Study can't yet tell whether higher speed limits cut wrecks
HOUMA, La. -- Raising speed limits in areas where they were routinely violated seems to have cut down on speeding, but it's too early to tell if it has affected the number of wrecks, officials say.
The changes on 12 Terrebonne Parish roads and highways and one in Lafourche Parish are part of a federal test program, so results could affect communities nationwide.
The South Central Planning and Development Commission is almost one year into the $250,000 Federal Highway Administration demonstration.
The 13 roads were chosen from among 93 throughout Terrebonne, Lafourche, Assumption, St. Charles, St. James and St. John the Baptist parishes.
Traffic engineers studied possible changes, based on the prevailing speed for most drivers. For instance, on one street with a 25-mph speed limit, 85 percent of the drivers were traveling 37 mph or less. Its speed limit was raised to 35 mph.
When the Terrebonne Parish Council approved the changes in February 2005, Councilwoman Teri Cavalier cast the only "nay" vote, calling the changes an accident waiting to happen.
Raising the speed limit didn't change drivers' habits, said Kevin Ghirardi, the commission's metropolitan planning organizer administrator for Houma-Thibodaux.
For example, on a stretch of Louisiana Highway 1 where the speed limit had been 50 mph, about 85 percent of drivers were at or below 56 mph both before and after it was changed to 55 mph. Drivers did not speed up to 60 or 65 mph, Ghirardi said.
Many people drive at a speed they consider safe and reasonable, rather than the posted limit, Ghirardi said. The "Rational Speed Limit" theory is that setting that accepted rate as the speed limit makes for fewer crashes, because most drivers are going about the same speed.
Martha Cazaubon, South Central Planning project manager, said collision figures are not yet available.
Part of the grant is paying law-enforcement overtime to patrol the roads where speeds were changed.