SURROGATE SAFETY STUDY OF CANADIAN ROUNDABOUT MERGE ZONES

摘要

Implementation of roundabouts has been relatively new in North America, and especially so inQuébec. As the original design of the roundabout originates from Europe, where by comparison agreater emphasis is placed on yielding behaviour and unsiganlised priority rules in intersection design,some degree of uncertainty remains regarding suitability of implementation of certain designfeatures of the roundabout in a North American driving context.This research aims to investigate the safety effects of various geometric design features, landuses, and traffic conditions on road safety of roundabouts in Québec. In order to achieve this,video data is collected at a large number of roundabouts across the major population centersof the province of Québec. The video data is analysed automatically using computer vision toextract road user trajectories at various merging zones among the roundabouts sampled. Severaldozen potential geometry, land use, and traffic factors are identified at each of these mergingzones and 35 merging zones are instrumented and annotated in this way. Safety at each of thesemerging zone is quantified using surrogate safety methods, a proactive approach to road safetywhich makes use of road user trajectories to model potential collision courses from ordinary roaduser behaviour. Basic surrogate safety measures used in this work include driving speed andyielding post-encroachment time, but the more sophisticated time-to-collision measure, modeledusing motion-pattern motion-prediction, is also included in this analysis.Smaller roundabout aprons were associated with higher speeds. Higher speed limits, were alsoassociated with higher observed speeds, though only at a fraction of the posted increase. Irregulardesign of the merging zone, as well as presence of driveways on or immediately next to themerging zone were associated with more serious conflicts (as measured by time-to-collision).Additionally, lane configuration and roundabout size were less significant than expected. Overall,geometric design and land use factors use are found to be correlated with traffic conditions, whichin turn are also correlated with surrogate safety measures. There is strong interplay between thesethree components.