New Michigan law reduces speed gap between cars and trucks

| 2/10/2006

Michigan Gov. Jennifer Granholm signed legislation Thursday, Feb. 9, reducing the speed gap between cars and trucks in the state.

The new law, previously HB5104, increases the 55 mph speed limit for large trucks to 60 mph on highways where the maximum limit for other vehicles is 70 mph.

The higher limit applies to vehicles with a gross weight of 10,000 pounds or more and truck-tractors with trailers.

Other motorists will continue to drive at the current 70 mph limit.

Rep. Bruce Caswell, R-Hillsdale, the bill’s sponsor, said he sought the change to bridge the gap between slower and faster drivers, making it safer for all vehicles on the road.

During discussion on the bill in the Legislature, advocates for reducing the speed gap said it would make roads safer by improving traffic flow and more closely resembling “85th percentile” speeds.

In testimony on the bill this past fall, James C. Walker, an automotive consultant, spoke of the importance of setting speed limits based on the 85th percentile rule – the speed at or below which 85 percent of drivers operate their vehicles.

“Recent (Michigan) State Police data shows the 85th percentile speed for heavy trucks is 64 mph. A higher limit will merely be closer to reality,” Walker said.

Walker also told lawmakers the closer that speed limits are to 85th percentile speeds, the smoother and safer the traffic flow tends to be.

“Reducing differential speeds is one key to this smoother and safer traffic flow,” Walker added. “No safety benefit accrues to setting posted speed limits below the 85th percentile … and no safety benefit accrues from differential speed limits for trucks versus cars.”

Todd Spencer, executive vice president for OOIDA, said he is encouraged to see new law to address safety problems resulting from a large speed gap.

“While we think a uniform speed limit clearly makes the most safety sense for speed limits, the measure signed by the governor moves us a little closer to that goal,” Spencer said.

The new speed limit for trucks takes effect in November.

– By Keith Goble, state legislative editor