01628745

Component

One of the main factors contributing to crash occurrence at high-speed signalized intersections is the dilemma zone: an area in which drivers face uncertainty regarding whether to continue through an intersection or to stop at the presence of the yellow signal. Providing a sufficient yellow signal interval, extending the green signal time, and in advance warning systems (AWS) are some of the methods to reduce the uncertainty. AWS was originally used with the aim of providing adequate time for stopping in advance of intersections before the onset of the yellow signal. However, according to previous studies AWS causes vehicles to increase their approaching speed. In this study, researchers reexamine the dilemma zone boundaries in the presence of advance flashing yellow signs. By analyzing more than 1,870 hours of data for two different intersections and for different directions new boundaries for the dilemma zone are presented. Researchers found that dilemma zone boundaries (with the presence of AWS) are different at different sites and different directions at the same site. The 10% of the stopping vehicles is 2.6 and 1.1 (mean=1.85, Std=1.06, variance=1.12) for different directions for the Ridgeway site and 1.7 for East bound direction the Southgate site. 90% of the stopping vehicles also is 8.9 and 7.8 (mean=8.35, Std=0.78, variance=0.60), and 8.7 for different directions for the Ridgeway and the Southgate site, respectively. Moreover, upper dilemma zone boundaries were higher than previously reported upper boundaries in the literature. The much larger values of the dilemma zone boundaries is due to vehicles speeding up during the flashing yellow light signs before the onset of the yellow signal in order to escape the dilemma zone. Hence, researchers argue that intersection characteristics and drivers’ behavior should be taken into account in the design of traffic signals, rather than assuming a pre-defined value for the dilemma zone boundaries.

This paper was sponsored by TRB committee AHB50 Standing Committee on Traffic Control Devices. Alternate title: Dilemma Zone Boundaries in the Presence of Advance Warning Signs

01618707

17-05794

English

18p

2017

Transportation Research Board 96th Annual Meeting

Digital/other

Figures; Photos; References; Tables

Behavior; Dilemma zone; Drivers; Signalized intersections; Warning systems

High speed signalized intersections

Highways; Operations and Traffic Management; Safety and Human Factors

Transportation Research Board Annual Meeting 2017 Paper #17-05794

TRIS, TRB, ATRI

Dec 8 2016 12:19PM