Roanoke Times
Copyright (c) 1995, Landmark Communications, Inc.
DATE: THURSDAY, December 1, 1994 TAG: 9412020018
SECTION: EXTRA PAGE: 8 EDITION: METRO
SOURCE: JOEL ACHENBACH
DATELINE: LENGTH: Medium
A: We are a nation of criminals. We routinely and blithely break the law. Even those of us who are not ``speeders'' in the classic sense are still fudgers.
If the speed limit is 30 mph we will routinely drive about 37 or 38 mph. Unless of course we see a police cruiser. Then we slam on the brakes so hard that the back of the car lifts in the air, and we drive past the cop at 15 mph with both hands firmly gripping the wheel, eyes concentrating on the road and checking left and right rearview mirrors at 0.5-second intervals, doing everything we can to project the image of Safe Driver, including signaling turns with arm signals in verification of the taillight blinkers.
Here is the tough intellectual question: Do we drive faster than the speed limit because the speed limit is set artificially low, or do we speed because we have an innate desire to get away with whatever we can get away with? If the speed limit on a typical city street were raised from 30 to 40 would we stop driving 38 and start driving 48?
The answer is: The speed limits are too low.
Most speed limits are set by a city council or county commission or state department of transportation. They cover entire jurisdictions - for example, a city might say that every city street has a maximum speed limit of 30 mph. But many of those streets can easily handle faster traffic.
Indeed, Julie Cirillo, acting director of the Office of Highway Safety of the Federal Highway Administration, says that most motorists drive at safe, rational, reasonable speeds, and that these speeds are not determined by the speed limit signs so much as by the nature of the street or road.
``Many, many speed limits are set legislatively, and therefore they have no relevance to anything, and they beg to be violated, and of course they are,'' Cirillo says.
Sometimes traffic engineers will study a given street to see what the best speed limit would be. They look at the cars flowing by. The general industry rule, Cirillo says, is to set the speed limit at the 85th percentile. What this means is that 85 out of 100 cars will be going at or below that speed. The other 15 percent will be going too fast.
Traffic engineers tend to be conservative, though. If they find that the 85th percentile is going at 49 miles an hour they will likely set the speed limit at 45. They round down. In fact, even when traffic engineers get involved, the average speed limit is around the 43rd percentile, Cirillo says.
We have obtained a graph from the Federal Highway Administration that clearly shows that on rural highways and freeways it is more dangerous to go a little bit too slow than to go a little bit too fast. For cars going 10 to 15 mph under the speed limit, the accident involvement rate is 449 accidents per 100,000 vehicle-miles. For cars going 10 to 15 mph over the speed limit, there are only 51 accidents per 100,000 vehicle miles. In fact, the safest speed appears to be 5 to 10 mph over the speed limit, with only 24 accidents per 100,000 vehicle-miles.
The reason is easy to understand: It's safest to go with the flow. Since speed limits are usually set artificially low, the safest and most efficient speed on a highway is right in that fudge zone of 7 or 8 mph over the posted speed limit.
We do not write this as an encouragement for people to speed. In fact the numbers show that going way too fast is extremely dangerous, more so than going way too slow. Cars going 25 to 30 mph over the speed limit have 7,072 accidents per 100,000 miles.
And these accident figures are for highways and freeways only. One should probably fudge less on a city street - particularly in the neighborhood where the Why staff lives, because there are millions of small children. There, we suggest you get out and push the car.
|n n| A recent reference to Rush Limbaugh in this column incensed many readers. In a discussion of bugs we said that insects have six legs, spiders eight and - here perhaps our wit was injudicious - Limbaugh 10.
A typical reaction came from Janice P., of Grosse Point Shores, Mich.: ``I do not expect this `innocent' informational, fact-based column to express any political sentiments nor the writer to abuse his `journalistic privilege' by using it in any manner he wishes and hiding behind `free speech' to broadcast uninformed, ignorant, unprofessional, slanderous remarks.''
Dear Janice: We take the abuse of journalistic privilege seriously. Indeed we believe that it requires practice, practice, practice. We apologize to Mr. Limbaugh and to the thousands of offspring he is carrying in his larval pouch.
Washington Post Writers Group
by CNB