Speed limit forum: Smart engineering is best way to ensure safe roadways for all users
Panelists discussed the merits of proposed changes in Michigan’s speed limit laws at Wednesday’s forum hosted at the Michigan Municipal League and moderated by Tim Fischer of Transportation for Michigan and the Michigan Environmental Council. Concerns about restricting methods of setting speed limits to the 85th percentile rule were expressed by several panelists, while consensus emerged that engineering and planning fixes are the best way to ensure safe and efficient roadways for all users.
Potential legislation being discussed would mandate that the 85th percentile method of setting speed limits is used more uniformly across Michigan (currently, many municipalities are setting limits in response to other factors such as pedestrian volumes on a roadway). The 85th percentile method sets the speed limit at the point which is exceeded by 15% of drivers. If 15% of vehicles in a 25 MPH posted zone were traveling faster than 30 MPH, the method would set the speed limit at 30 MPH. Setting limits based on this method relies on research that shows that car accidents are reduced when the 85th percentile is the posted speed limit, and that drivers respond more to roadway factors such as visibility distance than they do to the posted speed limit.
Legislation is expected to be introduced in the next few weeks.
The majority of panelists saw fault with passing rules that would require setting speed limits based on just one of many tools available to planners. Carolyn Grawi, Director of Advocacy and Education at the Ann Arbor Center for Independent Living said that while the 85th percentile tool makes sense for certain roadways, such as restricted-access highways, setting speed limits with the tool across the board ignores local contexts such as roads near school zones and neighborhoods. Grawi also opposed using the tool in residential areas based on the potential that actual speeds may “creep” up if posted speeds are raised. Even slight increases in vehicle speeds decrease survivorship from pedestrian and vehicle accidents and make it more difficult for individuals with disabilities, young children, and seniors to navigate roadways. Read more