In the 1950s Edmonton constructed 12 two-lane roundabouts on major roadways in the City. Subsequently, 7 of these roundabouts were replaced with 5 of them being replaced in the 1979 to 1993 period primarily for capacity reasons. Since the early 1990s a number of planning and design guidelines for roundabouts have been prepared by various jurisdictions to provide state-of-the-art guidance on designing roundabouts that accommodate traffic flows in a safer manner. While these guidelines vary somewhat in the details of their guidance, this study concluded that the Edmonton roundabouts had geometry that would currently be at or beyond the range suggested by these guidelines for key elements such as Inscribed Circle Diameter, Circulatory Lane Width, Entry and Exit Radii and Entry Angle. This geometry likely contributed to the ability of the Edmonton roundabouts to accommodate traffic volumes at the upper end of the expected capacity despite having significant unbalanced peak directional flows and pedestrian crossing volumes, in some cases. It also possible that this geometry had an impact on the collision records for the Edmonton roundabouts, which tend to represent some of the higher collision locations in the City. For the covering abstract of this conference see ITRD number E211395.
Abstract