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: Km Daily Trips between two continents : ~ 1.3 M.

SIGNALIZATION in ISTANBUL

STARTING POINT A basic (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 ( ): …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 AMBER or NO RED+AMBER between RED to GREEN in ISTANBUL >>> LESS STARTING LOST TIME SUSPECT

PURPOSE OF THE STUDY To examine drivers' behavior when 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 drivers 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

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

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 % 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 CATEGORYBENEFITLOSS 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 NAREDUCTION 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 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 :( 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 Pehlivan References: Driver Behavior under the Green Signal Countdown Information. H Köll, M Bader and KW Axhausen,2002, Driver behavior during flashing green before amber: A comparative study. 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/ pdf.// MUTCD, 2009, FHWA, USA