Event-Based Framework for Noncompliant Driver Behavior at Single-Lane Roundabouts

Abstract

Roundabouts are an emerging form of intersection control in the United States. The nature of roundabouts, requiring drivers to yield at entry, promotes a level of road user responsibility higher than that at inter sections with other types of control. This research addresses current roundabout modeling and analysis methods by focusing on the types of driver behavior that are not gap acceptance–based, do not follow the offside priority rule, are interactive between traffic streams, and have unique effects on roundabout performance. A new framework for describing priority-taking, priority-abstaining, and priority-surrendering behavior at roundabouts is presented; a reduction methodology for the extraction of these types of behavior from video is described. The findings suggest that these noncompliant driver behaviors are, prevalent, may significantly affect roundabout performance, and remain unaccounted for in current modeling approaches. Furthermore, the results indicate that frequency of priority-taking behavior remains constant, whereas priority-abstaining behavior diminishes with time since construction of a roundabout.

Utilization of Gaps at Single-Lane Roundabouts

“…The average gap utilization factor was also compared at roundabouts that had been in place for at least five years with those in place for less than five years. Previous studies have shown that at less than five years, there is a considerable amount of confusion regarding appropriate negotiation of roundabouts ( 17, 24 ). The results of the t -test indicate that roundabouts in place for five or more years have a statistically higher average gap utilization factor ( t = 9.59, d.f., = 365, p < 0.0001 ) with 0.544 and 0.419, respectively.…”

“…Previously obtained video data obtained by Belz et al and additionally collected data in North Pole, AK totaling 60 hours of observations were reduced to obtain vehicle headways in the circulatory roadway and the time associated with when a vehicle on the approach entered into the circulatory roadway (see Figure 2) ( 17 ). The videos were collected on one approach at each of six single-lane roundabouts in Alaska, Vermont, New Hampshire, Maine, and New York (see Table 1 and Figure 3).…”

“…Having a timestamp associated with each circulating vehicle (taken at Point A shown in Figure 2 a ), as well as the time a vehicle entered the roundabout allows for the accepted gap to be broken in a lead portion and a lag portion and thus define the nature of how that gap was utilized. In addition, each entering event was flagged if it resulted in a priority taking event so that a comparison could be made between those that directly impeded the circulating flow of traffic and those that did not ( 17 ).…”

“…This research builds on previous work that addressed types of drivers who deliberately ignored, or were unfamiliar with, intended yield-at-entry traffic rules at roundabouts (17,18). As a roundabout only has a finite amount of space in which to handle perturbations in traffic, the effective use of gaps (particularly at high circulating flows) is critical.…”

“…One may contend that a driver who enters into the leading end of gap (of an appropriate size) will not be of detriment to roundabout capacity, whereas a driver who enters into the lagging end of a gap (of the same size) is likely to cause a disruption to some degree. Furthermore, late entry into a usable gap may serve as a marker for certain types of driver behavior phenomena at roundabouts, such as priority sharing ( 21 ), limited priority mode ( 22 ), and priority taking ( 17, 23 ). To this end, the research presented here explores the concept of gap utilization and proposes its suitability for inclusion as a calibration parameter in gap-acceptance based methods.…”