Surrogate Safety Analysis of Quebec Roundabout Design
Author(s): Paul St-Aubin, Nicolas Saunier, Luis Miranda-Moreno
Slidedeck Presentation:
Abstract:
Implementation of roundabouts has been relatively new in North America, and especially so in Quebec. As the original design of the roundabout originates from Europe, where a greater emphasis is placed on yielding behaviour and priority rules, some degree of uncertainty remains regarding suitability of certain design features of the roundabout in a North American context. This research aims to investigate the safety effects of various geometric design features, land uses, and traffic conditions on road safety of roundabouts in Quebec. Video data is collected at a large number of roundabouts across the major population centers of the province of Quebec. The video data is analysed automatically using computer vision to extract road user trajectories at various merging zones among the roundabouts sampled. Nearly sixty potential geometry, land use, and traffic factors are identified at each of these merging zones. Nearly forty merging zones are instrumented and annotated in this way. Smaller roundabout aprons were associated with higher speeds. Higher speed limits, were also associated with higher observed speeds, though only at a fraction of the posted increase. Irregular design of the merging zone, as well as presence of driveways on or immediately next to the merging 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, which in turn are also correlated with surrogate safety measures. There is strong interplay between these three components. In this research, a number of design factors are found to be associated with various traffic conditions and measures of surrogate safety.