It has increasingly become more common for speed limits to be set for political reasons rather than for safety reasons. But local officials that try to manipulate driving behavior by setting speed limits artificially low may be encouraging drivers to disregard speed limits altogether, a U.S. researcher reported on this week.
More than 1/3rd of the 988 people surveyed believed it was safe to drive 20 mph over the posted speed limit, and 43 percent thought it was safe to drive up to 10 mph over, said Fred Mannering of the Department of Civil Engineering and Economics and Indiana’s Purdue University.
Mannering attributes this lack of respect for speed limits to the 1974 Emergency Highway Energy Conservation Act that set speed limits to 55 mph on all interstate highways, even though those roads are designed for 70 mile an hour speeds. “Once you start going down the road of posting speed limits below where they should be, then there’s a general disrespect,” Mannering said. “Now I think a lot of people set the speed limits saying, ‘It’s safe to go 45 — let’s set the speed limit at 35′”
The term speed limit isn’t completely accurate anymore. Before 1974, speed limits were generally set at the 85th percentile, meaning 85 percent of the cars should be traveling at or below the limit. That way, you could get a good idea of how fast the cars on a particular stretch of road would be going. Now speed ‘limits’ aren’t limits at all, and are subject to the whims of any local official who wants to factor in noise pollution, fuel economies, pedestrian safety, or whatever.
Mannering thinks there are safer ways of encouraging fuel efficiency than setting speed limits at 55 mph, such as raising fuel prices. “If you want to save fuel — and I’m wearing my economics hat — do it with price.” Of course no one wants to hear that.