sj-5112 at grade intersections

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SJ-5112

Perancangan Geometrik Jalan

Ir. Sri Hendarto, MSc.Ir. Sony S Wibowo. MT, PhD

Geometric Design of Urban RoadsIntersection and Interchange

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Bibliography

Leisch, J.P. and Mason, J.M., (2005), Freeways and

Interchange - Geometric Design Handbook, ITE

AASHTO, (2001), A Policy on Geometric Design of

Highways and Streets

Bina Marga (1992), Standard Specifications for

Geometric Design of Urban Roads

Bina Marga (1992), Tata Cara Perencanaan

Persimpangan Sebidang Jalan Perkotaan

Table of Content

Introduction

Simple Intersection Design

Channelization

Intersection and Traffic Control

Sight Distance at Intersections

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INTRODUCTION

Intersections (US English)

Junctions (UK English)

Types of maneuvers

At the at-grade intersection, there are four types

of possible conflict:

oDiverging

oMerging

oWeaving

o Crossing

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Types of maneuvers

Case of Indonesia (right-hand vehicle):

oDiverging, crossing, and merging for right turn

oDiverging and merging for left turn

The objective of intersection design will be to

develop an at-grade intersections which

managing these conflict properly and safely

Types of maneuvers

Multiple Mutual Right Left

Diverging*

* case of right-hand vehicle, e.g. Indonesia

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Types of manoeuvres

Multiple Mutual Right Left

Merging*

* case of right-hand vehicle, i.e. Indonesia

Types of maneuvers

Weaving

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Types of maneuvers

Opposed Direct-right Direct-left Skewed

Crossing*

* case of right-hand vehicle, e.g. Indonesia

Basic Intersection Forms

T

T-Skewed

Y

Offset Right

Offset Left

Offset Skewed

Cross

Cross Skewed

Multileg

Single Ramp

Channelization

Fully Channelized

Rotary

(Roundabout)

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Notes of Basic Intersection Forms

The angle of intersection should be designed to

have 90⁰ or near 90⁰ (70⁰ ~ 110⁰)

Multileg should be reduced if possible � not more

than four legs

Avoid offset intersection unless there is adequate

distance for weaving

o offset left is better than offset right

o vehicle having entered and travelled along the highways can make a non stop left turn to exit

Notes of Basic Intersection Forms

The benefit of 90⁰ or near 90⁰ angle of

intersection:

o Can reduce the size of conflict area

oMore favorable for drivers in the term of relative position and speed to approach

o Can reduce length of time to maneuver

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Conflict Areas at Intersections

Every at-grade intersection has conflict areas

One of the main objectives in intersection design is

to minimize conflicts from all maneuvers

The accident potential can be decreased by

reducing the size of conflict areas


Major conflict:

o head or near head on collisions occur

Minor conflict:

omerging type collisions

The 90⁰ T and Cross Intersection have the smallest

conflict areas (in comparison to cross skewed and

multileg)

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To Reduce the Conflict Areas

Channelized intersections

omarking

o islands

Auxiliary lanes

Separated intersection (interchange)

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Intersection with Reduced Conflict Areas

Intersection with Reduced Conflict Areas

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SIMPLE INTERSECTION DESIGNSIMPLE INTERSECTION DESIGNSIMPLE INTERSECTION DESIGNSIMPLE INTERSECTION DESIGN

Simple Open Throat

Provides minimum radii treatment

Carried out within the following conditions:

oAt the area of extensive road side development

o Low turning volume

o Low turning speed (25 km/h or less)

oAn intersection of minor road with a through highway

oWhere environmental sensitivities exist

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Simple Open Throat

T-Intersections

Simple Open Throat

CROSS-Intersections

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Simple Open Throat with Auxiliary Lanes

To be applied where speed are higher and

turning movements are sufficient numbers to

increase accident potential

To provide additional lanes and/or tapers for

through and turning movement

To be used for vehicles either entering or leaving

the through traffic

To have function as acceleration or deceleration

lanes and tapes


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CHANNELIZATIONCHANNELIZATIONCHANNELIZATIONCHANNELIZATION

Channelization

Factors considered in the channelization design:

oTraffic volume

o Speed

oType of roadways forming

At rural locations where high speeds are

prevalent and accidents are usually of a more

severe nature

In urban areas where speeds are lower but traffic

volumes are higher � to increase the intersection capacity

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Channelization, design concept

Separation of ConflictsTo separate conflicts caused by the overlapping of maneuver areas

Speed ControlTo control speed by bending and directing movement

Yield sign control or reduce speed differential prior merging and weaving


Merging at a Flat AngleTo control the angle of conflict and to reduce relative speed differentials in

merging, diverging, weaving and crossing

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Control of Paved Areas by Use of IslandsTo reduce the excessive pavement areas caused by skewed and flared intersection

The large areas of open pavement may confuse drivers


Refuge for Turning Vehicles and PedestriansTo protect and store turning and crossing vehicles by enabling them to slow down

To protect pedestrians by providing a safe refuge between traffic streams

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Control of Prohibited TurnsTo block prohibited movements by making it is impossible to do


Segregation of Traffic Movements

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Islands for Location of Traffic PolesTo locate and protect traffic control device such as signs, signals, etc

Speed Change Lanes

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Islands

Area between traffic lanes for control of vehicle

movements of for pedestrian refuge

They may be raised areas

o Raised island with mountable curbs

o In some cases with barrier curbs to protect pedestrians and poles

or may be marked out on the pavement

o Simply painted on the pavement surface

Islands

Raised islands outlined by curbs

o Can be applied universally

Islands delineated by pavement markings

oGenerally designed in urban or semi-urban areas

o Speeds are low and space is limited

Non-paved areas formed by pavement edges

oUsed mostly at rural intersections

Temporary islands

o bumper curbing or sand bags

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Islands, functional classes

Directional Islands

oUsed in conjunction with a separate left turn lane design

Divisional Islands

o Raised median islands

oTo separate traffic lanes by direction and or by speed

oTo protect vehicles entering the right turn lane

Refuge Islands

o Barrier type curbs

o Installed at or near cross-walk

Divisional Islands

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Refuge Islands

INTERSECTION AND TRAFFIC INTERSECTION AND TRAFFIC INTERSECTION AND TRAFFIC INTERSECTION AND TRAFFIC

CONTROLCONTROLCONTROLCONTROL

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A Hierarchy of Junction

Making connection between roads in the same service-function categoryParticular type of junction layout depend on:o Volume

• are there small enough to require control?• Are they too larger offer sufficient gaps for priority control?

• Are they too large be interrupted by traffic signal control?

o Speeds• Are they low enough to accept minimum control?• Are they high enough to make interruption of flow dangerous?

• Are they high enough to require strict of access?

Hierarchy of roads

Arterials (Type A – Primary)

o Should offer free flow (no interruption flow)

o Strict control access

o Requiring grade separation for through traffic lanes

o Relatively high-speed entry to, exit from, through lanes, and on turning ramps

o Safety at speed is the most important requirement

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Hierarchy of roads

Arterials (Type B – Secondary)

o Should be capable to carry large volume at moderately high speed

o Flow should not be interrupted

o Interruption is allowable at moderate volumes under traffic signal controls

o Should be grade separated

Hierarchy of roads

Collectors

oModerate to low volume and speed

o 2-way roads

o Could be regarded as major flow at priority junction

Local (access) Roads

oVery low volume and speed

oMust be treated as minor road at junction

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Roads connection

Hierarchy of RoadArterials –

PrimaryArterials –Secondary

Collectors Locals

Arterials – PrimaryFree flow

interchange

Partial

interchange- -

Arterials –Secondary

Fully

directional

interchange

Partial

interchange/

Traffic lights

Traffic lights -

Collectors - Priority control

Roundabout/

3 or 4 way

STOP

Priority

control

Locals - -Priority

control

3 or 4 way

STOP

At-grade Junction

Junction layouts can be described geometrically as of TT, YY, and XX form

Junctions with more than 4-legs should be

avoided

Control measures will be UNCONTROLLED,

PRIORITY, or SIGNAL applied to some or all legs

of the junctions

Priority can be major-minor road or equal

priority

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Some Notes in Design

All junctions should have some control measure to

aid drivers and increase safety and capacity

o Either partially controlled by Priority or fully controlled by Signal (Traffic Signals)

The angle of intersection between traffic should

be near right-angles

T-junctions are preferred to X-junction, where

there is little or no traffic control

Some Notes in Design… continue

X-junctions are preferred to T-junction for Signal control

Channelization can materially increase traffic

capacity

o Increasing both vehicular and pedestrian safety

oAn Islands can lead vehicles into ‘correct’ positions to undertake turning maneuvers, protect vehicles waiting to

turn and provide protected area to assist pedestrian

crossing

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Islands must be properly designed to suit the

requirements of the ‘design vehicle’

oThese vehicles can negotiate any movement without encroaching on any other traffic lane

Suitable sight distances must be provided and

kept free from obstructions


Must be a division into ‘major’ and ‘minor’ flow

and clear indication to road users of the priority

between traffic streams

Must be good inter-visibility between conflict

traffic flow

The geometrics should permit speed

harmonization between merging and diverging

Channelization should provide separate lanes for

each maneuver in junction area

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Design of Priority Junctions

It is most important that traffic approaching a

priority junction should receive sufficiently

advanced warning of presence of junction ahead

oWhether that approach is ‘give’ or ‘take’ priority

Various techniques are available

oMust give a clear and unambiguous message to drivers

On the major-road approaches, it must be

advantaged-warning signs

o Case of the straight-though line or carry the largest flow

Design of Priority Junctions…continue

Proper treatment of the minor-road approach is

more important

oAdvantaged-warning sign GIVE WAY (British) or ‘yield

sign’ (USA) or STOP lines to indicate the boundary

between major and minor roads

o Including a ‘splitter island’ and the GIVE WAY/STOP

line to prevent ‘cutting by right turning traffic and to

assist pedestrians crossing the mount of minor road

oThe island should be marked and visible at night

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SIGHT DISTANCE AT SIGHT DISTANCE AT SIGHT DISTANCE AT SIGHT DISTANCE AT

INTERSECTIONSINTERSECTIONSINTERSECTIONSINTERSECTIONS

Minimum Sight Triangle

The required sight distances depend upon the

approaches speed

o Speed on the main highway

o Speed on the side road

Four possible actions of driver:

oTo accelerate

o Continue at the present speed

o Slow down

o Stop

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Minimum Sight Distance, at right angles

Minimum Sight Distance, on skew

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Sight Distance for Departures, crossing

Sight Distance for Departures, right turn

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Sight Distance for Departures, left turn

Sight Distance

Required sight distances along intersection

approaches are determined by the type of traffic

control

oNo control

o Yield control

o Stop control

o Signal control

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Sight Distance, Indonesia RuleTata Cara Perencanaan Persimpangan Sebidang Jalan Perkotaan (No. 01/T/BNKT/1992)

Jarak Pandang Pendekat

oDihitung perdasarkan tinggi mata pengendara kepermukaan jalan� 1.5 meter

Kecepatan (km/jam) Jarak Pandang Pendekat (m)

40 30

50 40

60 55

70 70

80 95

Sight Distance, Indonesia RuleTata Cara Perencanaan Persimpangan Sebidang Jalan Perkotaan (No. 01/T/BNKT/1992)

Jarak Pandang Pendekat (JPP)

oTinggi mata pengendara 1.5 meter

Kec. (kpj)

JPP(m)

Koreksi Tanjakan (m) Koreksi Turunan (m)

4% 8% 12% 4% 8% 12%

40 30 - - - - - 5

50 40 - - 5 - 5 5

60 55 - 5 5 - 5 10

70 70 - 10 10 5 10 15

80 95 5 10 15 5 10 25

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Sight Distance, Indonesia Rule… continueTata Cara Perencanaan Persimpangan Sebidang Jalan Perkotaan (No. 01/T/BNKT/1992)

Jarak Pandang Masuk (JPS)

oUntuk membelok masuk pada jalan major

Jarak Pandang Aman di Persimpangan (JPAP)

oUntuk kendaraan di jalan major’menyebrang’

Kecepatan(km/jam)

Jarak Pandang Masuk(m)

Jarak Pandang Aman diPersipangan (m)

40 100 60

50 125 80

60 160 105

70 220 130

80 305 165

Sight Distance, Indonesia Rule… continueTata Cara Perencanaan Persimpangan Sebidang Jalan Perkotaan (No. 01/T/BNKT/1992)

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SELESAISELESAISELESAISELESAI

sj-5112 at grade intersections

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