Michigan bill would reduce speed gap

| 9/15/2005

If a Michigan state lawmaker gets his way, the speed gap between cars and trucks traveling freeways in the state would be reduced to 10 mph to more closely resemble “85th percentile” speeds.

Rep. Bruce Caswell, R-Hillsdale, has offered a bill that would allow vehicles with a gross weight of 10,000 pounds or more to travel up to 60 mph – up from 55 mph. Other motorists would continue to drive at the current 70 mph limit.

In testimony on the bill before the House Committee on Transportation Tuesday, Sept. 13, 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.”

For the sake of safety, Caswell agreed it’s imperative the existing speed gap between cars and trucks be minimized.

“What we’re seeing is that’s too large of a gap on divided highways. It’s creating some very unsafe situations,” Caswell said.

“When trucks pull out to pass other trucks and can only go 55, we are seeing a huge backup in traffic. We’re seeing a lot of problems in that regard, so what we are trying to do is narrow the top end and the bottom end. Get them closer together so traffic is moving more smoothly with a more uniform speed down the highway. It’s safer for everybody.”

Caswell said he would be open to reducing the speed gap even more, but it would be nearly impossible to pull off.

“Politically, I don’t think that’s doable,” he said. “I think 60 is the best we’re going to get. And that’s better than we’ve got. So that’s what we’re going to go after.”

Todd Spencer, executive vice president for the Owner-Operator Independent Drivers Association, said while the legislation attempts to reduce the speed gap, lawmakers are missing a greater opportunity to do away with split speeds.

“One of the main reasons highway safety has improved even as states nationwide increase speed limits is because higher speed limits tend to eliminate or minimize speed variances that are often key contributors to accidents,” Spencer said. “It makes sense now for lawmakers to use this legislation as an opportunity to once and for all establish uniform speed limits.”

Walker said any concerns by lawmakers that higher speed limits for trucks would be more dangerous are not based on the scientific traffic safety engineering research from the past 60 years.

He asked the panel to keep in mind that the fatality rate on freeways is five times lower than on other roads.

In addition, Spencer said it is important that Michigan truck drivers communicate to their elected officials that uniform speeds are safer for all drivers.

Caswell echoed Spencer’s call to truckers.

“Any help truckers could give would certainly be appreciated,” Caswell said.

The bill – HB5104 – is in the House Committee on Transportation.

– By Keith Goble, state legislative editor