DESIGN OF VEHICLE ACTUATED SIGNAL FOR A

MAJOR CORRIDOR IN CHENNAI USING SIMULATION

Authors

S.NITHYA R.NITHYANANTHAN D.SENTHURKUMAR K.GUNASEKARAN

Presented by,

R.NITHYANANTHAN S. KALAANIDHI

Introduction

Most of the cities in India have fixed time signal settings and it is operated manually during morning and evening peak hours.

Manual operation is adopted assuming that the traffic police personnel would judge the length of queue in each arm and would apportion green time for vehicles to clear the intersection based on queue length.

Manual control does not offer considerable benefits in reducing the delays of all vehicles.

Vehicle actuated (VA) equipped with Virtual Loop detectors and the necessary control logic to respond to the demand placed on traffic movements to be serviced.

Benefits of Vehicle Actuated Signals

• Handle the random fluctuations in the traffic condition

• Works on the real time information

• Vehicle presence is conveyed to the controller through the detectors placed for the various movements

• Reduce the overall delays and optimizes the signal timings at the intersection

• Especially effective at multiple phase intersections.

Need for Vehicle Actuated Signals

When demand varies

significantly from time to

time, either green time is

wasted or queue forms.

To avoids these variation

in arrival vehicle actuated

signal are necessary

Wasted green Queue forming

Vehicle actuated signals with varying phase time which

automatically varies the phase time helps in improving the

intersection function

Real Time Detection of Traffic

• Video cameras with virtual

loop detectors are able to

detect the presence of

vehicles.

• This virtual loop is used to

place at nearby intersection

and also for advance

detection.

• Multiple detection zones per

lane possible to cover a

larger area

Narrow Angle Wide Angle

ADVANCE DETECTION

STOP BAR DETECTION

Length of Detection Zone

depends on Permitted speed

Vehicle Actuated Signals

Actuated Control may be programmed to accommodate

• Variable Phase Sequence

• Variable Green time for each phases

• Variable cycle length, caused by variable green time

The cycle length, phase splits, even the phase sequence may vary from cycle to cycle.

Semi-actuated control

Detection only on minor side-street approaches; green remain on the main until a “call” for service on the side street is registered.

Full-actuated control All approaches have detectors; equal importance of the direction of traffic; for relatively isolated intersections;

Volume-density control

Basically functions like full-actuated control; good for high-speed approaches (>= 45 mph); Has extra features to adjust initial timing and reduce the gap extension during green extension time

Actuated control and controllers

Detection type

Point detection (“passage” type)

A single detector is placed for each approach lane to be actuated.

The detector relays information as to whether a vehicle has passed over the detector.

Area detection (“presence” type)

Generally used in conjunction with volume-density controllers.

The importance is placed on the existence of a vehicle (s) in the detection area.

They “count” the number of vehicles stored in the detection area.

Actuated control features and operation

Minimum green time

(Initial green + unit

extension)

Passage time interval

Maximum green time

Recall switch (unless

the subsequent phase

has the recall “on” green

remains to the previous

phase unless demand

exists)

Yellow and all red

Simulation Model Building

Model Building The processes and steps involved

Step 1 : Sections on the road network,

Step 2 : Vehicle types and classes were used to define the vehicle parameters.

Step 3 : Speed distributions defined from observed data.

Step 4 : Traffic compositions created for entry points to the network.

Step 5 : Placement of routing decision points in the network.

Step 6 : Placement of signal positions and signal timing in the road network.

Anna Salai, major arterial road in Chennai city, a stretch of 3.1 km was selected as

study stretch. With the development of educational institutions, commercial activities the

corridor have encountered problems such as traffic congestion, road accidents, and also

air pollution.

STUDY AREA

Intersection volume in vehicle/hour

S.No Intersection

Volume in

vehicles/hour

1 Thiruveka Junction 8883

2 Smith Road Junction 7086

3 Spencer Junction 12344

4 Wellington Plaza Junction 7881

5 Walajah Road Junction 11624

Video graphic survey at Spencer

intersection

Two video Cameras were installed on a tall building at Spencer

intersection to measure the volume and queue length in the morning from

7.00A.M to 12.00P.M

The survey was conducted during morning peak hour and evening peak hour.

The GPS instrument was used to measure the travel time and delay for the

entire stretch.

.

Travel Time along Study Corridor

•The travel time on Mount

Road from (Thiruveka junction

to Walajah junction) was

around 110 seconds in peak

hours and around 87 seconds

when travelling in opposite

direction

Study Stretch

Morning Peak Hour

(km/hr)

Thiruveka to LIC 24.504

LIC to Thiruveka 23.281

Travel Pattern in the Study Stretch The travel pattern has been arrived from the turning movements data. Totally 12

movements were considered. The in–out traffic is given in the form of O-D Matrix

1 1

2

3

4 5 6

8

7 9

10

11

12

OD projection for the study stretch

1 2 3 4 5 6 7 8 9 10 11 12 Total

1 - - 124 - - - 1784 - 710 948 - 948 4514

2 394 - 389 - 83 - 104 - 43 10 - 6 1029

3 - - - - - - - - - - - - 0

4 320 - 100 - 20 - 59 - 19 8 - 14 540

5 - - - - - - - - - - - - 0

6 188 - 40 - 12 - 228 - - - - - 468

7 926 - 342 - 64 - - - 190 240 - 456 2218

8 242 - 23 - 149 34 82 - 380 149 - 384 1443

9 - - - - - - - - - - - - 0

10 664 - 139 - 169 69 289 - 84 - - 2181 3595

11 742 - 84 - 174 - 149 - 24 1202 - 243 2618

12 1038 - 849 - 362 389 492 - 194 977 - - 4301

Total 4514 0 2090 0 1033 492 3187 0 1644 3534 0 4232 20726

The scenarios were formulated to study the performance of the

study stretch and to identify the best option.

Scenario1: Existing Condition with fixed time signal

Scenario 2: Vehicle actuated Programming

Scenario 3: Co ordinate fixed time signal

SCENARIO FORMULATION

Model Validation

The validated model was within the tolerance of the validation criteria (10%).

To validate the model correctly comparisons were made exiting volume with the observed volume

Ju

ncti

on

Street Vehicle Movement

Number of Vehicles / hour

Simulated Condition Existing Condition

Sp

en

cer J

un

cti

on

Gemini Road

Left 647 784

Through 2499 2517

Total 3146 3301

EA Road

Left 311 328

Right 246 249

Total 557 577

Benny Road

Left 276 295

Right 3186 3926

Total 3462 4221

LIC Road

Left 100 94

Through 4104 4207

Right 456 538

Total 4660 4839

Total 11825 12938

Scenario 1 gives the existing condition of study area. . Fixed time signal settings preferred for

morning peak hour was used.

Behavior of Scenario 1 – Existing Condition

Scenario 2 gives the corridor performance with vehicle actuated signals

Variable cycle time / variable phase timing model was attempted for the intersections.

Behavior of Scenario 2 – Vehicle Actuated Signal

Defining vehicle detection zone by placing the two detectors for each lane in each approach.

The detectors sensed the presence/absence of vehicles in between them.

Cond.,

Towards Gemini Detector Exit

Detector Entry

Towards LIC

Thiruveka

Junction

Function of VAP

The cycle time of critical intersection was adopted for all intersections and co – ordination for

movement of vehicles towards Parrys was attempted.

The offset timing for the signals assuming vehicle speed of 30km/hr was considered for co

ordination.

Behavior of Scenario 3 – co ordinate signal

Comparison of VA with fixed timings

RESULTS AND DISCUSSIONS

The individual intersection

performance shows significant

reduction in delay to about 28% if

vehicle actuated signals are

adopted.

The reduction in intersection

delay for scenario 2 was from

20% to 39% when compared

with scenario 1.

At the critical intersection i.e.,

Spencer intersection the delay

reduction was 39%.

Comparison of Fixed time signals with coordinated fixed timing signals

RESULTS AND DISCUSSIONS

The cycle time of the signals

was assumed to be 140seconds,

i.e., the cycle time required for

critical intersection.

The speed of the traffic flow

was assumed as 30kmph.

On Co-ordination of signals an

average 8% reduction in delay is

possible when compared to

scenario 1.

Similarly if Co-ordination of

Vehicle actuated signals is

attempted, reduction in delay

could be realised.

Vehicle actuated signals is proposed to replace the existing fixed

time signals.

With implementation of Vehicle actuated signals 28% delay

reduction is possible.

Further reduction is possible if a Co-ordination of Vehicle actuated

signal is attempted.

With the development in technology like Virtual loop Camera it is

possible to erect Vehicle actuated signals.

CONCLUSIONS

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