Data, not politics, should determine speed limits

David Bernhardt, Maine Department of Transportation commissioner, in 2012.
Julia Bayly | BDN
David Bernhardt, Maine Department of Transportation commissioner, in 2012. Buy Photo
Posted March 24, 2013, at 10:07 a.m.

Maine’s transportation commissioner is qualified to decide whether and where speed limits on the state’s interstate highway system could be raised. Pending legislation, LD 654, sponsored by Rep. Justin Chenette, D-Saco, would make that possible.

The title of Chenette’s bill, “An Act to Raise the Speed Limit on Interstate 295,” misrepresents its intent. As Chenette emphasized during his March 15 testimony in presenting the bill to the Legislature’s Transportation Committee, passage of the bill would not automatically hike the speed limit to 75 miles per hour. It would authorize the transportation commissioner to consider doing so, based on the department’s engineering expertise and knowledge of the roadways’ conditions. An amendment, supported by Chenette, would extend the transportation commissioner’s authority to Maine’s entire interstate highway system.

A bill passed by the previous Legislature made it possible for the Maine Department of Transportation to increase the speed limit to 75 mph on Interstate 95 between Old Town and Houlton. As amended, LD 654 would replace a piecemeal political approach to setting speed limits with a systematic approach in which transportation professionals base decisions on study, analysis and geography. It would allow engineers familiar with the roads, rather than elected officials in Augusta or Washington, to determine maximum safe traveling speed on interstate highways throughout Maine.

Research indicates that higher speed limits don’t make highways more dangerous. A Wisconsin Traffic Operations and Safety Laboratory analysis of almost 20 traffic engineering studies of the relationship between speed limit changes and crashes found that only Iowa experienced a significant increase in highway crashes after raising its speed limit from 55 to 65 mph. New York’s total crash rate decreased after it increased its highway speed limit to 65 mph, and a five-year study by the Automobile Club of Southern California revealed that the state’s total crash rate did not rise after the speed limit did.

A Michigan State Police report titled “Establishing Safe and Realistic Speed Limits” concluded that motorists’ travel speeds don’t change appreciably when the speed limit increases, but the perception that higher speed limits make roads less safe “can actually enhance safety by causing users to reduce risk-taking behavior.”

A National Motorists Association study of driver behavior in 22 states buttresses the Michigan report’s conclusion that increased speed limits don’t cause motorists to drive faster, indicating that average speeds deviated by only 2 mph after limits changed. The NMA study did note that speeding violations decreased after limits increased.

In most states, transportation and public safety officials base speed limits on the “85th percentile speed,” which is the speed that 85 percent of vehicles travel at regardless of posted limits. A speed study included in the Michigan report revealed that the average travel speed increased 1.3 miles per hour on the same highway after authorities raised the speed limit from 55 mph to 70 mph. Regardless of the speed limit, motorists traveled at between 72 and 73 mph on that road, reinforcing the observation that a majority of drivers travel at speeds with which they are comfortable.

This national data on driver behavior will prove helpful to the Maine Department of Transportation if LD 654 passes, as we believe it should. However, the condition of Maine’s roads should be the determining factor, and the people responsible for maintaining those roads know best about setting safe travel speeds for them.

http://bangordailynews.com/2013/03/24/opinion/editorials/data-not-politics-should-determine-speed-limits/ printed on July 22, 2014