Traffic and Speed: Interesting post from LA IST on a new push to put the brakes on LA's rising speed limits
Click here to link to LA IST article, “There’s A New Push to Put The Brakes on LA’s Rising Speed Limits”
Excerpt from introduction of Ryan Fonseca’s article:
Years of research, the rules of physics and common sense all point to an established fact about street safety: the faster people drive, the more dangerous and deadly our roads become.
Despite that fact, Los Angeles and other cities across California are regularly raising speed limits on their streets. They're doing that in order to enforce speeding laws in accordance with something called the 85th percentile rule, which roughly says if enough people are driving a certain speed, that should be the speed limit.
If that seems like a counterintuitive and incredibly flawed process to make streets safer, a broad coalition of public safety agencies, advocates and lawmakers across the state agrees. And now a new bill introduced in Sacramento aims to give cities more control over how they set and manage speed limits.
SPEED CREEP
Here's a more detailed hypothetical of how the 85th percentile rule works on public roadways: say the posted speed limit on a city street is 35 mph. In order for police to enforce that speed limit using radar or laser, the city has to conduct surveys every seven to 10 years to determine how fast people are driving on that street. If the results show that at least 85% of drivers are going at or below 38 mph in that 35 mph zone, the 85th percentile rule requires the city to round the speed limit to the nearest interval of five, meaning the new posted speed limit will be 40 mph.
Fast-forward to the next survey of that street seven to 10 years later (if the city has the money to conduct it); if at least 85% of drivers are clocked at or below 43 mph, the speed limit would go up again, to 45 mph.
That "speed creep," as the task force report calls it, has been happening on hundreds of miles of streets in L.A. and across California.
And decades of research shows that even a 5-mph difference in speed can make all the difference in driver's ability to hit the brakes and avoid hitting a person, cyclist or other motorist.
A human body struck by a vehicle going 35 mph had a 68% chance of survival, according to researchers. That survival rate plummets to 35% if the vehicle is going 40 mph.