Speed Limits

Michigan Compiled Laws (MCL) 257.627 through 257.628 outline how speed limits are permitted to be set throughout the state. The law permits two methods to set a speed limit. First, we can use a method called the Vehicle Access Point (VAP) method. In this approach, we count the number of driveways along a ½ mile segment. If there are 60 or more driveways and intersections, we can set that speed at 25 mph. 

The VAP speed limits are further detailed below:

The second method we have to set speed limits is based on the 85th percentile speed of free-flow traffic. The 85th Percentile Speed is the speed that 85% of vehicles do not exceed. Another way of looking at this is that only 15% of vehicles go faster than this speed, and 85% go at or below this speed. The state believes that this helps to minimize crashes and promote a more uniform traffic flow along a corridor. Many professional traffic engineers also believe that using the 85th percentile speed to set speed limits is the safest way to set-top speed expectations.

If you are thinking of requesting a speed study along your road please keep these new rules in mind. Often when a speed study is performed the calculated 85th percentile speed can result in increases to that limit. It's a pleasant surprise when a lower limit is justified but this is a rare event. Remember that the city's hands are tied when it comes to flexibility. If we study a roadway we must come into compliance with the law. In fact, the law is written to allow MDOT or the Michigan State Police to actually step in and raise local speed limits if they believe that the community is not in compliance with the law.

Using these two criteria to set speed limits can often raise speed limits above resident expectations. Unfortunately, this is the law and we must use these regulations when updating speed limits in order to have enforceable limits. One common misconception to remember is that drivers are not always afforded a 10 mph buffer to exceed the posted speeds before getting a ticket. If you are traveling above the posted speed you are "speeding" and you could receive a ticket for any speed in excess of the limit.

The best advice we can provide to our residents is to slow down and plan extra time in their travels. Please pay attention to yellow advisory signs that might suggest a curve or limited sight distance. Also, enter roundabouts and intersections at safe speeds. And lookout for the increasing number of pedestrians we have along our busy corridors and near our schools. Thank you and drive safely!