Characterizing driver behavior in dilemma zones at signalized roundabouts. (May 2019)

• Record Type: Journal Article
• Authors: Najmi, Ahmad; Choupani, Abdoul-Ahad; Aghayan, Iman
• Is Part Of: Transportation research. Volume 63(2019)
• Page Start: 204
• Page End: 215
• Publication Date: 2019-05
• Subjects: Signalized roundabouts -- Dilemma zone -- Driver behavior factors -- All-red interval -- Time to collision; Automobile drivers -- Psychology -- Periodicals; Automobile driving -- Psychological aspects -- Periodicals; Transportation -- Psychological aspects -- Periodicals; 629.283019
• DOI: 10.1016/j.trf.2019.04.007
• Languages: English
• ISSNs: 1369-8478

Abstract

Highlights: The dilemma zone at roundabouts and driving factors that affect the stop/go decision was studied. The DZ is shorter and closer to stop-line, as compared to signalized intersections. Driver reaction time match to a large extent with the values mentioned by AASHTO and ITE. Acceleration and deceleration rates are not similar to those values proposed by AASHTO and ITE. Drivers drive more conservatively at roundabouts and are more willing to stop. 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.