Analysis on Intersection Traffic Signal Locations Change and Characteristics of Dilemma Zone

교차로 신호기 위치 조정과 딜레마존 특성 분석

  • Lim, Sam Jin (Policy Center, Korea Railway Association) ;
  • Lee, Young-Ihn (Graduate School of Environmental Studies, Seoul National University) ;
  • Kim, Kyung Hee (Transport Facility Department, Bucheon City Hall)
  • Received : 2012.08.01
  • Accepted : 2013.01.07
  • Published : 2013.02.28


This paper reviews the characteristics of dilemma zone by analysing the influence exerted by actual location of intersection traffic signal on behaviour of drivers approaching signalized intersection in urban area. The analysis of approach speed was based upon a 'before and after' comparison, measured at three sites where the locations of traffic signals were changed. The study demonstrated that, when traffic signal changed to yellow, the scales of dilemma zone were narrowed in case of stopping cars by moving up the starting point of the dilemma zone due to lowered spot speed. On the other hand, in case of passing cars, the end points of dilemma zone were moved further out to the rear due to increased spot speed. Therefore, changing traffic signal locations could make an impact to increase intersection safety through reducing the scales of dilemma zone. This study also found that, in cases involving vehicles with similar approach speeds, spot speeds could be differentiated following the change of signal locations due to the fact that there can be greater differences in both braking point and deceleration rate. Thus, when considering the appropriate measuring of dilemma zone, 'spot speed' rather than 'approach speed' appeared to be more appropriate criterion.


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