Signalization Safety and Driver Behavior Study with Flashing Green and Amber Time at Signalized Intersections in Istanbul

Authors:Ersoy Pehlivan, Sencer Oktav, Rahime Gunay

ISBAK Inc. Istanbul,Turkey

CONTENT

Starting Point

Signalization in Istanbul

Purpose of the Study

Methods & Research

Application

Conclusions

ISTANBUL in BRIEF

8th Largest city : 5.4 sqkm

Population (2010) : ~ 12,6 Million

Daily Trip : ~ 21 M. T

Total Vehicle : ~ 2,6 M.

Total Active Vehicle : 1,7-1,9 M.

Daily Addition : ~ 400 veh. /day

Total Road Network : 25.000 Km

Daily Trips between two continents : ~ 1.3 M.

SIGNALIZATION in ISTANBUL

Figure of Signalized Intersections (1950 points)

in Istanbul Metropolitan Area

STARTING POINT

A basic e-mail (tkm.ibb.gov.tr):“….Yellow time is too short in Red Light Enforcement System (2 sec.) I don't have enough time to stop my car. That is why, must be green flashing application at all junctions which are equipped with Enforcement System.”

Another phone call (44 44 154): “…When the green starting to flash should I ready to stop? or opposite; accelerate and pass the intersection? How the drivers will deal with this uncertainty? “

STARTING POINT

At the beginning,

there was a difference of opinion between the Metropolitan Municipality transportation department officials working on road safety, signalization and enforcement systems.

“…Flashing Green, is it a sufficient way to preventing violations? Or else the drivers will step on the gas?”

SIGNALIZATION in ISTANBUL

NO AMBERor

NO RED+AMBER

betweenRED to GREEN

in ISTANBUL

>>>LESS STARTING

LOST TIME

SUSPECT

PURPOSE OF THE STUDY

To examine drivers' behaviorwhen the signal is operated

with and without the flashing green application

as well as when the duration of the yellow change interval is extended

at signalized intersections in Istanbul Metropoliten Area.

METHODS & RESEARCH

We know that the approaching speed and distance to the intersection are the 2 most

important things that affect the driver’s behavior.

In addition,

The other studies showed the effects of the yellow change interval and flashing green on stopping time at the stop line when

the drivers proceed at a constant speed.

METHODS & RESEARCH

In Austria (since 1969) , same as Israel and Cuba:Green>Green Flashing>Amber>Red>Amber+Red>

In Spain: instead of flashing green: “Yellow+Green” is used together.

In Austria, Canada, Turkey, Mexico, Russia, Slovenia, Lithuania, Israel THE MESSAGE: “a flashing green light is used in intersections to indicate that signal is going to change from green to red soon.”

In USA, France, Italy, France, Belgium and some other EU countries Yellow+Red signal before the green was abandoned (same as Istanbul but not as other Turkish cities).

MUTCD 2009: Chapter 4D, item D of paragraph-3 states specifically, "A flashing green signal indication has no meaning and shall not be used."

METHODS & RESEARCH

The drivers in Austria tend to stop earlier. Some 3% stop already during the period covered by the flashing green and 70-80% by end of the amber (7-8 s period is included due to the one approach in Linz with a four second amber duration). In Germany & Switzerland only about half as large (28-35% during the 2-3 s

potential green interval). This response leads to a longer interval during which a following car driver

cannot be sure, how the car driver in front will decide.(H Köll, M Bader and KW Axhausen, 2002)

METHODS & RESEARCH

With Reference to Köll, Bader and Axhausen (2002):The flashing green in Austria

is associated with a substantial increase of early stops,

produces a large option zone, where drivers can both safely stop & pass.

the dilemma zone is minimised. This large option zone generates a period of uncertainty, where a driver following cannot easily predict, if the car in front will stop or cross.

the choice models highlighted higher speeds and lower distances to the stop line reduce the likelihood to stop.

No other variable had a significant impact which could be separated from the specific measurement locations.

METHODS & RESEARCH

AS a CONTINUING STUDY (to follow Köll, Bader and Axhausen): 8 signalized intersections on the main road (Kennedy Street)of the Eastern part of the Peninsula in Istanbul were chosen as test sites in both upstream (sectionB) and downstream (sectionA) directions according to the assigned scenarios.

3 scenarios are discussed:

METHODS & RESEARCH

METHODS & RESEARCH

METHODS & RESEARCH

APPLICATION PHASE

According to the resolution:

Implemented in 1860 signalized intersections in 3 weeks.

Flashing green was terminated and the duration of yellow change interval is extended to minimum 4 seconds.

Yellow change interval time was extended from a minimum of 2 seconds to 3 seconds.

Duration of the yellow change interval was increased from 3 seconds to 4 seconds where the "Red Light Enforcement" application was used.

APPLICATION PHASE

APPLICATION PHASE

Turkish version:

Eng. version:

Screen Savers

CONCLUSIONS-1

experimental field results have shown that;

NO NEGATIVE EFFECTS of TERMINATING the GREEN FLASH on CAPACITY of INTERSECTIONS

NO SIGNIFICANT DECREASE in nr of VEHICLES PASSING THROUGH DURING the GREEN PERIOD and CONVERSELY, INCREASE from 1-5 %.

CONCLUSIONS-2

experimental field results have shown that;

RED-LIGHT VIOLATIONS DECREASED from about 0.5-2% to about 0-0.7%.

VEHICLES PASSING DURING the YELLOW-CHANGE INTERVAL INCREASE from 0.5 to 2%

PROPORTIONALLY with the EXTENSION of the YELLOW CHANGE INTERVAL.

CONCLUSIONS

CATEGORY BENEFIT LOSS

SAFETY DECREASE a nr of RIGHT-ANGLE ACCIDENTS

DECREASE A NR of REAR-END ACCIDENTS (1)

CRASHING RESULTS DECREASE the ACCIDENTS with DEATH & INJURY NA

INTERSECTION CAPACITY UTILIZATION

NA REDUCTION USE of GREEN TIME (2)

DRIVER COMFORT INCREASE the DURING of DECISION-MAKING

DIFFICULTY of PREDICTION of FRONT DRIVER's STOP/PASS DECISION

DRIVER BEHAVIOUR INCREASE the PREPERATION TIME to STOP (good driver)

INCREASE APPROACHING SPEED(bad driver)

USE with ENFORCEMENT SYSTEM

DECREASE the VIOLATIONS INCREASE VIOLATIONS in OTHER INTERSECTIONS

(*1) A nr of rear-end accidents increases a nr of more dangerous right-angle accidents.(*2) Because of tendency to postpone.

CONCLUSIONS

No complaints (zero) has been reported.

A descriptive e-mail has been written out for the citizens who have a complained about this issue.

Discussed with the taxi drivers working near the study area. Positive feedbacks are noted about increasing of yellow time. They agreed that the benefits of green flashing are exaggerated.

Dissemination: Final Report was sent to the other transportation departments.

@

:(

TAXI

This study has been proven that the extension of the yellow time is much more effective on drivers than

the flashing green.

Thank You,Goshinsetsu Ni Arigatoo

Ersoy Pehlivanwww.isbak.com.tr

References:• “Driver Behavior under the Green Signal Countdown Information”.

http://ir.lib.ncku.edu.tw/bitstream/.pdf• “H Köll, M Bader and KW Axhausen ,2002, Driver behavior during flashing green before amber: A

comparative study”. http://ecollection.library.ethz.ch/eserv/eth:25449/eth-25449-01.pdf , Zurich, Swiss

• “Non-motorized Vehicle Drivers Behavior with Flashing Green and Green Countdown at Intersections: A Comparative Study”. //ftp.hsrc.unc.edu/pub/TRB2011/data/papers/11-4220.pdf.

• MUTCD, 2009, FHWA, USA