE OF CONVERGENCE AT RAMP NOSE

--10

ANGLE OF CONVERGENCE 2-FT.- OFF PAVEMENT EDGE 10 c---RAM-P GRADE AT NOSE - -1.0%

------~-

~FfE-EWAY GRADE AT NOSE -1.0% NUMBER OF FREEWAY LANES 3 !----·-------·--------------·-NUMBER OF RAMP LANES I

1-----·-··-··-------------·---·---~-----------·-.

TANGENT FREEWAY CURVATURE RAMP CURVATUFfE _____________________ SLIGHT RIGHT

1-- -CURB6FFSET AT NOSE - - --------- ---2 FEET !---------------·------·---·----

600 FEET LENGTH OF RAMP

GEOMETRIC CHARACTERISTICS JERICHO (RT. 25) EASTBOUND ENTRANCE RAMP

LONG ISLAND EXPRESSWAY, NEW YORK

Figure 10

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RAMP FREEWAY

-------- -

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PROFILE

GEOMETRIC CHARACTERISTICS DATA LENGTH OF ACCELERATION LANE 1120 FEET SHAPE OF ACCELERATION LANE TAPER ANGLE OF CONVERGENCE AT RAMP NOSE 7°30' ANGLE OF CONVERGENCE 2FT. OFF PAVEMENT EDGE 20 RAMP GRADE AT NOSE LEVEL FREEWAY GRADE AT NOSE LEVEL NUMBER OF FREEWAY LANES 4 NUMBER OF RAMP LANES I FREEWAY CURVATURE TANGENT RAMP CURVATURE TANGENT CURB OFFSET AT NOSE 10 FEET LENGTH OF RAMP 500 FEET

GEOMETRIC CHARACTERISTICS ASHBY AVENUE SOUTHBOUND ENTRANCE RAMP

EASTSHORE FREEWAY, SAN FRANCISCO

Figure II

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-0.51% NOkE ~ PROFILE FREEWAY

GEOMETRIC CHARACTERISTICS DATA LENGTH OF ACCELERATION LANE 435 FEET SHAPE OF ACCELERATION LANE TAPER ANGLE OF CONVERGENCE AT RAMP NOSE 20 ANGLE OF CONVERGENCE 2FT. OFF PAVEMENT EDGE 20

-RAMP GRADE AT NOSE -0.51% -------·--FREEWAY GRADE AT NOSE -0.51% NUMBER OF FREEWAY CANES 3 f---------------------------

I ~!J.M~~B___QF RAMf'_l,~~£:,L ____________ FREEWAY CURVATURE TANGENT RAMP CURVATURE TANGENT

··----CURB OFFSET AT-NOSE 2 FEET

~ENGTHOF RAMP ____ 380 FEET

GEOMETRIC CHARACTERISTICS ROCKAWAY NORTHBOUND ENTRANCE RAMP

VAN WYCK EXPRESSWAY, NEW YORK

Figure 12

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----- )~~----~~~~ RAMP No!sE FREEWAY

PROFILE

GEOMETRIC CHARACTERISTICS DATA LENGTH OF ACCELERATION LANE 335 FEET SHAPE OF ACCELERATION LANE TAPER ANGLE OF CONVERGENCE AT RAMP NOSE 14° ANGLE OF CONVERGENCE 2FT. OFF PAVEMENT EDGE 14° RAMP GRADE AT NOSE LEVEL FREEWAY GRADE AT NOSE LEVEL NUMBER OF FREEWAY LANES 3

~~MBER OF RAMP LANES I FREEWAY CURVATURE TANGENT RAMP CURVATURE TANGENT CURB OFFSET AT NOSE 2 FEET

_LENGTH_OF RAMP 225 FEET

GEOMETRIC CHARACTERISTICS BROAD STREET SOUTHBOUND ENTRANCE RAMP

GULF FREEWAY, HOUSTON

Figure 13

were filmed. The table also shows the number of films taken at each location. The study locations are listed according to the metropolitan area in which they are located, rather than by the exact suburb. Draw­ings of these study locations, with a table giving the major geometric characteristics, are shown in Figure 11 and Figures 14 through 19.

After the California study, it became clear that the study tech­niques and equipment had to be re-evaluated. Some of the films taken at the locations listed and all of the films taken at some other loca­tions were not useable. This re-evaluation led to several improve­ments. In the first place, the camera, which until this time had a fixed shutter speed, was modified to have adjustable speeds as des­cribed earlier. Secondly, the camera mounting was slightly altered so as to further dampen the effect of vibrations. Thirdly, the use of dif­ferent kinds of film and different filters were investigated and finally, the flight pattern was altered. Until this time circles were made at a radius of approximately half-a-mile. It was found desirable however that the circle be pulled tighter so that the films be taken from more directly above the traffic. Circling at a quarter of a mile radius pro­vided a better view of the study area, facilitating the analysis, and yet was wide enough that the pilot and plane could maintain the circle for long periods of time.

During this time, studies were carried out in Houston and the tech­niques and procedures perfected. The Houston studies were carried out at the eight ramps listed in Table III.

These ramps are illustrated on Figure 13 and Figures 20 through 25 also indicating the major geometric characteristics.

In May of 1966, the second out-of- state study was made to New York, Detroit and Chicago. This trip was a great success except for being marred by unfavorable weather, making a third trip, this time to Chicago and St. Louis necessary. The ramps filmed on these trips are listed in Table IV.

Drawings of most of these ramps, with tables listing the major geometric characteristics appear as Figures 10 and 12 and Figures 26 through 38.

19

N 0

RAMP FREEWAY

--- ---

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_... - - - ----No!SE

PROFILE

GEOMETRIC CHARACTERISTICS DATA LENGTH OF ACCELERATION LANE 675 FEET SHAPE OF ACCELERATION LANE TAPER ANGLE OF CONVERGENCE AT RAMP NOSE 30

ANGLE OF CONVERGENCE 2FT. OFF PAVEMENT EDGE 20

RAMP GRADE AT NOSE LEVEL FREEWAY GRADE AT NOSE LEVEL NUMBER OF FREEWAY LANES 4 NUMBER OF RAMP LANES I FREEWAY CURVATUR.E TANGENT RAMP CURVATURE TANGENT CURB OFFSET AT NOSE 10 FEET LENGTH OF RAMP 350 FEET

GEOMETRIC CHARACTERISTICS MILBRAE AVENUE SOUTHBOUND ENTRANCE RAMP

BAYSHORE FREEWAY, SAN FRANCISCO

Figure 14

N ........

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.RAMP I FREEWAY

PROFILE

GEOMETRIC CHARACTERISTICS DATA f-------;LENGTH__Q[ ACCELERAJIOf\1 L,A]'JE ______ 1025 __!'!:~::..:T ____ ---1

SHAPE OF ACCELERATION LANE TAPER ANGLE OFCONVERGENCE-ATRAMP-NOSE___ 7-Y. DEGREES

-ANGLE0FcC>N-vERGE:r·.fcE:2FT:-oi=F'F>AvEMENT EDGE ---2-oE:GRE:E:s:c==~-----j RAMP GRADE AT NOSE - SUGHT DOWNGRADE --FREEWAY GRADE XT-Nosf_______________ LEVEL - -----NUMBEROFFREEWAYLANES ------- 4

--NUMBER Cii=" RAMP LANES ___ ----- ---------- --~---

-F'REEWAY CURVATURE- ------ - --TANGE,;i;-- -------RAMP-CLJRVATURE- - -------- -- -- - -- sCIGHTR-IG-HT- -----

ctTRB OFFSET AT NOSE- - . -- - -- - IOFEET -LENGTH OF RAMP --- - ·--- - -- - - ---- ---3oo--FEEf+ ________ _

GEOMETRIC CHARACTERISTICS BAYSHORE FREEWAY, BROADWAY ENTRANCE RAMP

SAN FRANCISCO, CALIFORNIA

Figure 15

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PROFILE

GEOMETRIC CHARACTERISTICS DATA LENGTH OF ACCELERATION LANE~--- 700 FEET SHAPE OF ACCELERATION -i.:AN_E _______ TAPER

---ANGLE OF CONVERGENCE AT RAMPN~- 5" ANGLE OF CONVERGEN_f_E~_E:T. OFFPAVEMENT EDGE 2" RAMP GRADE +I.O'J. .. ·----~--··------ -~

FREEWAY GRADE +4.0'1. NUMBER OF FREEWAY LANES----= =-====------= 4 --NUMBER OF RAMP LANES j----1 ----------FREEWAY CURVATURE

·---~--- --- ··-------------TANGENT

·------·--------~-··

RAMP CURVATURE _ TANGENT _ ~-----CURB OFFSET AT NOSE --- ------------ - __ 10 FEET LENGTH OF RAMP -~-------- -- --·--- ----

450 FEET -- -~

GEOMETRIC CHARACTERISTICS LAKESHORE SOUTHBOUND ENTRANCE RAMP

MACARTHUR FREEWAY, LOS ANGELES

FIGURE 16

N LV

--N-

~% NOSE +0.40%

FREEWAY PROFILE

GEOMETRIC CHARACTERISTICS DATA LENGTH OF ACCELERATION LANE 600 FEET SHAPE OF ACCELERATTON-LANE___________ TAPER -

--A~·fGLE OF CON-VERGENCE AT-RAf•iFq;josE______ 4° ~~~-

ANGLE OF CONVERGENCE 2FT. OF-F-PAVEMENT EDGE --4° - -RAMPGRADE- AT-NOSE---------------------=-=-=-t-~-o+-=o-.4:c:%::--~~~-

------------ - --------------1 FREEWAY GRADE AT NOSE +0.4% NUMBER-OF-FREEWAY LANES -2~~--~

-NU-MBER OF RAMP LANE-S~----~-~·-- ---·-·------- _______ T ______________ _

--FREE¥vAYfUR\fA_f@~E_ -__:_=_::--=-___:-=====-~ __-:-_::_~~J§HT~LEEL _ -------1

--~i~~~T~~~~i~:NOSE - ----- ---- ~ i- -!t}~FiE~§Jil"_ -· -----

GEOMETRIC CHARACTERISTICS MONUMENT JUNCTION SOUTHBOUND ENTRANCE RAMP

I-680 IN PLEASANT HILL (SAN FRANCISCO)

Figure 17

N ,j::..

I N

I

I RAMP

NOISE -0.28°/o ~AY 0.12%

PROFILE

GEOMETRIC CHARACTERISTICS DATA LENGTH OF ACCELERATION LANE 690 FEET SHAPE OF ACCELERATION LANE PARALLEL ANGLE OF CONVERGENCE AT RAMP NOSE 40

---~··-

ANGLE OF CONVERGENCE 2FT. OFF PAVEMENT EDGE 40 RAMP GRADE AT NOSE -0.3% FREEWAY GRADE AT NOSE -0.12% NUMBER OF FREEWAY LANES 2 NUMBER OF RAMP LANES I FREEWAY CURVATURE SLIGHT RIGHT RAMP CURVATURE SLIGHT RIGHT CURB OFFSET AT NOSE 2 FEET LENGTH OF RAMP 500 FEET

GEOMETRIC CHARACTERISTICS WATT AVENUE SOUTHBOUND ENTRANCE RAMP

I-80, SACRAMENTO

Figure 18

··--

N \Jl

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------------I --=-==-- -

I NO.SE -1.0% FREEWAY

PROFILE

GEOMETRIC CHARACTERISTICS DATA LENGTH OF ACCELERATION LANE 970 FEET SHAPE OF ACCELERATION LANE PARALLEL ANGLE OF CONVERGENCE AT RAMP NOSE so ANGLE OF CONVERGENCE 2FT. OFF PAVEMENT EDGE so

·--------RAMP GRADE AT NOSE -0.8% FREEWAY GRADE AT NOSE -1.0% NUMBER OF FREEWAY LANES 3 NUMBER OF RAMP LANES I FREEWAY CURVATURE TANGENT RAMP CURVATURE TANGENT CURB OFFSET AT NOSE 2 FEET LENGTH OF RAMP SOO FEET

GEOMETRIC CHARACTERISTICS COLDWATER CANYON AVENUE WESTBOUND ENTRANCE RAMP

VENTURA FREEWAY, LOS ANGELES

Figure 19

-0.7S% RAMP

N 0'

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PROFILE

GEOMETRIC CHARACTERISTICS DATA LENGTH OF ACCELERATION LANE 610 FEET SHAPE OF ACCELERATION LANE PARALLEL ANGLE OF CONVERGENCE AT RAMP NOSE 12" 15 ANGLE OF CONVERGENCE 2FT. OFF PAVEMENT EDGE 12" 15 RAMP GRADE AT NOSE LEVEL FREEWAY GRADE AT NOSE -0.40% NUMBER OF FREEWAY LANES 4 NUMBER OF RAMP LANES I FREEWAY CURVATURE TANGENT RAMP CURVATURE TANGENT CURB OFFSET AT NOSE 2 FEET LENGTH OF RAMP 103 FEET

GEOMETRIC CHARACTERISTICS WESLAYAN EASTBOUND ENTRANCE RAMP

SOUTHWEST FREEWAY, HOUSTON

Figure 20

N -J

L .J ~ I

-- - - - - c: - - - - - -- - - - - - - - - - -- --- - - -- - - - - - -- - -- - - - -- ---- - - - - - - - - - - ----

- - - - -- - - - - -- - - - - - - - - - -- - - - - - - - - -- -- - - - - - - - - - - - - - - --- - - - - - - - -- - -- - - -

~ NO~E RAMP AND FREEWAY

PROFILE

GEOMETRIC CHARACTERISTICS DATA LENGTH OF ACCELERATION LANE 620 FEET

-- ---------------- SHAPE OF ACCELERATION LANE --------- _?ARALLE:h _______ _ _ f\I'JQb_E_ OF CONVER_G~NCE_ 1\T RAfv1P NQ_SE _A~G_LE QF 90_NVEJ'lG_E_NCE~_FT. _ OFF_fi\VEMENT EDGE

RAMP GRADE AT NOSE -~EEWAY GRADE-ATNOSE --- .. ------- ----- --- -------~-- ..

NUMBER OF FREEWAY LANES -------- ··- -- ------------ - --- . -- ---------

NUMBER OF RAMP LANES --FREEWAY cuRvA-TuRE ___ _

-----·--------- ---- ----

- _flMI_P___gJ_B¥_ATl)_RE _____ _ CURB OFFSET AT NOSE

------cENGTH OF RA~fp-

12° 12° LEVEL LEVEL 4 I

GEOMETRIC CHARACTERISTICS BUFFALO SPEEDWAY WESTBOUND ENTRANCE RAMP

SOUTHWEST FREEWAY, HOUSTON

Figure 21

- -- - -- -

- - -- --- =--

N 00

---~

r

\N '\

~ ~ I

--- ---~--:::::==- -=._.-- -_..:;:--- ---------- ---- - --- -~--

- - ~ -=

~

FR££W

~ I RAMP + NO,SE +0.3%

PROFILE

GEOMETRIC CHARACTERISTICS DATA LENGTH OF ACCELERATION LANE 340 FEET SHAPE OF ACCELERATION LANE TAPER ANGLE OF CONVERGENCE AT RAMP NOSE 100 ANGLE OF CONVERGENCE 2FT. OFF PAVEMENT EDGE 100 RAMP GRADE AT NOSE +0.3% FREEWAY GRADE AT NOSE -0.3% NUMBER OF FREEWAY LANES 3 NUMBER OF RAMP LANES I FREEWAY CURVATURE TANGENT RAMP CURVATURE TANGENT CURB OFFSET AT NOSE 2 FEET LENGTH OF RAMP ISO FEET I

GEOMETRIC CHARACTERISTICS CULLEN EASTBOUND ENTRANCE RAMP

GULF FREEWAY, HOUSTON

Figure 22

N ~

\ \

- ~ j[l +-=

[============~~~~-~;-;;;;;;;;;;~~;;~;;;;;;;;~~~~~~~~~~~~~~~~~~~~~~: -- -~ -- -::=:::-

r-------------, ( ~ ( ~~ J) "~~

RAMP +0.5% N01

SE +?.."'"'

FREEWAY

PROFILE

GEOMETRIC CHARACTERISTICS DATA

f----¥.NGI_I::!_.QF ACC~.[,~f'l_E-IIQN LANE _ ~Q__f_EET ~):!APE OF ACCELERATION LANE TAPER ANGLE OF CONVERGE-NCEAT-RAMP-NO~-- -· _?" _________ -----

--

----ANGi..:EOFCONVERGENCE 2FYOFF PAVEMENT-- i-.----··-RAMP GRADTAT NOSE_____ ---·--------- ·-+0.5%----··-F':f~~~.Y{AY G.B_~D~ AI:NOSE -~~-~~~- --+0.5% _____ ------ .

NUMBER OF FREEWAY LANE 3 NUMBER OF RAMP LANES - ~-------

FREEWAY CURVATURE -----~-. -_----- Tti,N~NT. _ ___ ----1 ~~R~A=MP CURVATURE TA~N~G~E~N~T _____ ~ LcuRB-..QJ'"f~ET AT NO~E ---==~~======~- =-~Fgr___ ____ _

LENGTH OF RAMP 170 FEET

GEOMETRIC CHARACTERISTICS DUMBLE EASTBOUND ENTRANCE RAMP

GULF FREEWAY, HOUSTON

Figure 23

w 0

\-.N '\..

I ' ~@~ - ~~~~==--~ 1 .J- - --------- ~~::::~~--~------ _-_-_-_-_-_-_-_-__ -_- __ -_-__ -_-_-_-_-__ -_-_--- -_-_-_-_-_-_-_- -~- _-_-_-_ ~ -_ --~ ~-=-= -_-~--- _-_-_-_--~

~~~-~ =~~-~ ~-_- ~ _-:_ -_ -__ -_---__ -_-_-_- . -- ==-----[7 duul!ffl 1 ~

V/1/f/!/f/ I r------------- (

F~~SE 0.5% RAMP

PROFILE

GEOMETRIC CHARACTERISTICS DATA LENGTH OF ACCELERATION LANE 680 FEET SHAPE OF ACCELERATION LANE PARALLEL ANGLE OF CONVERGENCE AT RAMP NOSE 10° ANGLE OF CONVERGENCE 2FT. OFF PAVEMENT EDGE 10° RAMP GRADE AT NOSE -0.5% FREEWAY GRADE AT NOSE -0.5% NUMBER OF FREEWAY LANES 3 NUMBER OF RAMP LANES I FREEWAY CURVATURE TANGENT RAMP CURVATURE TANGENT CURB OFFSET AT NOSE 2 FEET LENGTH OF RAMP 380 FEET

GEOMETRIC CHARACTERISTICS WAYSIDE EASTBOUND ENTRANCE RAMP

GULF FREEWAY, HOUSTON

Figure 24

·-·-

w .......

' N

( \ ====-------' l ~ -+;:::::::--- ~

-

·---- ----

\S - ~~ FREEWAY +0.2%

PROFILE

GEOMETRIC CHARACTERISTICS DATA f-----cL-:=Ec:-:N-=cGT=H:-:-::0-=F-:A:-::-CCELER AT ION LANE 310 FEET

SHAPE OF ACCELERATION LANE ____ TAPER ANGLE OF CONVERGENCE AT RAMP NOSE 10•

I NOSE

I

ANGL~_Qf CONVfRGE:N-CEZFT. OFF f_AVEME.!'I_!_ EDGE 10• -----~ RAMP GRADE +0.3% FREEWAY GRADE +0.2,~~~· _____ _

~_!J_MBER OF F'REEWAYj::ANE:s-_:- ==-=::::::_~~-------f--"'-3·~-~--------NUMBER OF RAMP LANES I FREEWAY CURVATURE - TANGEN._.T _____ ~ RAMP CURVATURE TANGENT CURB OFFSET AT NOSE 2 FEET LENGTH OF RAMP 150 FEET

GEOMETRIC CHARACTERISTICS MOSSROSE NORTHBOUND ENTRANCE RAMP

GULF FREEWAY, HOUSTON

FIGURE 25

RAMP +0.3%

lJ.)

N

\N \

ii~t.:0Ii.t - - - ~~~----=----

RAMP

NqSE o 2..&__%. ____ _ --PROFILE

GEOMETRIC CHARACTERISTICS DATA LENGTH OF ACCELERATION LANE 700 FEET SHAPE OF ACCELERATION LANE PARALLEL

c-----ANGLE OF CO-NVERGENCE. AT RAMP NOSE 3" - ANGLE-OF. CONVERGENCE 2FT.OFF PAVEMENT EDGE 3"

r--------:::-.-·-----------~---- -----··-- ---2.0% RAMP GRADE AT NOSE r-----::-"-- - -----·- ---~-----

-2.0% ,___('"f~EEWAY G~~!_ -~"fJ'l_()_S_E_~--___ Nljt,l_§_ER OF FREEYV_AY LANES ______ 3

NUMBER OF RAMP LANES I ------------------ ----- ----------·

FREEWAY CURVATURE SLIGHT LEFT

=--RAMP CURV/HU~( ~·-----------=~~~==---=== SLIGHT LEFT CURB OFFSET AT NOSE 2 FEET LENGTH OF RAMP -- - ·------- 660 FEET

GEOMETRIC CHARACTERISTICS COMMUNITY DRIVE EASTBOUND ENTRANCE RAMP

LONG ISLAND EXPRESSWAY, NEW YORK

Figure 26

-

w w

-N~

----~-=--

--~--- -_-_-_-_-_-_-_-_------ -

-- _-_----------- -_-_-__ -_-_-_-_-_-_-_------

RAMP

-5.0%

~ FREEWAY

GEOMETRIC

No'sE +0.79%

CHARACTERISTICS DATA LENGTH OF ACCELERATION LANE 1200 FEET SHAPE OF ACCELERATION LANE PARALLEL ANGLE OF CONVERGENCE AT RAMP NOSE 10

~_NGLE OF CONVERGENCE 2FT. OFF PAVEMENT EDGE 10 RAMP GRADE AT NOSE +0.79% FREEWAY GRADE AT NOSE --f-- +0.79% NUMBER OF FREEWAY LANES 3

- NUMBER OF RAMP LANES - I ~REEWAY CURVATURE ______ -------r---- SLIGHT LEFT

__ RAMP-~l)l'l_'{!>.TURf:_ ~-= ~- ______________ __ SLIGHT LEFT CURB OFFSET AT NOSE 2 FEET

' LENGTH OF FfAMP- ----------- 1200 FEET

GEOMETRIC CHARACTERISTICS

PROFILE

LONG ISLAND EXPRESSWAY WESTBOUND ENTRANCE RAMP TO CROSS ISLAND EXPRESSWAY, NEW YORK

Figure 27

I.N ~

\ \

r-­--:;;=-.~a::-;;:S-C::;;:W;-:-;~=~=~~ 0~ ~::-~ .. ~:,::::,~::;-:=,=~ :2~~~~:~===:;;.;;:-m;;;;:;-:-;;-;:;;-:;~-------;-.;; ·~'l')'.-$,•;,J~.:'HJ'. -~~'-'~- "' ''"'"'-~·""'~·"'"'1/•b'::t.'.01t.·:\:\'.t.l~'·"-'

f-- - - - - - - - --- - - - - - - - -- -- - -- - ~-- - - - - - - - - - - - - - ~ - - - - - - - - - -~--

-~

RAMP

FREEWAY

... ,. ·0%

NdsE +0.25%

PROFILE

GEOMETRIC CHARACTERISTICS DATA LENGTH OF ACCELERATION LANE 500 FEET SHAPE OF ACCELERATION LANE PARALLEL ANGLE OF CONVERGENCE AT RAMP NOSE 50 ANGLE OF CONVERGENCE 2FT. OFF PAVEMENT EDGE 50

RAMP GRADE AT NOSE +0.25% FREEWAY GRADE AT NOSE +0.25% NUMBER OF FREEWAY LANES 3 NUMBER OF RAMP LANES I FREEWAY CURVATURE TANGENT RAMP CURVATURE TANGENT CURB OFFSET AT NOSE 12 FEET LENGTH OF RAMP 520 FEET

GEOMETRIC CHARACTERISTICS 69TH ROAD SOUTHBOUND ENTRANCE RAMP

GRAND CENTRAL EXPRESSWAY, NEW YORK

Figure 28

w Ul

~j - - _-_ .. - I -- ~--- ---- -- ·~ ~·. : -- _-_-

t--_--=--__ - __ -_---_---

l 1 l r l r RAMP

~NOISE -0.4%

PROFILE

GEOMETRIC CHARACTERISTICS DATA LENGTH OF ACCELERATION LANE 693 FEET SHAPE OF ACCELERATION LANE TAPER ANGLE OF CONVERGENCE AT RAMP NOSE s• 15'

~~GLE OF CONVERGENCE 2FT. OFF PAVEMENT EDGE s• 15' RAMP GRADE -0.3%

r---FREEWAY GRADE. -0.4% I---NUMBER OF FREEWAY LANES 3

NUMBER OF RAMP LANES I FREEWAY CURVATURE TANGENT

,----RAMP CURVATURE TANGENT c----f..URB OFF~~T AT .NOSE 2 FEET L___ LENGTH OF RAMP 450 FEET

GEOMETRIC CHARACTERISTICS CHENE EASTBOUND ENTRANCE RAMP EDSEL FORD EXPRESSWAY, DETROIT

FIGURE 29

---=---_____,..-

w 0"-

-

FREEW.G;

- -- -

l~ Jl JL - - -- - -

- -

-- - ~ ~

NOISE +0.4%

GEOMETRIC CHARACTERISTICS DATA LENGTH OF ACCELERATION LANE 500 FEET SHAPE OF ACCELERATION LANE TAPER ANGLE OF CONVERGENCE AT RAMP NOSE 7°15' ANGLE OF CONVERGENCE 2FT. OFF PAVEMENT EDGE 7°15'

~AMP-GRADE AT NOSE +0.4% r---FRE-EwAY GRADE AT NOSE-~--- +0.4%

NUMBER OF FREEWAY LANES 3 ------r--~MBER OF RAMP- LANES I f----FREEWAY-CURVATlfRE ________ TANGENT f---------'RAMP CURVATURE TANGENT r-- CURB OFFSETATNOSE-- 2 FEET ~ENGTHOF RAMP=-- _ _

-600 FEET

GEOMETRIC CHARACTERISTICS GRATIOT EASTBOUND ENTRANCE RAMP

EDSEL FORD EXPRESSWAY, DETROIT

FIGURE 30

I

j

w -J

r----

F----I""""'""

-

l

-

N---

~ --,. ' II.,'IH '

I~ I

'

c

NdsE -0.36% 0.36% RAMP AND FREEWAY

PROFILE

GEOMETRIC CHARACTERISTICS DATA LENGTH OF ACCELERATION LANE 660 FEET SHAPE OF ACCELERATION LANE TAPER ANGLE OF CONVERGENCE AT RAMP NOSE 3"30' ANGLE OF CONVERGENCE 2FT. OFF PAVEMENT EDGE 3"30' RAMP GRADE -0.36% FREEWAY GRADE -0.36% NUMBER OF FREEWAY LANES 3 NUMBER OF RAMP LANES I FREEWAY CURVATURE TANGENT RAMP CURVATURE TANGENT CURB OFFSET AT NOSE 2 FEET LENGTH OF RAMP 50 FEET

GEOMETRIC CHARACTERISTICS WARREN EASTBOUND ENTRANCE RAMP

SOUTHFIELD EXPRESSWAY, DETROIT

FIGURE 31

-

' - ---

~

w CXl

-

L '' ~N- ~------:= - ''·· -_-_-_ - -~

r------------------------ -------------~ --------------------------------- -----=...-

l r -· · 1 r -- ~ r -~ l r

+0.5% PROFILE

GEOMETRIC CHARACTERISTICS DATA LENGTH OF ACCELERATION LANE 515 FEET SHAPE OF ACCELERATION LANE PARALLEL ANGLE OF CONVERGENCE AT RAMP NOSE 4° 45 ANGLE OF CONVERGENCE 2FT OFF PAVEMENT EDGE 4°45' RAMP GRADE AT NOSE +0.5% FREEWAY GRADE AT NOS!:: +0.5% NUMBER OF FREEWAY LANES 3 NUMBER OF RAMP LANES I FREEWAY CURVATURE TANGENT RAMP CURVATURE TANGENT CURB OFFSET AT NOSE 2 FEET LENGTH OF RAMP 550 FEET

GEOMETRIC CHARACTERISTICS LINWOOD NORTHBOUND ENTRANCE RAMP

JOHN LODGE EXPRESSWAY, DETROIT

FIGURE 32

RAMP

No!s~y

l.V -.!)

~-- ----I---

~ ~ -

=

-- --- ------------

MEDIAN

PROFILE

GEOMETRIC CHARACTERISTICS DATA LENGTH OF ACCELERATION LANE 738 FEET SHAPE OF ACCELERATION LANE TA-PER ANGLE OF CONVERGENCE AT RAMP NOSE 6"

~NGLE OF CONVE-RGENCE 2FT. OFF PAVEMENT EDGE 6" c-----RAMP GRADE AT NOSE -0.42% r--- FREEWAY GRADE AT-NO·Sy--- -0.42% r---NUMBER OF FREEWAY LANES 4

NUMB-ER OF RAMP LANES I ~REEWAY CURVATURE - TANGENT r-----RAMP CURVATURE -- TANG_!oNT -~-CURBOFFSET-AT Nose-~--------- 2 FEET r--------- ------------ --- ---. - ------------------

432 FEET LENGTH OF RAMP

GEOMETRIC CHARACTERISTICS INDEPENDENCE AVENUE WESTBOUND ENTRANCE RAMP

EISENHOWER EXPRESSWAY, CHICAGO

Figure 33

0.42% NdsE RAMP -­FREEWAY

,j:>. 0

~ MEDIAN

-----------------------

f------ ---------- -----------ES==- - - - I

I RAMP NO,SE + 1.0%

FREEWAY PROFILE

GEOMETRIC CHARACTERISTICS DATA LENGTH OF ACCELERATION LANE 712 FEET SHAPE OF ACCELERATION LANE TAPER ANGLE OF CONVERGENCE AT RAMP NOSE so

~NGLE OF CONVERGENCE 2 FT. OFF PAVEMENT EDGE so RAMP GRADE AT NOSE +1.0% FREEWAY GRADE AT NOSE +1.0% NUMBER OF FREEWAY LANES 4 NUMBER OF RAMP LANES I FREEWAY CURVATURE SLIGHT RIGHT RAMP CURVATURE 1--- SLIGHT RIGHT

f--- CURB OFFSET AT NOSE 2 FEET LENGTH OF RAMP 350 FEET

GEOMETRIC CHARACTERISTICS KOSTNER AVENUE EASTBOUND ENTRANCE RAMP

EISENHOWER EXPRESSWAY, CHICAGO

Figure 34

RAMP AND No!sE FREEWAY

>+:-._.

-N__,........

MEDIAN

---------------------------

PROFILE

GEOMETRIC CHARACTERISTICS DATA LENGTH OF ACCELERATION LANE 785 FEET SHAPE OF ACCELERATION LANE PARALLEL ANGLE OF CONVERGENCE AT RAMP NOSE II" ANGLE OF CONVERGEf'fCE 2FT. OFF PAVEMENT EDGE II" RAMP GRADE ATNOSE. _ _!.~VE.1 ______ ··---FREEWAY GRADE AT NOSE -~ _\:._E_VEL ___

---NlTMBER6F.FREEWAYLANES ---~--~-NuMsE:in:in'~AMPTANEs-- -- I ----- F@EV[AY~~Ql'iSfl\IO:~~~----====~=--=- ___ = -··-- --------- ·-·------

____ .JAN(>ENT_ __________ RAMP CURVATURE SLIGHT RIGHT F -CURBOFFSETATNOSE ----- . --- --· ----- -·---

2 FEET ·-·-LENGTH-OFRA~-----·-·-- 925 FEET

GEOMETRIC CHARACTERISTICS DEMPSTER AVENUE NORTHBOUND ENTRANCE RAMP

EDENS EXPRESSWAY, CHICAGO

Figure 35

H:>. N

........----N-

I - - - - -~ ----------- --1--E:::--~----- --~--- --------

1-- -- - - - - - - - - - - -. - - - - - - - - - - - - - - - - - - - - - - - - - - - - - ~- -

PROFILE

GEOMETRIC CHARACTERISTICS DATA LENGTH OF ACCELERATION LANE 468 FEET SHAPE OF ACCELERATION LANE PARALLEL --ANGLE OF CONVERGENCE AT RAMP NOSE II" ANGLE OF CONVERGENCE 2FT. OFF PAVEMENT EDGE II" RAMP GRADE AT NOSE +0.49'1 FREEWAY GRADE ATNOSE ---- LEVEL NUMBER OF FREEWAY LANES 3 NUMBER OF RAMP LANES I FREEWtiYCURVATlTRE- ~ ----~- -- -- --==-~ -- t-- TANGENT RAMP CURVATURE 1-- SLIGHT RIGHT

1------CUR_B()Ff':SETAT !'10_§~- ~--- ____ --- -- ·----- 2 FEET LENGTH OF RAMP 1020 FEET

- -- -

GEOMETRIC CHARACTERISTICS PETERSON AVENUE NORTHBOUND ENTRANCE RAMP

EDENS EXPRESSWAY, CHICAGO

Figure 36

NObE FREEWAY

~

~ w

RAMP 1

~NO,SE FREEWAY

I N

I

-0.80%

PROFILE

GEOMETRIC CHARACTERISTICS LENGTH OF ACCELERATION LANE SHAPE OF ACCELERATION LANE ANGLE OF CONVERGENCE AT RAMP NOSE ANGLE OF CONVERGENCE 2FT. OFF PAVEMENT EDGE RAMP GRADE AT NOSE FREEWAY GRADE AT NOSE NUMBER OF FREEWAY LANES NUMBER OF RAMP LANES FREEWAY CURVATURE RAMP CURVATURE CURB OFFSET AT NOSE LENGTH OF RAMP

DATA 1500 FEET TAPER 2" IY2• -0.80% -0.80% 3 I TANGENT TANGENT 10 FEET 900 FEET

GEOMETRIC CHARACTERISTICS PULASKI ROAD EASTBOUND ENTRANCE RAMP

SOUTHWEST EXPRESSWAY, CHICAGO

Figure 37

.)::.

.)::.

~ N \

----------

+0.43%

PROFILE

GEOMETRIC CHARACTERISTICS DATA LENGTH OF ACCELERATION LANE 593 FEET SHAPE OF ACCELERATION LANE PARALLEL ANGLE OF CONVERGENCE AT RAMP NOSE 14Y." ANGLE OF CONVERGENCE 2 FT. OFF PAVEMENT EDGE 14Y." RAMP GRADE AT NOSE +0.43% FREEWAY GRADE AT NOSE

~~~-

_+0.43% NUMBER OF FREEWAY LANES 2 NUMBER OF RAMP LANES I FREEWAY CURVATURE TANGENT RAMP CURVATURE SLIGHT RIGHT CURB OFFSET AT NOSE 2 FEET LENGTH OF RAMP 600 FEET

GEOMETRIC CHARACTERISTICS BRENTWOOD AVENUE WESTBOUND ENTRANCE RAMP

DANIEL BOONE EXPRESSWAY, ST. LOUIS

Figure 38

+0.43% -----.:t~ FREEWAY

~4/ifp

TABLE III

STUDY LOCATIONS IN HOUSTON, TEXAS

Location of Ramp

Weslayan, eastbound on Southwest Freeway Buffalo Speedway, westbound on Southwest

Freeway Cullen, eastbound on Gulf Freeway Dumble, eastbound on Gulf Freeway Telephone, eastbound on Gulf Freeway Wayside, eastbound on Gulf Freeway Broad Street, eastbound on Gulf Freeway Mossrose, westbound on Gulf Freeway

TABLE IV

Number of films

4

2 3 5 3 4 4 2

STUDY LOCATIONS IN NEW YORK, DETROIT, CHICAGO AND ST. LOUIS

Location of Ramp

New York Area

Number of films

Jericho, eastbound on Long Island Expressway 2 Community Drive, eastbound on Long Island Expressway 3 Long Island Expwy., northbound on Cross Island Expwy. 3 Broadway, eastbound on Northern State Pkwy. 2 Brush Hollow Road, eastbound on Northern State Pkwy. 2 69th Rd. , Southbound on Grand Central Pkwy. 2 Rockaway, northbound on VanWyck Expressway 2

Detroit

Chene, eastbound on Edsel Ford Expressway Gratiot, eastbound on Edsel Ford Expressway Warren Ave., southbound on Southfield Expressway Linwood, northbound on John Lodge Expressway

45

2 2 2 2

TABLE IV - continued

Location of Ramp

Chicago

Independence Ave., westbound on Eisenhower Expwy. Kastner, westbound on Eisenhower Expressway Dempster Street, northbound on Edens Expressway Peterson, northbound on Edens Expressway Pulaski, eastbound on Southwest Expressway

St. Louis

Brentwood, westbound to Daniel Boone Expressway

DATA REDUCTION

Number of films

2 2 3 3 3

3

Before the data collection could be started, serious consideration had to be given the film analysis techniques and equipment to be used. The analist of time-lapse photographs has the choice as to time orien­tation or space orientation i.e. either measuring the time required for a certain fixed displacement or measuring the displacement over a certain fixed time interval. Either method has certain advantages and disadvantages over the other. Time oriented analysis requires a high-er rate of filming than space oriented analysis for the same accuracy, but is usually considerably faster to perform. Specialized projectors with automatic X- Y coordinate readout equipment are available for space oriented data reduction and these were considered for use on this project. However, because of the continuously changing space scale inherent in the technique of data collection used, space oriented analysis was rejected in favor of time orientation. To this end, marks were made along the freeway and the ramp at fixed intervals both up­stream and downstream of the ramp nose as described earlier. Time orientation as used on this project, has the further advantage of elimi­nating the need for maintaining a strict altitude or flight pattern during filming. The data reduction was performed on three 35 mm. projectors, two of which were Richardson Model 300 projectors as shown on Figure 39 and the third was a Vanguard projector, consisting of a Model M- 35CD

46

FILM ANALYSIS IN PROGRESS

Figure 39

47

projection head and a Model M- 13 projection case.

Data reduction consisted of following each vehicle on the outside freeway lane and each vehicle on the ramp through the study area, recording the frame number at which the vehicle crossed each reference mark. In this manner data was collected on the time - space trajectory of approximately sixty thousand vehicles. Further information taken off the films were the frame number at which each ramp vehicle entered the freeway and frame numbers at fixed time intervals so as to determine, and keep a running check on the rate of filming or camera speed. The vehicles were also classified into trucks and pas­senger cars. At the peak of the data reduction, for a period of about two months, nine analysis crews were working three eight-hour shifts per day. These data were then punched into computer cards for further processing by an electronic computer.

This gave rise to a library of traffic data on entrance ramp opera­tion of such magnitude and scope as has been heretofore unavailable.

DATA ANALYSIS

The vast amount of data collected on this project could only be processed by electronic computer and to this end, use was made of the facilities of the Texas A&M University Data Processing Center of which the principal computer is an IBM 7094.

In order to extract the most possible information with the highest possible sample sizes from the data, extreme care had to be taken with data editing routines for removing all possible errors made during the film analysis and punching of the data cards.

Error Routines

One such error detecting program simply scans the data for such obvious·errors as negative speeds, vehicle paths crossing or two ve­hicles at the same point at the same time. The latter seems to have been the most frequent mistake, caused by improper identification of vehicles from one picture to the next. This could easily happen under conditions of high density on the study section where, at the same time, the film image definition was less than ideal. The first editing pro­gram was written to detect these errors which could then easily be

48

rectified by going back to the original film.

Due to the circling technique of filming, certain problems were experienced in the data analysis that must be immediately evident to a practical person; the problem of missing data points. This could occur in several ways. For example, the reference mark at either end of the study section could be momentarily out of the viewfinder of the camera because of a sudden movement of the airplane. Sometimes even the whole study section could momentarily disappear from view. Normally this would cause a drastic reduction in the sample size of continuous study and in the length of the study section. These prob­lems were overcome by the second editing program. This program makes use of a digital incremental plotter to plot a time - space dia­gram of the operation on the study section during the study period. A sample from such a time - space plot is shown on Figure 40.

The blue lines on the diagram represent vehicle paths in time and space on the freeway and the red lines represent vehicles on the ramp. The red line of a ramp vehicle changes to blue at the first marked station after it enters the freeway.

The time - space traces begin where vehicles enter the study sec­tion, either at the beginning of the section or when a vehicle weaves into the outside freeway lane from the second lane. Similarly, traces terminate when a vehicle leaves the study area either at the end or by weaving into the second lane from the outside lane. A red line that terminates without changing to blue, indicates that a ramp vehicle entered the freeway and then changed lanes before it reached the next reference mark.

The uses of the time - space diagram are many and varied. In the first place, it was used for detecting errors in the data that could not be found by the first error routine. Such errors are usually evi­denced by sudden increases or decreases in speed (sharp changes in the slope of the time - space line) or by two lines coming very close together at certain points without actually crossing. (If it did cross, it would have been found by the first error program.) These probable errors were revealed by the time - space diagram and could then be checked by referring back to the film.

A second use of the time - space diagram was in simulating miss­ing data points. These missing data points were usually at the ends of the study section as explained earlier. As the computer cannot recog­nize the difference between a missing data point and a weaving vehicle, it was essential that these points be filled in. This was easily achieved

49

0 0

m

0 0

[[J

(J7

:z:Cl Do ~.

f-.-1 a: t­(JI

:z: >-<0

0

t.ur,j (J7 0 :z :;;:: Oo a:o LL ci 4-+-1 I II 1/ I ii-i

w U"l (_) 0 :z a:

t-D c.r;C: >-<"" o'

0

~VIII Ill 1uu; /II 1111111 1111 II Ifill II 1 Iff( II 1111 I 11 1111 I I b.OO 20.00 40.00 60.00 80.00 100.00 120.00 140.00 160.00 180.00

TIME IN SECONDS

TIME - SPRCE DIRGRRM BROADWRY NORTHBOUND ENTRANCE RAMP

BAYSHORE FREEWAY. SRN FRANCISCO

Figure 40

VEHICLE or-; RAMP VEHICLE ~N FREfNRY

by extrapolating the time - space path, taking due regard of the pre­ceding and following vehicle. It was felt that this technique introduced only negligible error and was to be preferred to either shortening the study section by at least 400 feet or to breaking the continuous study period up into a number of shorter intervals.

The digital plotter plots to an accuracy of 0. 01 inches, that is, an accuracy of 1 I 10 of a second on the time scale used. Although this accuracy is adequate for taking most measurements directly off the time - space plot, it was not used in this capacity. It did, however, further prove its use in revealing the general operating conditions on the study section at a glance and was also found to be an almost indis­pens able aid in the the writing and debugging of further programs.

Basic Traffic Parameters

Several programs were written to extract a number of basic traffic parameters from the data. One of these programs computes the speed -volume - density relationships of the traffic stream in three different ways; based on individual vehicles, based on one-minute averages. These relationships can be computed over any or all 100 feet or 200 feet intervals in the study section. Some typical examples of the com­puter output on the microscopic relationships, that is, based on in­dividual vehicles are shown in tables V, VI, and VII for the 200 feet section ranging from a distance of 400 feet to a distance of 200 feet up­stream of the nose. These tables not only display the basic traffic parameters measured during the study period, but also present fre­quency tables of each parameter for different levels of any of the other parameters in a fashion appropriate for the further analysis of the stochastic properties of the inter- relationships between speed, volume and density. For example, table Vis a two-way frequency table, the columns showing the distribution of gaps (volumes) for different speed levels and the rows showing the distribution of speeds for different levels of gap sizes (volume levels). Similarly, table VI displays speed

·-and space headway (density) distributions of volumes against densities. It should be noted that volumes are calculated by inverting gaps and densities by inverting space headways. Note the emergence of the volume- density curve in table VII.

51

TABLE V

MONUMENT JUNCTION SOUTHBOUND ENTRANCE RAMP ON 1680 PLEASANT HILL, SAN FRANCISCO

FREQUENCY TABLE OF GAPS AND SPEEDS STATION -4 TO -2

Speeds 0-25 25-35 35-40 40-45 45-50 50-55 55-60 60-65 65-75 75-99 Totals

Gaps 0- 1 0 2 1 8 3 2 4 1 0 0 21 1- 2 0 0 13 18 41 17 6 4 2 0 101 2- 3 0 5 7 20 25 14 5 2 1 1 80

\J1 N 3- 4 0 0 5 8 23 10 4 3 2 3 58

4- 5 0 1 3 5 8 5 6 5 1 0 34 5- 6 0 0 2 4 12 6 10 5 3 0 42 6- 7 0 0 1 5 10 3 4 4 0 2 29 7- 8 0 0 0 4 13 5 4 2 0 0 28 8- 9 0 0 1 2 7 1 5 1 0 1 18 9-10 0 0 1 0 5 1 1 3 1 0 12

10-11 0 0 1 3 0 2 2 1 1 0 10 11-12 0 0 {) 1 4 1 2 1 0 0 9 12-13 0 0 0 0 2 1 0 4 1 0 8 13-14 0 0 1 0 1 1 1 2 0 0 6 14-15 0 0 0 1 1 1 1 0 0 0 4

15-99 0 0 0 1 7 0 1 3 0 0 12

TOTALS 0 8 36 80 162 70 56 41 12 7 472

TABLE VI

MONUMENT JUNCTION SOUTHBOUND ENTRANCE RAMP ON 1680, PLEASANT HILL, SAN FRANCISCO

FREQUENCY TABLE OF SPACE HEADWA YS AND SPEEDS STATION -4 TO -2

Speeds 0-25 25-35 35-40 40-45 45-50 50-55 55-60 60-65 65-75 75-99 Totals

Space Headway

0- 40 0 0 0 0 0 0 0 0 0 0 0 40- 60 0 2 2 6 2 0 0 0 0 0 12

1.}1

60- 80 0 0 3 4 7 2 2 0 0 0 18 lN

80-100 0 0 6 12 7 3 3 4 0 0 35 100-120 0 2 3 4 12 l 2 0 0 0 24 120-140 0 2 3 13 13 3 0 l l 0 36 140-160 0 l 3 3 10 10 3 0 l 0 31 160-180 0 0 2 4 9 2 0 0 0 0 17 180-200 0 0 2 3 5 7 l l 0 0 19 200-240 0 l 4 3 16 7 4 0 l 0 36 240-280 0 0 l 4 10 6 0 l 0 0 22 280-320 0 0 2 4 5 2 3 l 0 l 18

320-360 0 0 l 2 6 2 2 2 l 0 16

360-400 0 0 0 3 6 3 4 l l 0 18

400-440 0 0 0 4 6 4 5 4 0 2 25 440-500 0 0 l 3 ll 3 5 2 l l 27

500-560 0 0 l 2 13 3 3 4 3 0 29 560-620 0 0 l l 2 4 3 3 0 0 14

620-999 0 0 l 5 22 8 16 17 3 3 75

TOTALS 0 8 36 80 162 70 56 41 12 7 472

TABLE VII

MONUMENT JUNCTION SOUTHBOUND ENTRANCE RAMP ON 1680, PLEASANT HILL, SAN FRANCISCO

FREQUENCY TABLE OF VOLUMES AND DENSITIES STATION -4 TO -2

Volume 0-10 10-20 20-25 25-30 30-35 35-40 40-45 45-50 50-55 55-60 60-99 Totals

Density 0- 10 101 4 0 0 0 0 0 0 0 0 0 105

10- 20 35 88 1 0 0 0 0 0 0 0 0 124 20- 30 0 41 26 5 0 0 0 0 0 0 0 72

U"1 30- 40 0 1 15 23 17 3 2 0 0 0 0 61 ,.j:.

40- 50 0 0 1 9 13 12 5 1 0 0 0 41 50- 60 0 0 0 0 6 8 6 1 3 4 1 29 60- 70 0 0 0 0 0 0 6 0 4 3 2 15 70- 80 0 0 0 0 0 0 0 0 4 2 4 10 80- 90 0 0 0 0 0 0 0 0 0 0 3 3 90-100 0 0 0 0 0 0 0 0 0 1 6 7

100-110 0 0 0 0 0 0 0 0 0 0 0 0 110-120 0 0 0 0 0 0 0 0 0 0 3 3 120-130 0 0 0 0 0 0 0 0 0 0 2 2 130-140 0 0 0 0 0 0 0 0 0 0 0 0

140-999 0 0 .o 0 0 0 0 0 0 0 0 0

TOTALS 136 134 43 37 36 23 19 2 11 10 21 472

Further output of this program consists of one minute and five minute ave rages of volume counts, one and five minute space and time mean speeds and one and five minute average densities calculated firstly as the inverse of the mean space headway, secondly as the mean of the inverse space headways and thirdly as defined by Lighthill and Whitham; the total travel time over the section divided by the product of the length of the study section and the time intervals used in averag­ing. As stated earlier, the program can compute this information for any or all of the sections in the study area, giving rise to output far too bulky for inclusion in this report.

Other programs used to extract basic traffic parameters describing the merging operation, include programs to investigate ramp vehicle speeds and accelerations, freeway gap distributions over shorter time intervals and ramp arrival distributions. Another program investigates the averages of a number of traffic parameters measured over short time intervals at each consecutive space interval. These parameters include: (1) volume, (2) density, (3) speed, (4) energy, (5) shock wave speeds, (6) speed noise, (7) accelerations, (8) acceleration noise, (9) expected length of queue, and (10) probability of a gap less than the critical gap. The program further proceeds to plot contour maps of each of these variables using a digital incremental plotter, thus effec­tively demonstrating their variation in both time and space. For the purpose of illustrating the merging operation in this report, only five of these contour maps were selected and drawn up on a figure. One such figure was prepared for each film taken, illustrating the merging operation during that period. Figure 41 is such a figure displaying the parameters of volume, speed, density, acceleration noise and prob­ability of a gap of greater than three seconds on a continuous basis in both time and space. This figure was derived from one of the films taken at the Dempster Street northbound entrance ramp on Edens Ex­pressway, illustrated earlier in figure 35. The figures are read in exactly the same manner as a conventional contour level map with which civil engineers are more familiar. For example, a horizontal section through the volume contours gives a profile of volumes along the length of the study area at the instant in time at which the section is taken. Similarly, a vertical section through this figure gives a profile of volume levels over the time length of the study period at a point in space on the study area. The contour figure as a whole is an excellent way of demonstrating the variation of such a parameter in both dimen­sions and therefore effectively illustrates the overall operation in the study area.

All these parameters were computed by averaging over the time interval indicated on the ordinates of these figures (two minutes in this

55

5:0

s:ot

4:59

4:57

~

eo 4:55

~

w ~

~

-4 -2 2 STATIDNS FROM NOSE

$03fl~~~ -- 26 §2-=-----==== --20 --::-~4~

5:0[ --!B 18 20

4:59

~ 4:55

~ 0 LLI 4:53 z ~

4=47

4:45

5:03

5:01

4:59

4:57

4:55

4:53

4:51

4=49

4:47

-4

-----------------28---------------

--------------26~

c=-=24~ 26

28 26

lDENSITY-V.P.M.e:-===-24

24 -26

-2 STATIONS FROM NOSE

5:03

5:01

4:59

4:57 -~ -4:55

~ ~ 04:53 w z ~

4:51

-4

5:03

5:01

4:59

4:57 i "' ;:4:55 ~ ~

~4:53 ~

~

4:51

4!49

4:47

4:45 -4

5

90

80

w 70

~ 60

~ 50

1-~ 40

~ ~ 30

20

10

5

-2

STATIONS FROM NOSE

) _..1.5

-2 STATIONS FROM NOSE

I GAP ACCEPTANC~ I ' CHARACTERISTICS ~--

' / ' / '

/ '

/ ' /

L ' /

' ' RELATIVE SPEED ,/ LOW 'SJ 5MPH

--HIGH> I 5MPH

1111111 Ill ;

-2 2 LO 1.5 2.0 6 7 8 9 10 12 14 16 18 20

STATIONS FROM NOSE GAP·SEOONDS

TRAFFIC CHARACTERISTICS DEMPSTER

TO STREET NORTHBOUND EDENS EXPRESSWA~

Figure 41

56

ENTRANCE RAMP CHICAGO

case) and over the distance intervals indicated on the abscissae. The volume is computed by simply counting the number of arrivals at each station during the averaging interval and expanding it to hourly volumes. The speed is calculated by averaging the travel times over each interval for each averaging period and then dividing the distance by this average travel time. It is therefore the time mean speed. The density is not calculated from the volume and the speed, but is computed by summing the travel times of vehicles traversing the 200 feet section during the averaging time interval and then dividing this sum by the product of the distance interval over which the travel times were computed {200 feet) and the time interval {2 minutes). The acceleration noise is computed as the standard deviation of the accelerations of consecutive vehicles over two adjacent distance intervals and is therefore based on a hundred per cent sample rather than on a single vehicle as has been conventional­ly done. The probability of a gap of greater than three seconds is com­puted by taking the ratio of the number of gaps greater than three seconds to the total number of gaps. The values thus calculated were considered to be the value of the parameter at the midpoint of the time and distance interval over which it was computed, and contour lines drawn through it ir.. the conventional manner.

The sixth diagram on the figure illustrates the gap acceptance characteristics observed at the entrance ramp during the study period. It shows the cumulative probability of a certain size gap being accepted under conditions of high and low relative speeds between freeway and entering vehicles. These relationships were derived by means of a one-variable probit analysis. This analysis is of a more specialized nature and is further explored in another paper. On some of these figures presented later in this report, only one of the relative speed lines are shown. This is due to either extremely low sample sizes in one of the relative speed groups causing the results to be unreliable or otherwise the probit analysis did not converge.

A number of other computer programs 11_ave been written for the more specialized analysis of the merging operation. These specialized programs will not be discussed in this report apart from listing them in table VIII which shows the library of computer programs written, all using the simple data format obtained by the time oriented analysis of the films.

57

Program Number

1 2 3 4 5 6 7 8

9 10 11 12 13 14 15 16

TABLE VIII

COMPUTER PROGRAMS FOR THE ANALYSIS OF ENTRANCE RAMP OPERATIONS

Descriptive Title

Check for obvious errors Plot time- space diagram Analysis of speed-density relations Speeds and accelerations of ramp vehicles Analysis of gap availability Analysis of gap stability Analysis of gap acceptance characteristics Probit analysis of gap acceptance charac-

teristics Effect of following gap on gap acceptance Effect of time waiting on gap acceptance Deviation of ramp speed distributions Deviation of arrival distributions Distributions of relative speeds Distributions of point of entry Distributions of number of gaps rejected Analysis of vehicle travel times

TYPICAL RESULTS

Below follows a discussion of the traffic operation at some of the study locations with emphasis on the effects of geometries as mirrored by the contour diagrams.

No Geometric Effect

Figures 42 and 43 illustrate the operation at two ramps in Cali­fornia. These two ramps are quite similar in the geometric features of acceleration lane length and shape, angles of convergence, grades, curvature, number of lanes and others. Furthermore, these two ramps are located in the same geographic area and both studies were made at about the same time of day. It is therefore reasonable to

58

7:31

7:25

2 0 STATIONS FROM NOSE

2 0 STATIONS FROM NOSE

2 0 STATIONS FROM NOSE

TERISTICS TRAFFIC CHARAC D ENTRANCE RAMP,

ASHBY AVENUE S~~i~~~~NSAN FRANCISCO EASTSHORE

Figure 42

59

7:47

7'4"1------_../

7:43

7=35

STATIONS FROM NOSE

7,49·-,-----------------------, ---------40, _________ ___

STATIONS FROM NOSE

7,4--=========oo:::==~-----------"J I so

7:47

7:45

---------4·---------------------------40--------------~·5-­

--- .30:===:=====

C§::=> __) ··~ ~ 25-

li~-.._ ~~~~ 2~20 ~~ ~ 7'33.:!-.---=:::::,.,,.=:----..--~.....__---,-----~-:::_ _ _j

7:47

7:45

7:43

5

0

f.--

0

0

0

0,....-

0

0

0

0 .....

5

STATIONS FROM NOSE

II GAP ACCEPTANCE I CHARACTERISTICS

----1--

......

...

4

STATIONS FROM NOSE

v v----

... _,:.-" ...

...

1--

... ...........

RELATIVE SPEEDI

1 -- ~?::. ; :g ~;~ r

1 I

' ' 4

STATIONS FROM NOSE

0.5 o• 0.7 OS 0.9 1.0 1.!5 2.0 3.0 4.0 5.0 6.0 7.0 8.0 GAP-SECONDS

TRAFFIC CHARACTERISTICS BROADWAY NORTHBOUND ENTRANCE RAMP,

FREEWAY. SAN FRANCISCO BAYSHORE

Figure 43

60

expect that the difference in operation at these two locations was caused by the traffic demand.

By comparing the two volume contours, it can be seen that the demand on the freeway was about the same at both locations but that the ramp volume was higher at the Ashby Avenue ramp. This may be the cause for the concentration of higher acceleration noise in the area near the nose of the Ashby ramp. This feature was also evidenced at other high volume ramps. Although the range in magnitude of acceleration noise is about the same at both ramps, the noise is more evenly spread out at the Broadway ramp except for a high acceleration noise spot that coincides with a sudden peak in average speed and decrease in density. Another such peak in acceleration noise is unexplained but occurred at the end of the study period, perhaps before it was reflected by the other parameters. A region of low acceleration noise also coincides with a high density, low speed area. None of these peaks and dips in acceler­ation noise are reflected in the volume contours. As can be expected the patterns of the contours showing the probability of a gap greater than three seconds resemble those of the volume contours. The prob­ability seems to be lower generally at Broadway than at Ashby, although the volume levels in the Broadway merging area are generally lower. This may be caused by the bunching of vehicles which could cause the number of gaps greater than three seconds to remain essentially the same as volume increases slightly, while the total number of gaps in­crease directly with the number of vehicles.

Another situation in which traffic demand completely overshadows the effect of geometric variables and which the reader of the contour diagrams should be watchful for, is when forced flow exists. Such a condition is illustrated in figure 44. From an inspection of the volume and acceleration noise contours one could easily, in view of the low acceleration noise, conclude that this ramp is of an excellent design. That may well be so, but an inspection of the speed and density con­tours reveal that conditions of forced flow exist, overshadowing any effect that geometries might have. Note that again the regions of higher acceleration noise correspond to the regions of lower density and higher speed. This observation bears a distinct implication re­garding the use of acceleration noise as a measure of the level of service on a facility. Another such example of congested flow is demonstrated by Figure 45. It is clear that in view of the low speeds, no observations on gap acceptance at high relative speeds were made and therefore only the low relative speed lines can be exhibited on the diagrams of gap acceptance characteristics.

These effects of traffic demand on operations in the merging area

61

5:25

5:21

i s:19

.:

~ 5:17

I!;

':'1

" 5:11

5:09

5:25

5:23

5:21

" 5:19 .:

~ 5:11

... 0

w 5:15 ~

" s:l3

5:11

5:og

5:07 -4

5:25

5:23

5:21

5:19

5:17

s:ts

5:11

5:09

s:o7 -4

5:25

~:~~ 5:23

s:e.1

5:19 ,;

" ;: 5:17 ~12 il ...

~? (? ~ 5:12 ~

" 5:13

~ I 5:11 ~ -::J 14 16 18 20 2~

---12 ~ 15:09 I sPEED ·M P.H ~ 12

14 2( s:o1

-2 0 -4 -2 STATIONS FROM NOSE STATIONS FROM NOSE

5:25

~~0~ ?/::~· 5:23

~·)] -0.50 !.Off ----200 5:21

-~J ~ .------::::::220 ~ 180

~ \._ ~ ..... 5:t9 ,; .:

~~ --0.75 g 5:17

~1805/ ~ ~ 5:t5 -·u(·-~200/ /a' ~5 "' ~ 180 160 140 I 0 I 0 " 5:13 . ~ l.O 1.25-

5 '";;;Jj) \ ~ ~-5:11 ~

075~ -----180 IACCELERATIO~I LO C0.75-I DENSITY. V.P.M.~I80 5:09 NOISE·FT./SEC2 -::g . 10o"'

5:07 -2 2 -4 -2 0

STATIONS FROM NOSE STATIONS FROM NOSE

5

GAP ACCEPTANC~ I CHARACTERISTICS

90

0 ~

;-----0

-------v 1--I--"

w 7

! 60

~50 ,_ ~ 40

~ 30

' 20 RELATIVE SPEED

10 1: LOW ,; 15M PH I --HIGH> 15MPH

~ 5 ~

-2 0.5 0.6 0.7 0.8 0.9 1.0 15 2.0 3.0 4.0 s.o ao 1.0 ao STATIONS FROM NOSE GAP-SECONDS

TRAFFIC CHARACTERISTICS LINWOOD NORTHBOUND ENTRANCE RAMP

ON THE JOHN LODGE EXPRESSWAY, DETROIT

Figure 44

62

5:0

5:10

!>08

" ~ s:o

~ IJ.. 5=04 0

w

"' j::: 5:02.

s:oo

4:58

-·

5:12

5:10

G -----~

=:) G ~

~ ____ ,.=:::::> c ~,.--,.

~~ , ..... ~· IS-., ao-

-· STATIONS FROM NOSE STATIONS FROM NOSE

&12~---------------=-------,

---75~ ~

~ ~100

r:-::=--==-::-:-1.50 1.25 ..... ACCELERATIO~oou"---::> ·--~ NOISE-FT./SEC~

10c("

~··+------.-----,---L--r-----~ -· STATIONS FROM NOSE STATIONS FROM NOSE

95

90 I I GAP ACCEPTANCE I

CHARACTERISTICS y 0

vv vv

/ /

0 / 0 /

vv RELATIVE SPEED

~ LOW 5 15M PH j --HIGH> 15 MPH 10

5 v ~

o.s o.e o.7 o.e o.9 1.0 2.0 3.0 4.0 5.0 6.0 7.0 8.0

STATIONS FROM NOSE GAP -SECONDS

TRAFFIC CHARACTERISTICS BRENTWOOD WESTBOUND ENTRANCE RAMP TO DANIEL BOONE EXPRESSWAY , ST. LOUIS

Figure 45

63

as displayed by the contour diagrams, should be kept in mind when reading the figures for the effects of geometries.

Effect of Acceleration Lane Length

The effect of the length of acceleration lane is illustrated by Fig­ures 46 and 47. These two figures were selected not only for the sim­ilarity of general geometric features other than acceleration lane lengths of the ramps to which they apply, but also for the similarity in the ranges of speeds and densities. The freeway volume was lighter but since both merging areas were operating at similar speeds and densities, the effects of the traffic demand on the acceleration noise will be minimized. Perhaps the most striking difference in the oper­ations of the merging areas is the general smoothness of flow at the ramp with the larger acceleration lane as exhibited by all the contour diagrams. A comparison of the volume contours clearly reveals the gradual increase in volume level over the length of the acceleration lane of the Coldwater Canyon ramp as compared to the sudden increase over a short distance at the Dumble ramp, resulting in considerable turbulence in speeds and densities. This turbulence caused the higher acceleration noise observed at the Dumble ramp. Even the probability contours display this smoother operation at the Coldwater Canyon ramp. These two figures form a good demonstration of the desirability of the longer acceleration lane.

The operation at a high volume ramp with a very long acceleration lane is illustrated by Figure 48. Notice that although the acceleration lane is 1200 feet long, by far the largest proportion of ramp vehicles chose to enter the freeway within the first 400 feet. This type of opera­tion was also evidenced by other studies at this and another similar ramp. However, in spite of the extremely high entrance ramp volume, high speeds were maintained and the acceleration noise remained at a low level.

Effect of Angle of Convergence

In order to demonstrate the effect of the angle of convergence two sets of data were selected that was gathered at ramps with geometries that differed mainly in the angle of convergence, during periods when speeds and densities were fairly comparable. These are shown on Figures 49 and 50. The Wayside entrance ramp with the higher angle of entry seems to cause a more sudden increase in volume levels over a shorter distance than the Milbrae ramp with the smaller angle of

64

STATIONS FROM NOSE

--49

4:18 =:----48~

4=14

~'-:_;;;;­~~~ ~:~

4

,

10

I SPEED-MPH. i -- -49~ 4:081t----,.----....----,-----,.------.,

-4 -2

STATIONS FROM NOSE

4,20>.,------------------------,

4=18

4:1

4:10

-4

~--------------------<::::::_32 __

------35---------------···------------~ -----------···-----------------------35--

----32~

-2

STATIONS FROM NOSE

41

414

4:12

4:1

95

90

80

~ 70

~ 60

~ 50

lz 40

~ ~ 30

20

10

5

-2

4.0--

6.0--

STATIONS FROM NOSE

I % GAP ACCEPTANC~ I v'-11 I I CHARACTERISTICS

! I ~f/ i ! !

--~-;-,- - r~ ~

'

I ~-+----__ .. I

i I ! I

~ ~-- ~ i

----- - --' / I I ' I -

/ I j

/ v i I I I

I I RELATIVE SPEEDj

I 1 l LOW" 15MPHj --HIGH> 15M PH

I ~ .:l

0.5 06 0.7 0.8 0.9 1.0 1.5 3.0 4.0 5.0 6.0 7.0 8.0

GAP-SECONDS

TRAFFIC CHARACTERISTICS COLDWATER CANYON AVENUE WESTBOUND ENTRANCE RAM~

VENTURA FREEWAY, LOS ANGELES

Figure 46

65

4:26 ~~ :~c.____~_ 500 3 600

::0~-~: F'ooo= 1200-

4:24

I VOLUME-V.RH. ~ 800~ 1000 c:: ) 4:12

4:10 -5 -2 ., 0

STATIONS FROM NOSE

.,28 r----:;_,..-----------.----------;r---,

STATIONS FROM NOSE

5

0

eo

0

0

0

0

0

0

0/

5

STATIONS FROM NOSE

STATIONS FROM NOSE

GAP ACCEPTANC~ I /v CHARACTERISTICS

/

/ v ,

/i , ,

/ -,

v -, ,

v , , , ,

/ , , RELATIVE SPEED , , ~~-~?~: :;~~~ , ,

--,

I , g -,

·4 -3 -2 -1 0.5 0.6 0.7 0.8 0.9 lO 1.5 20 3.0 4.0 5.0 6.0 7.0 8.0

STATIONS FROM NOSE GAP-SECONDS

TRAFFIC CHARACTERISTICS DUMBLE EASTBOUND ENTRANCE RAMP

ON THE GULF FREEWAY, HOUSTON

Figure 47

66

7:58

-2 2 4 10 STATIONS FROM NOSE

8<>6

9:02

8:0o

7:58

7:56

~~-"c:: .. c-: ~ 47~) ~). -.. r 46 __--J

~~~ ""'' ~· 46

7t52 47

48 46-

-4 -2 2 4 STATIONS FROM NOSE

10

8•08,-------------------, 8t08-r---=-----.:-------,----.-----------,

~ 1.50 2.0 2.5

8:06 ~40----~45--------------

8:04 ~

8102 -45

-----45 ~ 8:oo

--------------4·-----------7:56

-==:~ ======- 45 -------~so __ _

~ ~45---•o _____ __

40

30------7'52 IDENSITY-V.P.M.I=

25 ~ 30 35

45 7:50 -4

8:08

8t06

804

8:02

8:00

7:58

7:56

-2

.70

2 4 STATIONS FROM NOSE

.30 I \__-.30

8:04

9:02

8:0

7:58

7:56

10 -4

5

0

0

0

0

ov 0 ~~

0

5

~~·~~=l2D ) \ ~2D

-2.5-z.:~

2o ~Q) ~1~::_ \~~20 2.5-

6~ -2 2 4

STATIONS FROM NOS£

GAP ACCEPTANCE I CHARACTERISTICS I

I f-:>

!---"" f.--------- --~-

.------::. , ...........

---~ ....... ""

--- I I - I -~ I

I I

I RELATIVE SPEED

LOWS /5MPH --HIGH> 15 MPH

i I

10

~

~

! 7:5o_+-4-~_2-~~-4-2 -'-_t___,--;>==-----~---l10 0.5 Q6 0.7 0.8 0.9 1.0 1.5 20 3.0 4.0 5.0 6.0 7.0 8.0

STATIONS FROM NOSE GAP-SECONDS

TRAFFIC CHARACTERISTICS LONG ISLAND EXPRESSWAY NORTHBOUND ENTRANCE RAMP

TO CROSS ISLAND EXPRESSWAY , NEW YORK

Figure 48

67

t------eoo-------4,24J------'ooo-----_.

4:22 l VOLUME-V.P.H. I

•2

STATIONS FROM NOSE

~••r---~============~~.~o==============~~

4:32

~ 4:30

~ 4:28 IS

----------35----------·0------~

---2·-------

::::::::::::====~~===============

STATIONS FROM NOSE

STATIONS FROM NOSE

., .. ,------------------------------""""..,------, :::::::----. -----------==-49 ~

:::_____~ ----......,------.,.o.

_____/"0----

------··~ .. ~ ~ ~

.,22~----~··=-------4:2ot-------,-------,-___:;;•.:.o ----.-==------.-------1

4'24-

-· •2

STATIONS FROM NOSE

.,....,. __________________________ ===---------,

~~ [~

.,

4:28

4:26 [?

<C STATIONS FROM NOSE

95

GAP ACCEPTANCtl

v/ CHARACTERISTICS

90

80 v ,

/ ,

0

/ ........ 0

,

--/ ,•' 0

/ ,•' --0

v.v ,

........... 0 , RELATIVE SPEED v ,•

1: LOW S 15M PH ,• 0

,- --HIGH> 15 MPH ,- II

5 0.5 0.6 0.7 0.8 0.9 1.0 1.5 3.0 4.0 e.o e.o 1.0 e.o 2.0

GAP- SECONDS

TRAFFIC CHARACTER ISTJCS

MILBRAE AVENUE SOUTHBOUND ENTRANCE RAMP BAYSHORE FREEWAY. SAN FRANCISeO

Figure 49

68

4:07 f-------

~ 4:05-j--------

1------800

3:57 VOLUME-V.P.H.

4:07

4:05

4:03

4:01

3:59

3=57

3:55

4:11

4:09

4:07

"' 4:05

~

~ 4:03

i';

!!! 4:01 ;=

3:59

3:57

-4·~ ~.If~~

c4o­L_ .ca=.

>-~.J ~. -~ ~[J·44 G~~

SPEED-M.P.H. 42

_

3:5!5 +-~==-r-4-'--6----4

--'5

'-,~44

----.;:.::.::-4

-5

-"'-....::~~·-·~-==~--·-·-.==-=----j STATIONS FROM NOSE

STATIONS FROM NOSE

0.50

-3 -2 -1

95

90

0

~ 70

t 60

tJ 'I 5 0

>-0

'" 4

~ 30

0

10

I GAP ACCEPTANCE; I CHARACTERISTICS

I

!

/

L /

v I

v ,

, ,

STATIONS FROM NOSE

STATIONS FROM NOSE

! . I / l

,

! v II, ,

I

/y ,

,

v ! ,~ , I

, ,

l I ,

I ,,

I , , REL ATIVE SPEED

, , LOW~ 15M PH , -- H IGH >IS MPH

II 1111111

~ ;

5 1.0 1.5 2.0 4 5 6 7 8 9 10 12 14 16 18 20

STATIONS FROM NOSE GAP-SECONDS

TRAFFIC CHARACTERISTICS WAYSIDE EASTBOUND ENTRANCE RAMP

ON THE GULF FREEWAY, HOUSTON

Figure 50

69

convergence. This causes a greater turbulence in speeds and densities resulting in a generally higher level of acceleration noise at the Way­side ramp. This may be partially caused by the traffic demand since the freeway volume upstream of the nose is generally lower at the Wayside ramp, giving a higher ratio of ramp volume. However, com­parisons with a study period at Wayside when the freeway volumes were higher, such as shown in Figure 51, it can be seen that speeds generally decreased and densities increased resulting in a slightly lower accelera­tion noise which was still generally higher than that at the Milbrae ramp.

Figures 52 and 53 serve as another illustration of the effects of the angle of convergence. In this case the ramp geometries differ again mainly in the angle of convergence but both are of such high type designs that the value of five degrees as against eleven degrees, per­haps give a wrongful impression of the actual difference.

By inspection of the contour diagrams, it can be seen that volumes, speeds and densities were comparable during the study periods at these two ramps. The resulting acceleration noise at the 69th Road ramp with the lower angle of entry seems to be generally lower than at the Peterson Avenue ramp. However, the difference in ramp profiles should be noted and may lead one to conclude that the effect of the difference in angle of convergence at these two ramps is not noticeable in the contour diagrams.

Effect of Grades

Figures 54 and 55 demonstrate the operation at two ramps that are remarkably similar in most geometric aspects. Both have 1200 feet long parallel lane type acceleration lanes with ramps converging at one degree at the nose. They differ only slightly in the grades along the acceleration lane, in that the Jericho ramp is slightly downgrade and the Long Island Expressway ramp slightly uphill.

The general pattern of operation is also remarkably similar at the two ramps as evidenced by the contour diagrams. At both locations, most of the ramp vehicles entered the freeway within the first five to six hundred feet of the acceleration lane length. The total merging volume at the two locations were comparable, but the ramp volume at the Long Island ramp far exceeded that at the Jericho ramp, giving rise to slightly lower speeds and higher densities, resulting in a high­er level of acceleration noise. Because of this uneven split in the traffic demands, it is difficult to isolate the effect, if any, of the slight

70

STATIONS FROM NOSE

!5:10

5:08 ~ 26---

) -~~-= 5:06

5:04

5:02 ~ 36 34

5:00 ~-~ ~ rr3·

~--4:58 :;t

/

QJr c 4:56

4:54 I SPEED-M.P.H. I 4:52

/"' -3 -a -r

STATIONS FROM NOSE

S:IO.,...-----....----=---~-------~

~~ .. h "!(_ S:08

5:06

S:04 i "' >- 5:02 ~=~\_ss

~~C.: ~ ~ 0 1>.1 s:oo . ~

4'54

iNOISE-FT./SE&.I jrA:-:C:::cCE;:;-L-;oER"'A"":n"'ON;;,.[I ) ?'"

5.0_ )'·,f 4:62_-!-3---.• c------,_,-"---T"""---T----''---,-----!

5

90 I GAP ACCEPTANC~ I CHARACTERISTICS

0

0

i 0

I 0

!

0 / v / /

10

/ 5

1.0 '

/ /

1.5 2.0

STATIONS FROM NOSE

I' I I ~~-I v I

' I (

"'i

I' lv ({"' I

vr ' ' ' ! i

v ' f i i I '

' /

' RELATIVE SPEED '

LOW :S 15MPH II -- HIGH >IS MPH

II 1111111 ! Iii= i

6 7 8 9 10 12 14 16 18 20

GAP-SECONDS

TRAFFIC CHARACTERISTICS WAYSIDE EASTBOUND ENTRANCE RAMP

ON THE GULF FREEWAY, HOUSTON

Figure 51

71

i

i ~

~ ~

"' ~ >=

1----1200

4,11 f----1100----------­

t.----tOOO----------

! 4:05

4:01

-4544

----------~·2::::::::::::::

,~ -----.2 _____ _ ------:;---..

ISPEED-M,P.H) ,......-~ 3:59+--------------~-----~-----l

4:13

4:11

4:09

4=07

4:05

4:03

4:01

3:59 -4

-2 -· -2

STATIONS FROM NOSE STATIONS FROM NOSE

38 34

.,,. ,--------------.------------, -1.5

---------30 4:1[

--------30~~~~~~~~~~ ---------34

~40 = 4:09

---------3·----------4:07

4:05

1.7!5 ____ _

---------3·------------~·2

38

2,0...------

----------3., _________ __ IDENSITY-V,RM,I

30-

4:01

~28 ______________ __

,...2s--2

STATIONS FROM NOSE STATIONS FROM NOSE

95

90 I I

RELATIVE SPEED

~~HIGH >tOMPH 0LOW <lOMPH

f.-" 80

----~----- i ..-----v II

------------

I! I

20

GAP ACCEPTANCE 10 CHARACTERISTICS

' llllllllll z 5

1,0 1,5 2.0 2.5 3.0 3.5 4,0 4.5 5.0 5.5 6.0

STATIONS FROM NOSE GAP-SECONDS

TRAFFIC CHARACTERISTICS 69th

ON THE ROAD SOUTHBOUND

GRAND CENTRAL ENTRANCE RAMP PARKWAY, NEW YORK

Figure 52

72

2___ 4'41 VOLUME~V.P.H. 900

~=::;...;;;.;.:.;;.r--

4=45

4=43

4=51

:i ~

~ 4=49

~ ~ 04:47 w ,. ~

4=45

4=43

~c:::: -49 ~::= -4·~==-========::_-__

isPEED-M.P.H.l 48

-49 .. 4:39+-----"-:...,;-------..,::>~-----,;--------,------j

STATIONS FROM NOSE

4•57,--=--....==:c33.,24==----~-----::::;3~4======,_..-~-, 4=55 \. J

~ 4=49

~ 0 w 4:47 ,. ~

4=45

4=57

4:55

4=53

4:51

" ~ ~

4=49

l'; 4=47

w ,. ~

4:45

4=43

4=41

·4

.45

34 32 30

=25==== c:25:

~~·4 ---------34---

·2

STATIONS FROM NOSE

4=51

i " ;: 4=49

1l ~

~ 4=47 ,. ~

·4

95

90

•2

STATIONS FROM NOSE

~ ~25-

)~.0 2~.5 ~::c. 1.75-

2.0--

2.5-

--3.0 2.5-

STATIONS FROM NOSE

11 ' w ~AP ACCEPTANa; l ! i CHARACTERISTICS

tr' w 7 !;!

~ 6

~ 5

>-

--- f.-- ll I I 0 '

-------I I '

0 ----------' i I 0 '

' ' I

80

~ 4

~ 3

0

' ' i 0

' ' I I 0

' ' REL ATIVE SPEED

' ' I LOW,; 15MPH

0 ' --HI GH > 15MPH

' I II 1111111 5 '

~ I I . i

il F

i I l!

I

I: 4=39-~

·4 ·2 15 2.0 6 7 8 9 10 12 14 16 18 20

STATIONS FROM NOSE GAP- SECONDS

TRAFFIC CHARACTERISTICS PETERSON AVENUE NORTHBOUND ENTRANCE RAMP

TO EDENS EXPRESSWAY, CHICAGO

Figure 53

73

0: ..... 5:26

~ .. 0 524

!l! ;::

"' ~ ~ l5

"' " ;::

-4

5:34

!):32

5:30

5:28

5:26

5=24

s:zz

s:zo

s:1a

5:16 -4

5!34

5:32

5:30

5:28

s:zs

5:24

5:22

5:20

S:IB

5:16

-4

-2 STATIONS FROM NOSE

XR 4o

---30

30 32

34 36

38 c=4o 36

38

-36 -2

STATIONS FROM NOSE

5:30

~s:zs

"' "' ~ 5:26

.. ~ 5:24

"' ;:: 5:22

5:20

5:18

,,,. +------,-----"::::::_-,--"'::::_---,--_L-,------,-----{ -4

-4

95

90

80

~ 70

" ~ 60

~ 50 1-G:i 40

~ ~ 30

20

0

v

-2

-2

GAP ACCEPTANC~ I II CHARACTERISTICS

v v v

l.L 1-- f---

STATIONS FROM NOSE

2 STATIONS FROM NOSE

I

v-f/ /

// /

/ /

v /

/ /

/ /

/ RELATIVE SPEED / LOWS 15M PH

/ --HIGH> 15MPH

/ /

; '

-2 0 2

5 0.5 0.6 0.7 0.8 0.9 1.0 1.5 2.0 4.0 5.0 6.0 7.0 8.0

STATIONS FROM NOSE GAP-SECONDS

TRAFFIC CHARACTERISTICS JERICHO {Rt 25) EASTBOUND ENTRANCE RAMP

NEW YORK ON LONG ISLAND EXPRESSWA~

Figure 54

74

8:36

8:34

8:32

8:26

8:24

8:22

8=20

8:18 -4

8:36

8:34

8:32

~ 8:30

~ 9:28

~ 0 8:26 w

" " 8:2

8:2

8=20

8:18 -4

" ~~ 46 ., ~~ ~ ~43 42 44

-40~ ~c_-

~~ ~ .. ~ :t

~"~-~ \ :: 2?) }_)'~ 3o ~-

40-- 46:::-----: 44 '45

8:18 -2 10 -4 10

STATIONS FROM NOSE STATIONS FROM NOSE

8:36

c=-===36- 8:34

4 48

8:32 c==-=-52~

~~ ~!~======== 8:30 c:2.0

~46 46-

~~ 8:28

·3o G /. 8=26

2.5 2.0~2.0 8:24

48 46 48

~ .. 44 40

36 8:22

40 36-44

loENSITY-V.P.M.p46 48 48-............ 8:20

2.0 2.0 ~ 7 ---50--2.5 3.0

9:1a -2 10 -4 -2

STATIONS FROM NOSE STATIONS FROM NOSE

5

i ' I I I II I I

II GAP ACCEPTANCE I I I I I

I ' i i! \ CHARACTERISTICS

i I ! I I j_ I I

I I I I

i i i rl I I ' I , · I I

80

i I i )---11 ! I i

0 ! ~!'""! i I ....---~ ! J~ ~--~ i i 0

Vi .......... i I

I ~

I ~ ~~

............... i ~

I II / ~ i

~-

i I I ~-~ I . ' ~

~ I RELATIVE SPEED / 1: LOWs 15MP~ I I --HIGH> 15M PH

I !

5 i

4

STATIONS FROM NOSE

10 0.5 0.6 0.7 0.8 0.9 1.0 1.5 2.0 3.0 4.0 5.0 6.0 7.0 8.0

GAP-SECONDS

TRAFFIC CHARACTERISTICS LONG ISLAND EXPRESSWAY NORTHBOUND ENTRANCE RAMP

TO CROSS ISLAND EXPRESSWAY, NEW YORK

Figure 55

75

difference in grades. It does seem, however, that at the upgrade ramp, vehicles entered the freeway generally sooner than at the Jeri­cho ramp, which may well have been caused by the grade.

Contour figures such as those discussed above are available for each study period at each study location; eighty-three in all. In order to include at least one such figure for each study location, the opera­tion at ramps not discussed above are illustrated by contour diagrams included in Appendix A.

COMMENTS

1. An aerial photographic technique has been developed for collect­ing large masses of comprehensive traffic data with relative economy.

2. The manner and mobility of the photographic technique makes it generally applicable to almost any study site located anywhere.

3. Since no distances are measured off the films, the study technique is not dependent on maintaining a strict flight altitude or flight path and is not affected by highway elevation changes.

4. Problems encountered in the filming studies included the mounting of the equipment in the aircraft, development of the proper flight path, evaluation and acquiring of the proper hardware and software and coping with the changing light conditions during circling.

5. Problems encountered in the data reduction included the careful training of film analysis personnel, lack of definition in some films and the problem of missing data points.

6. In the study of the effects of geometries on traffic operation, care should be taken to avoid periods of forced flow.

7. Time- space diagrams of vehicles paths such as illustrated in Figure 40 of this report, not only reveals the operation on the facility at a glance, but is also an invaluable aid in the editing of data, the writing and debugging of more complicated computer programs and in meeting the problem of missing data points.

76

8. Contour diagrams are an effective way of illustrating the opera­tion of a facility on a continuous basis in both time and space.

ACKNOWLEDGMENTS

The success of this phase of the Project with the national scope of its field studies is due to a large extent on the cooperation of the Federal Government, six State Governments, and many local gov­ernmental agencies. The following partial list of personnel, their staffs and agencies is offered:

California Division of Highways - Mr. Jamis E. Wilson, Mr. Karl Moskowitz and Mr. Leonard Newman

Illinois Division of Highways - Mr. Charles H. McLean

Michigan State Highway Department - Mr. Joseph Marlowe

Missouri Highway Department - Mr. James Little and Mr. James Roberts

Texas Highway Department - Mr. Dale D. Marvel, Mr. John N. Lipscomb and William V. Ward

Detroit Department of Traffic - Mr. Alger F. Malo

New York City Department of Traffic - Mr. Edward Bonelli

Deserving special mention is Mr. Joseph W. Hess, Acting Leader, Improved Utilization of High Speed Highways Task Group of the U.S. Bureau of Public Roads. Mr. Hess, who was instrumental in defining the scope and direction of the Project in the Project Prospectus, has helped greatly in making contracts with local agencies and selecting study sites. Also greatly appreciated is the work of Mr. W. R. McCasland in making preparations for many of the Houston studies and to Mr. James Bradley, Motion Picture Production Technician, whose fine work meant a great deal to the success of the project.

77

APflENDIX A

CONTOUR DIAGRAMS OF THE OPERATION AT RAMPS

NOT SPECIFICALLY DISCUSSED IN THE REPORT.

4:30

:::n~~:?~~~~~~.!.g_ ~ 432 ~ 4:30

4:28

4:26

4!20 I VOLUME- V.P.H. I BOO

:r--==~c@ 4'20 I SPEEO-M.P.H. I' •• ··---50~ •:r•+--------,----------,,-------.--=="T=--=---=;:==--_J

-2 -4 -2

STATIONS FROM NOSE STATIONS FROM NOSE

---45

4:22 ~ 4:20 ~35-------.....

~-~==~====~~~2~·==~=====;~~--.-----J 4:Je+ -4 -2

STATIONS FROM NOSE

STATIONS FROM NOSE

STATIONS FROM NOSE

~ ::I-------+---+---=--~-<_J"+-1-+1---t--t-1·-t-if--,t-11 Vf-i'HI --+,'+I, t-t--f--1--t-IHi--t-t-'-mi

§ sof---~+ 1, ~/+. -+I-+! -+-+1 +1--if!-1 '+r·'+t-r +I +++ii -H-+HJ+I ++' If+< - ...V"... ' I I ' ' I " ,.., i /• I ! I I ~ 40v /, II ~ 30f------i----t---l-_,-.1.cL-HH-+t-1 +-+++t+i-1+++-++++++H

Of--------t----t~''-t-----t--t----t--t---t-t-++~RE~L~A~TI~V~E~S~~ED~++~

0 , , , , , 5 1.0

, / -- ~?~: :~~~~

1.5 2.0 4

GAP-SECONDS

Ill 1111 7 8 9 10 12 14 16 18 20

TRAFFIC CHARACTERISTICS LAKE SHORE

McARTHUR SOUTHBOUND ENTRANCE RAMP, FREEWAY, SAN FRANCISCO

Figure 56

79

4•36

4•34

4•32 I VOLUME-V.P.H.J

STATIONS FROM NOSE

30 25

~------~ 30---------------1 DENSITY-1/.P.M.!-- ---::::::=:::::

=--------35 _____-::40----:;::::: 4•30•-l---~---~--~---~--~-----· -4 -2

STATIONS FROM NOSE

4•46

4>32 I SPEED-M.P.H. I -55

4•48

4•46

4•44

4•42

4•40

4•38

4•36

4•34

4•32

4•30 ·6 ·4

5

STATIONS FROM NOSE

STATIONS FROM NOSE

GAP ACCEPTANC~ I CHARACTERISTICS

90

0

-----1--0

----0 ,.- ' _..!-- '

01--' '

/ 0

/ 0

/

' 0 ' ' L RELATIVE SPEED

' ' ' l LOW< ISMP ~1 ' ' --HIGH> 15 MP 0 ' , , J , ,, , 5

'

! '

O.!i 0.6 0.7 0.8 0.9 l.O ,. 2.0 3.0 4.0 s.o 6.0 7.0 8.0

STATIONS FROM NOSE GAP -SECONDS

TRAFFIC CHARACTERISTICS MONUMENT JUNCTION SOUTHBOUND ENTRANCE RAMP

ON I 680 IN PLEASANT HILL (SAN FRANCISCO)

Figure 57

80

STATIONS FROM NOSE

34

28 30

STATIONS FROM NOSE

~

~ 4:08

g ~

~ 4:06

~ ;:

4:04

4:02

4:00

4:10

4:08

4:06

4:04

4:02

4:00

95

90

80

20

10

5

-2

STATIONS FROM NOSE

.::> 3.0 2.5 2.0

-~~ --255/ c=L5-----2.0

/20------2

STATIONS FROM NOSE

I

II GAP ACCEPTANC[ I CHARACTERISTICS L.)./ i

I 1/ v I J7

v I I/

1...-v vv

RELATIVE SPEED

i• LOW "15M PH I -- HIGH> 15 MPH

' 0.5 0.6 0.7 0.8 0.9 1.0 us 2.0 3,0 4.0 s.o s.o 1.0 ao

STATIONS FROM NOSE GAP- SECONDS

TRAFFIC CHARACTERISTICS COMMUNITY DRIVE EASTBOUND ENTRANCE RAMP

ON LON~ ISLAND EXPRESSWAY, NEW YORK

Figure 62

85

r---------- 1000-----

r---------lloo-----5:38

12.00

-2 0 STATIONS FROM NOSE

5:4Qr-----======== ... ========-, 25

----------3o-----------5:38 ---------3·------------5:36 ----·0

!DENSITY -V. P.M.I

-~ --·· -- /40-

5,30+------~----~----...:..------1

-· -2 STATIONS FROM NOSE

5:401====:ao.A,•s>=::::=~-----------::;r----;Tl

:..------ 0.40 ------------------

53s-J------0.35 ----------

i

"'•o,--------------------~

i . e. 5:36

~ !5 ~ 5'34 ;::

32

---------··-------------------------··-----------------·· -----------·2---------------------·o----------

-----... .. ::~

''~"'"---: ""\ ,,,o_-±-.------~2-----=-----,-----~----__.j STATIONS FROM NOSE

5'4o,-------------.----------, ------~·___) (

5:36

5:32

1.5

~

------~·~ Ol ~ 15

15 /

I ACCELERATrO~ "-....___ L-----INOfSE-FT/SEC. 20 ~

' 5:3o_+-4 -----_~2----~----------1 STATIONS FROM NOSE

95

I

GAP ACCEPTANCE I I I

I CHARACTERISTrCS

90

80

I:

I ~ 5:36

tl 70

~ 60

tl :;/50

~ ~ 0

"' ~ 5:34 e;>

-2

0.30 0.20

" I

>-

030~ ( 0.20

0.30 \ _....-----

",

" " ""' """

i:j40 ~ ~ 30

20

10

0.5 0.6 0.7 QS 09 1.0 1.5 2.0

STATIONS FROM NOSE GAP-SECONDS

TRAFFIC CHARACTERISTICS BROADWAY NORTHBOUND ENTRANCE ON

THE NORTHERN STATE PARKWAY. NEW YORK

Figure 63

86

I: RELATrVE SPEED I -LOW,; f5MPH --HIGH >f5MPH

I It 3.0 4.0 5.0 6.0 7.0 8.0

4:24 4!24

--(;39 38 cs 4:22 4:22 _L 39-1600 38-

4!20 4:20 ___.--:38 ~a6-

4:[8 1400

\~ ! 4![8

~ 4:16 4:[6

3736 ~ ~

~ 4:14 4:14

~"~ . >=

4:12 4:12

4:10 4=10 ~ 37 C=-= 3

·-

SPEED-M.P.H. ~ 4:06 4:06 .... 37........ /37-::-

4:06 1500-

4:06 -4~9.:--- as.........,

-· -3 -2 _, -4 -3 -2 _, STATIONS FROM NOSE STATIONS FROM NOSE

4:24.,..--_=:._=:._=· =~-----------------, ~24.,....----~Tn.~----------~---~

~ 4:18

g 4:16

4=10

4:08

4=24

4:22

4:20

4:18

4:16

4:14

4:12

4:10

4:08

4:06 -·

0.15

0.25

-3

00 ~0-: t:._ ~

~3.0--....... 4:0~-~-. --_-c3--_'T2==,_,~--,-----,-'---y----cc---!

4:12

STATIONS FROM NOSE STATIONS FROM NOSE

5

J II! 1 II' !lH'r I ! ;,r; 0 I GAP ACCEPTANCE I I

I I i ;[11!! I I )-: II

II CHARACTERISTICS

~ ili ,,! , I !

0

H' i i I ,.J,r I' I jl . ' I I I I : !'

0 I A', 11' ~1! \II,

0 'I I.' /'

I 1/ I, li'X I i I i 0

/ I I II 1[: I' i I 0

/ I )'

I IIi i 1

1 i! " 0

Vr ' I II II II: 1! li1 '

_,..--0.2~

v ' ' RELATIVE SPEED ! j I

' LOW~ 15M PH I''' I 10 / ' --HIGH> 15 MPH i '·

,/ ' ' 1,1111 II 11111 1.0 1.5 2.0 6 7 8 9 10 12 14 16 18 20

STATIONS FROM NOSE GAP-SECONDS

TRAFFIC CHARACTERISTICS TELEPHONE EASTBOUND ENTRANCE

ON THE GULF FREEWAY, HOUSTON RAMP

Figure 60

83

~ 4:!58

~ 4:56 1------------!:l! ;::

•4 ·3 •2 "I STATIONS FROM NOSE

5:04

5:02

......, 5:00 ,. "' i 4:58

~ 0 4:56

~

•5 ·4 .. ·2 •I

STATIONS FROM NOSE

5:o6,---=5o.2 ,.--------::;;;;.===-~=='Slsso-~=o::----, 5•os,-------...-----------._------,

5:04

5:02

8 4:58

~ ~ 4:56

" 4:52 ---40·-----:::::;::,

~~~~~-----45 ______________ _ 4•50 I DENSITY-V.P.M.I 45'---=-.::=:::5:::0=-===:5:2::::

1-~==~====~====~~40~==~~-~--~==~-4 4!48 -s -4 -3 -2 -1

STATIONS FROM NOSE

5:04

5:02

95

I GAP ACCEPTANC~ I CHARACTERISTICS

90

0

...

v 0 v / ov

z 40 ~

10

5

........

-2 -[ STATIONS FROM NOSE

'

II i! 1: I'

/ i :i v i i I

II I I ' '

' REL ATIVE SPEED I ' ' LOWS 15M PH

' -- H IGH > 15MPH

' II 11111111 I!

' ' 1.0 15 2.0 6 7 8 9 10 12 14 16 18 20

STATIONS FROM NOSE GAP-SECONDS

TRAFFIC CHARACTERISTICS BROAD STREET EASTBOUND ENTRANCE RAMP

ON THE GULF FREEWAY, HOUSTON

Figure 61

84

7:31 8 0

7:29

7127 I VOLUME-V.P.H. ~0\

STATIONS FROM NOSE STATIONS FROM NOSE

r:43~---3-0=---------~=="3"'o===~--.

7!41

---w--------------------3o---=

-3o ----------------------w ----25 2s--

~ --25---25-------

c=========30-3o-7:31

-25 25-

7:29 ..::::::::::==22~ 22-:::::::

-zs----------zs-

1 OENSITY-\IP.M.l c::....._:::=:;-30;;-:===== ....----_25---- 25--

7:25+---~--~----""-....,---'=---,---.,.-~=T----! -e -4 -2 o

STATIONS FROM NOSE STATIONS FROM NOSE

5

I GAP ACCEPTANC~ I I

! CHARACTERISTICS

90

0

j__ e-- ,

----- ~-O!----- , '

-------,

'i 0

~ ,

:I -- , 0

i , I , 0

I , : , i 0

:1 , , , I 0

RELATIVE SPEED

II ,

, / 1: LOWs 15MPH I , --HIGH> 15MPH 0

"/'""" Jl 5 0.5 0.6 0.7 0.8 09 1.0 1.5 2.0 3.0 4.0 5.0 6.0 7.0 8.0

STATIONS FROM NOSE GAP -SECONDS

TRAFFIC CHARACTERISTICS

WATT AVENUE SOUTHBOUND ENTRANCE RAMP ON 180, SACRAMENTO

Figure 58

81

4:09

.- 4:07

" "'

4:07 :::J ~·~(

~ 4'05 , ________ _

~

~ 4:03 i==============:.:::::_ ___ :; ~

4:09

" 4:07

~ g 4:05

:s llJ 4:03 ~ ~

3:59

4:13

4:11

4:09

4:07

4:05

4:01

3:57

3:55

·3

0.45

4:01

~

r.:::-::-::'~~=-=-=-::-=----==~4~·::::---------: 42--

~~~~~~~=~=--~(~~ 3"55 +-----= •I •4 ·3 .. ·I

STATIONS FROM NOSE STATIONS FROM NOSE

•I

STATIONS FROM NOSE STATIONS FROM NOSE

95

90 H GAP ACCEPTAN~ I // CHARACTERISTICS

/ 80

w 70 u z

i 60

50

~ 40

~ 30

/ v

v /

v / v '

' ' '

20 I RELATIVE SPEED

10 1: LOW"' IS MPH I --HIGH> 15MPH

' , , ~ , 5 0.5 0.6 07 0.8 0.9 1.0 1.5 2.0 3.0 4.0 5.0 6.0 7.0 6.0

STATIONS FROM NOSE GAP-SECONDS

TRAFFIC CHARACTERISTICS CULLEN EASTBOUND ENTRANCE RAMP

ON THE GULF FREEWAY,HOUSTON

Figure 59

82

7:21

7:19

7=17

7:15

i ~

7'13 g ~ 0 7•11 ~ ~ ;::

7=09

7:07

7:05

7:03 ·4

7=21

7:19

7=17

,. 7=15

~

g 7:13

l5 ~ 7=11 ~ ;::

7:09

7=07

7:05

7:03 ·4

7=21

7=19

7=17

7:15 ,. 5 g 7=13

l5 ~

7: II ~ ;::

7:09

7:07

7:05

1400

1300 1200

1100

1200 1300

1100

I voLUME -V.P.H.~

·2

STATIONS FROM NOSE

34 36

38

36 38 34

32 30 28

28 ::;=:::>

32 34

36 38

36 34

32 30

28 ~ 26

loENSITY-V.P.M.~ 24

22---

·2 STATIONS FROM NOSE

~~------7=19 c: 46--7•21~~~l

.::: = c~~ ~7=13 -----.-0-~-, cso====::::::=-::. ~

;711 ~ c49

~·~s.s4~ 7=09 ~

-=========:::·~0 49~ - ~ 7•07i=-~~

51 50

7=05 49

48::-=-=:> --.... I SPEED- M.P. H.! 49

51 50

7:03 ·4 ·2 0

STATIONS FROM NOSE

7•2l,----------,'.s7o_;_ /-"7---'--_.--,_7-5------, 7=19

----1.75

7=07

7=05

-----~- _/ :t.Q-2.5~ 2.0

::____, ~ ~ /2.0

r 2.0 ...

,.--------:::::~:gy ~3.0~ ~~-~~

2.0~ -r.7s~c--t.so

.-2~ c:;:;;;:> --I",A"'c"'c"'E""L"'E;::RA"'T="I;;;;ON""Hv.. ---'-75 INOISE-FT./SEC~I 1.1sf 2~

-1.75 7:03+-----,--------.------.----~-----1

·4 -2

STATIONS FROM NOSE

5

llGAP ACCEPVINCEJ CHARACTERISTICS v-- ------

90

eo

~ r- .. t- .. .. .. .. !

0 .. .. / ......

0 ..

.. / I RELATIVE SPEEDJ

,/ 1: LOW < 15 MPHJ 0

.. --HIGH> 15MPH / .. ..

5 ~

·2 0.5 0.6 0.7 0.8 0.9 1.0 1.5 2.0 3.0 4.0 5.0 6.0 7.0 8.0

STATIONS FROM NOSE GAP-SECONDS

TRAFFIC CHARACTERISTICS WARREN AVENUE SOUTHBOUND ENTRANCE RAMP

TO THE SOUTHFIELD EXPRESSWAY, DETROIT

Figure 68

91

i ~

.,.,J~~~~ •• •• 30

.,.. 20---

5:19

5:17

13 ~10 ____ _

- ~ ~> ~0 10~

~ -~·

"'" lsPEED-M.P.8:1)

.,19+----------.--------~----------~--------_j -· -2 STATIONS FROM NOSE

5:21

-0.75·--------;: 5:19 g

~1.0-----.. -1.0~

-oMb .75=::> ___ 0.75

::5 ~:m

~

STATIONS FROM NOSE

5

0 I GAP ACCEPTANC~ CHARACTERISTICS

0

0 _.-1----v

0 v ---0

0 REL ATIVE SPEED

LOW ,; 15MPH

0 --H IGH > 15MPH

5 II 1111111 g t;;;;;;...;.=~r;o:;::o~----o.40--­

~0,~~-------.------~--o_.oo,~~-------.~--~--L-­-4 -2 1.0 15 2.0 6 7 8 910 12 14161820

STATIONS FROM NOSE GAP-SECONDS

TRAFFIC CHARACTERISTICS INDEPENDENCE AVENUE WESTBOUND ENTRANCE

EISENHOWER EXPRESSWAY, CHICAGO

Figure 69

92

RAMP

''S0,-------------=-;cl5;-:r--------.,

3=48

3=46 czo::::.

3:36 t======== 3=36

3'34 t-.~;r.v[Io;L~U~M:-':,:;::-E:-v:z;.;.;P.::-.;.;H".J::::::::-_1200 3=34

3=32+------,------~-----,---------l ·4 ·2

STATIONS FROM NOSE STATIONS FROM NOSE

120----

:--------....__ .--140=::::::.

---------------~120---------------~------===:::1~~===::::

''"OT----c--;:::::::=l~.o:--,::::=::::::"'i.75S.L:::::------~

:: ~:s. ~ --

jlno;oE;;;NS;;I;;:T:;;Y-=:c-vv.P.c.Mu.l"j----------40-----

60'-------3:38 ----125---- ~

15~

=--~ ,...--2.o_ 1.75

3:34

3=32 ·4 ·2

STATIONS FROM NOSE STATIONS FROM NOSE

3:50 5

[ 3:48

3:46

..... 3=44

" ~

0 I' II GAP ACCEPTANC~ I I CHARACTERISTICS f.----

----e--- I

----I

0

~ I

80

)-, 3:42

~ ~

1---1-- I 0

I

~ 3=40 I

0

"' ;:: I 3=38 0

I I

3:36 RELATIVE SPEED

3=34 10 1: LOW < 15 MPHl --HIGH> 15 MPH

I I ~

5 ·2 0.5 0.6 0.7 0.8 0.9 1.0 1.5 2.0 3.0 4.0 5D 6.0 7.0 80

STATIONS FROM NOSE GAP~SECONDS

TRAFFIC CHARACTERISTICS CHENE EDSEL

EASTBOUND ENTRANCE RAMP FORD EXPRESSWAY. DETROIT

Figure 66

89

STATIONS FROM NOSE

STATIONS FROM NOSE

STATIONS FROM NOSE

5•52-,----._,..-------------~=::------, 15~20,

5:50

....,5:46 ,;

"' --5=44

~ .. ~5=42

"' >= 5=40

-------~·-----~· ----20- ~ -..::::::::::2·- ~20 - 30~2·-----35~ ~2·------~~~20~ ____ _,. ______ _

~ 15 5•34+---------.;---'-'-"'-----.----L._.---------i -2

STATIONS FROM NOSE

5•52,----~::::::=======::;1~.25'-==:-----,

5:50

5:48

..... 5:46 ,;

5:40

5

0

0

0

0

w 7

~ 6

~ 5 0

... ;:; 4 0

~ ~ 3 0

0

I

5

=======1.25--1.50---

1.75--

~~ /7w~ ~/ ---.50:---Q :75 r.o

STATIONS FROM NOSE

GAP ACCEPTANCJ ! CHARACTERISTICS i

I -1-c-

----f.-----'

------- !

i i l RELATIVE SPEEU' -LOW,; 15MPH --HIGH> 15MPH

f !

0.5 0.6 0.7 0.8 09 1.0 1.5 20 3.0 4.0 5.0 6.0 7.0 8.0

GAP-SECONDS

TRAFFIC CHARACTERISTICS GRATIOT

EDSEL EASTBOUND ENTRANCE RAMP

FORD EXPRESSWAY, DETROIT

Figure 67

90

_.:33

5:31

5:29

-;5:27

"' ~ .._.5=25

~

5:33

5:31

5:29

;5=27

~

~5=25

-24~8 ----

~20~ '--~--= ~!!._ ~ '- ~1622:: = =:> 20 ~~6~ -28 '-

----24 ~

-20--------------~ ~ 0

5:23

~ 15 LLI5:23

" " 5•21 5=21

5:19 5=19

5:17 5=17

5'15 5:15 ·4 ·2 ·4 ·2

STATIONS FROM NOSE STATIONS FROM NOSE

5•33 ,----=:----------------------------,

-•o~ 5=33

--1.5

5=31 5=31

c-r:~g---...._

~ ~:::== ---------------~:=•o-------I00-120~

~140~

~40-~-----.-------- -120-1 DENSITY-V.P.M.f ~ -1oo----..,..,----

5=29

~ 5=25

5=21

5'29

e_~5----:5:27

" ~ 1.5 ___

~ 5'25 1.0----

~ 5=23

" " ·c 5•21

5=19

5=17 1.0 __

5:15 -l-----=--=--::.-:,-:::•'-'o~-=-===------~-----""12'-"o"'--~------i 5=15

·4

5•33

5•31

5:29

~5!27

~

)-, 5•25

<l 0 5=23 w

"' " 5'21

5:19

5:17

S:l5 ·4

·2 0 ·4 ·2 STATIONS FROM NOSE STATIONS FROM NOSE

5

vl7 0

11 GAP ACCEPTANCn- 1/ CHARACTERISTICS

I/ 0 v 0

0 /

0

17 0

/ 0

0 /

v I RELATIVE SPEED -LOWS 15MPH --HIGH> 15MPH

10

1/ 0.5 0.6 0.7 0.8 0.9 1.0 1.5 20 3.0 4.0 5.0 6.0 7.0 8.0

STATIONS FROM NOSE GAP-SECONDS

TRAFFIC CHARACTERISTICS BRUSH HOLLOW ROAD EAST BOUND ENTRANCE RAMP ON THE NORTHERN STATE PARKWAY, NEW YORK

Figure 64

87

5:31

5:29

5:27

"' 5:25 0:

~ 5:23

l5

"' 5:21

"' ;::

5:19

5:17

5:15

5:13 ·4

5:31

5:29

5:27

~ 5:25

"' "' ~ l5 !!!

5:21

;:: 5:19

5:17

5:15

STATIONS FROM NOSE

~:::2:> 12~ 1~0 ~120 -~100 ~0:::::> ~0

100

~120 ::--:"";o> c ---==--== -140 _,.-

~120 c;:-__/-~100"-----120

60~100 60

-60

[DENSITY-V.P.M.J_so-- Coo -2

STATIONS FROM NOSE

"'"!--------:=======::::::::::-------, c: ~ --========10 -

~·-----------------15

5:25

:> 5:17 ~·----5""j~l~sP~E~E=D~·=M-=P.~H-~l;:::=:=:::::::~~::======::::;'~==::::..--J :c:::::::z ......----20 ___ ,5_ "'" -4 -2

STATIONS FROM NOSE

5,31 -,-----------==~-----------,

5:27

0: i 5:23

~ 5:21

"' ;: 5:19

5:17

95

90

60

"' 10 i1 ~ 60

~ ~ 5 0

1-ffi 4

~

0-

~ 3 0

0

0

~75

\)5 :.so

STATIONS FROM NOSE

GAP ACCEPTANC~ I CHARACTERISTICS

1---f-f---~ ----RELATIVE SPEED

1: LOWS 15M PH -- HIGH > 15 MPH

~ ;

5 -2 0.5 0.6 0.7 0.8 0.9 1.0 1.5 20 30 4.0 5.0 6.0 7.0 8.0

STATIONS FROM NOSE GAP- SECONDS

TRAFFIC CHARACTERISTICS ROCKAWAY NORTHBOUND ENTRANCE RAMP

ON THE VAN WYCK EXPRESSWAY, NEW YORK

Figure 65

88

>i 5

~ l';

!

i 5

~ l';

~ ;::

-:i 5

~ iS

~

7:18

7:16 "-0 7:16

~ 7:14

7:12

7:10

STATIONS FROM NOSE

7:26 7:26

7:24

7:22

7:20

7:18

7:16

7:14

7:12

A

-----~ ,. ~0 __ <-~,. ~ ~

-------=:::130::::::- ---

~~ ~~~~~ -------·•o-

r.=~;;:;;;=====7o-=---------so------..._ 7'10 I DENSITY-V.P.M.! ........_,_

7:24

7:22

7:20

:i 5

~ 7·18

l'; 716

~ ;::

7:14

7:12

7:10

7•o•+------,-------,------.-----__J 7:0 -4 -2 -4

STATIONS FROM NOSE

7:26 5

7:24 0

7:22 0

7:20 0

0 7~8

0

7:16 i

\v 7:14 0

0.15

7:12 0

7:10 I

5

( -~·~~.~< ~ -~··----------·

~~·-----

~:~ -2

STATIONS FROM NOSE

STATIONS FROM NOSE

I

I

GAP ACCEPTANC~1 CHARACTERISTICS v ,L.-1.--

I v v /I I

........--- I i I ~ I

v v I

I I

I

I RELATIVE SPEED I -LOW :515MPH

I --HIGH> 15MPH I

I i ' i 7:08

-4 -2 0.5 0.6 0.7 0.8 0.9 1.0 2.0 30 1.5 4.0 5.0 6.0 7.0 8.0

STATIONS FROM NOSE GAP-SECONDS

TRAFFIC CHARACTERISTICS KOSTNER WESTBOUND ENTRANCE RAMP

EISENHOWER EXPRESSWAY, CHICAGO

Figure 70

93