Citation

Najmi A, Choupani AA, Aghayan I. Transp. Res. F Traffic Psychol. Behav. 2019; 63: 204-215.

Copyright

(Copyright © 2019, Elsevier Publishing)

DOI

10.1016/j.trf.2019.04.007

PMID

unavailable

Abstract

In some Asian countries, roundabouts were designed as a tool for landscape and urban planning in less-populated areas, which did not initially need traffic lights. However, as the urbanization grew, it was needed to signalize these roundabouts to prevent accidents. One of the main reasons for high accident rates at intersections is the dilemma that drivers face when the signal changes from green to yellow. The purpose of this paper is to study the dilemma zone (DZ) at roundabouts and driving factors that affect the stop or go decision. This paper determines the length of all-red interval for yellow light running (YLR) vehicles, using time to collision (TTC) and kinematic motion (KM) methods. TTC sets all-red interval so that the "last to go" vehicles have enough time to clear middle of the roundabout before conflicting vehicles reach the conflict point. KM method applies the kinematic motion equations to estimate the time required to clear the conflict point. The obtained results for three roundabouts in Mashhad, Iran demonstrate that the DZ is shorter and closer to stop-line, as compared to signalized intersections. Drivers drive more conservatively at roundabouts and are more willing to stop. Comparison of TTC and KM reveals that the central tendency and dispersion measures of all-red interval are larger in disaggregate KM method. Studying driving factors shows that driver perception-reaction time of drivers at roundabouts matches to a large extent with the values recommended by AASHTO and ITE. However, such consistency is not observed for acceleration and deceleration rates.

Language: en

Keywords

All-red interval; Dilemma zone; Driver behavior factors; Signalized roundabouts; Time to collision