Performance evaluations of the spiral-marking roundabouts in Hong Kong

The Hong Kong Transport Department initiated a trial of the spiral-marking system on four roundabouts in different phases between January 2004 and August 2008. In this study, observational and questionnaire surveys were conducted to assess how the proposed roundabout marking system affected driver behavior, level of service, and safety performance. The vehicle travel time, number of conflicts, crash incidence, and weaving movements were assessed before and after the implementation in the observation surveys, and the perceived safety, congestion level, and lane-changing difficulties were assessed through questionnaire surveys, respectively. Generally, drivers preferred the spiral-marking roundabout to conventional roundabouts, especially after trialing the new marking system. Inexperienced drivers, in particular, appreciated the spiral-marking system because of the increased safety level, reduced congestion level, and increased ease of navigation. On the other hand, the results of the observational survey indicated that there was no unfavorable change in the average approach lane choice, circulating time, and lane-crossing rate following the implementation of the spiral-marking roundabouts. The confounding effects of possible factors, including circulating lane width, entry and exit width, entry and exit curvature, entry angle, time period, and roundabout flow were taken into account in the multiple regression model. Nonetheless, there were marginal decreases in potential conflicts, with no significant reduction in crash frequency at the spiral-marking roundabouts.