Data Collection

property ptared, 'ht' \ldC'O camera will allow nara robe collected stmultaneouslvon multiple approaches ,m.! for Ilml:iple movements on a single approach.

The manual method o! datu collccticn i~presented here and assumes no 5"c'(ialequipment i-, 11><'11It IS irrpon"lll 10understand tha: if sunultaneo.rs measure-menr of delays on nlllilipk "pp.oadles-{)r for multiple moves wllhin arlapproach is needed. II...n ""Jiliple ..h....rvers or a \ .deotaping device is necessary

L Visit the sill.' to det eruune the best observation pointsand tune for observations.As in all darn-gathering cfrc'l1<. Ih ... observer should ascertain the bes. urn-of day 10 collect Ih., ,1.11.1 U,uall}; a delay SHldy is associ.uvd wllh Ill,' peakhour fOT the intersection. fOl ,i particular a:lproaeh 10 <Intnrersecuon, or fora nearby major tralfk generaror ;\ turning-movement count. or snmla: Ir~f-fie volume infouuation. liMy be needed prior to executing the delav 'Iudy.

2. Collect and record the data.Before collecting the dora, the ,!naIY'1 must decide which Idne~ 01 Idll ....groups should be measured, Tho! IIC:"" rN'ollni.ll" lane groups as Ole groupof lam,', on an approach lrom which driven can complete Ih~ , arue moveduring the ~~JUC~i)(11ill phase. f'01 example, a IW(I-Iane approarl, ro alllruerserrtrm Ihal IM\ .1 ,!t'ctiC.ll."d left-rum lane and a combined throughand right-turn lone would IMY'; the delay eerenntned scpHraldy for eachlime. However, il two lane approa(h composed (If n cornhined I('fr·rlll" .indrhrou~ lane and d combmcd right-turn and through lane-s-all corurolledby a single phJsl~l\ eonstdered IU be a lane' g101l1)..ud would warrant "single d('lay dercrminauon fur lh .. enrt-c lane group once rhc .lII.,IY'I hasidcntifled all of the lane jlmlll" for all of theapproaches,delay lntormauonem be rollectctl for each

As an (,XdlllPIc, IWO lanes will be studied: J) a kfHum lane with a dedi·cared lett-turn phas ....urd 2) a combined lhrough and rtghHllnJ lillie. Bnrhlanes need nOI II<"on the same approach 10 111<'intersection, although cl.llilcollection i~easier II IhC'y .rre on the same approach.

Tht procedure lor cotlerrton of rhe: data is quill' simple. V~illf>a fifteen-second time interval, the number of vehicles stopped on rile laue group isrecorded. llMI is .• llIla recording fOl this PlU"PQS(,assumes Ih~1 rarh of the<lopped velncies has bceu stopped or delayed for fifteen seconds. Somevehicles will be coumed more than once if they are stO;.>vcd fur more Ihanone interval, nIb b dll.t.'plalJle.

24 veh iclc Delay Study

Data Analysis

strnulraneouslv using a one-minute recording interval, the l11J111be-)"ofvehicles using the lane group on rhe approach=-and whether they l)1US:

Stup or uot-h also recorded. Assumiug that all vehicles whic.'1IJ111~tstop isapproximately fiftv percent. the procedure should continue unri. a minimum of 350 vehicles are observed eurenng the iniersccrion via this lanegroup. The Iorm on page 27, or one n:' similar design, may hI' used 10 recordthe findings. Also, it !Daybe helpful to have two observers per lane or lanegroup, with nile cnllening the delay tnformarion ~11i1 0.1]1' collccung ihc vol-ume tnformation.

J. Check the data before leaving the field.The columns should be quickly sununed and the average dda)' computedbefore leaving the field. 'rnese computations ,\~11be checked later duringthe analysis phase but are computed here in order to check rhar the col-lected data is reasonable.

L Summarize field data.1'0 summarize the data, add each of r1,,' rotumns as W~~don .. on rhe exam-ple data collection fonn. This should be done as a preliminary in the field, ifpossible. so that any anomalies can be revealed. Be aware th~1 the suruma-tlon of vehicle delays and the toral volume may not coincide, since uiev aretwo entirely different data items. The delay data may reflect vehicles ~ha~were delayed more than one Interval. thus counted more 1J1an once,whereas the volume numbers rencet each vcbicle counted once and onlyonce.

2. Calculate total and average control delay.

Several catculauons are needed.Pust, the total dday observed is l·...k.ulaterl.Tins value is siruply tll.: number of delay 1ntC'I""315rnnlnplied by fifteen .. :c-onds. For the example. this is 154 x 15 = 2) J 0 vehtrle-seconds of dclaj,One vl"hirlr·<rcQnl1 of dl"lay is one vehicl .. delaved for nne second.

The total delav divided by the (oral number of vehicles delayed equals theaverag .. delay per stopped vehicle. Fnr the example data t:I11sis 2310/233 -9.9 second, per vehicle. This value inwcu:es how JOll!.1a vehicle is delayed ifit is .required LO stop on the approarh. It is Hut used to determine the Levelof scrvtce for the approach.

Tilt ~vnag" delay IJI.'I vehicle is computed by <lividing the total delay hy thetotal volume. geM procedure rnuluplies this \laJI1~h)' 0.9,0 compensate

Vehicle Delay Study 25

fur ~iillJVliut: error; A concctioa Iauor io, added TO arcoum fUI 1]1<, df<tci Drthe average oUIII,"'r of \('''ick~1)(OCCsseJper cycle, And. ,1dJU>(l1l~'rll' arcmade for accelerarlon and deceleration time The reader i, 1.. 1~1,,·,1 [01111'"HeM lor further explanauon of trns method,

A very dose ar'Hoxlllldti.1n 01 the values obtained by the HeM procedure iscalcu.ared h~ ,1;\';<I;I1!:IhC' [mal ~ro(,I)f~Jdelay by .he total volume and mul-lip:)'lOg the result by 1.3 Fur 'he example dara, rhl' l~ (2310;.109)(1 3) -7.3 seconds pel vehrcle. 'fhl~ is the value .,,"(.! w idenliCy I)", lnt) ofService enrnnnrcred hy rhe Iraffir.

Often, the percentage uf total volume delayed is computed to provideInsight tnro what pornon of the rraffic is roreed to .HOp ar rhe tnrerserrton.For Illt' example data. Ihl) i) 2331409 - 0.5701 57%,

3, Compare calculated delays to Highway CapacityManual Level of Service limits,

11u: Level uf Sl'Jvil': i> ,kll'uuiucd by rhe average ronrrol dd.l} per vehicle,using the Highwa) (dJ),l(irv Manual limits for each 1.4"C'lof SCT\IU' U)ingthe tollowing table, Ih(' example approach operating durlng Ih e ol)~~IVII

rton (>C'ri(l(1,11 , ,I ,l'wmh uf delay per vehicle I~ at Level-of-Service A.

-l. HeM Levels of Service

Ccutrol Delay ('cr Vehicle, sec

.; J 0.0

I 10 I 1020.0

201 (0)50

); I 1055.0

H,11080.0

I >80.0

onclusions.I 10 summarize what the siully has revealed andall of the intersertion's lane grOllp~ have been

hould be presented gr<tphically 1.0 1.,cllil;lIl' <Inraction. This rype of preseutarlou will irnrnedl-~ of rh .. intersection that ale SlJrf~ring, and iteer 10 determine it the signal is perforrn.in!! asned average of me average- cld.ty per vehicle ra noverall tcvel of SCIVicefor the lntersectlon. This

Level uf Service

A

II

cD

E

F

4, Summarize and draw C

At this point, il b irllpurliUl,,1Jo I it has not revealed. IIstudied, then the results ~uuderstandlng of Ih~ir uucately idcuLify rnose ponionwill allow the uaIlic enginintended. If desired. d \Vcla:)be computed to ldenn!), an

26 Vehicle Delay Study

Vehicle DelayData Collection Form

Approach. ___________ 01.15"1\"1,£: _

________ Date: Tillie p", iuu;

weather: _

Vehicles Delayed '~olun,esI

Delayed TQI~II inn- -I)I +JII -~5 +60 No Delay

I

I,I

:I

I

Tot.]

Vehicle DeJay Study 27

value means hu,e. however. since the panern allJ quality of I.ows are whatis of interest.

Srvernl questions should be addressed with the fi,]diJlg;. They include putare nOl limirert ro: •

• How does this inrersecrlon's performance compare :0 ,'CSI of the sys-tem's performance?

(an things improve ar rhi> localion.'

• Should [here be an ongoing delay study 1)( this Iocation as part of a"ptevenrivc uraintenancc" program?

The question or capacity of the Imersecuon is inrcnnonallv mnlttcd I'ro111the previous lisr I}r questions. Capacity (all be determined by measuring>~llJldliOIl Dow rates, as exp'alned elsewhere in [his manual. and it lowLevel ot Servire (au mdicatc II capacity ckfici.:I)I'Y, However; the observershould refrain from drawing conclustons l'egurlill!l t'ap.lily from ].cv(;(.of'-Service OhS('JValjOIl~,

Vehicle Dela.yStudy 29

Vehicle DelayDatil Collet tiun Form

ApproJch Miller.

OdIC: rep I 1. 20 Tim,' 1,<,; ... 1. 4:00 PM-

WCd,lIel ,$/(If''!.lfL- _

Vehicles Delayed voturnes

l'ime , IJ ~30 .,..43 +60 Ild",~c<l Nt) l)cldY Tut al

4:00 .2 3 4 1 14 23 37-

4:01 .5 3 2 .3 15 1614:02 4 4 J! 0 1.5 fO 254:0.5 0 2 2 5 15 6 2f4:04 7 0 0 I 0 7 19 264:05 1 2 .5 8 26 8 544:06 0 0 0 2 22 6 284:0r 6 8 5 0 .f0 .f .f24:08 0 .5 6 9 1.5 19 I 344:0<;1 0 0 I 5 12 fO 224:10 7 6 4 0 21 3 24-4:11 0 .5 .5 " 6 22 284:1.2 .5 0 1 2 2 15 Ir4:15 4 4 .f 6 58 f 1 494:14 0 0 0 1 .5 .21 26

5ttbIOI"J 37 40 33 44,,,,.1 I 1.54 233 1r6 409

30 Vehicle Delay Study