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In Collegedale, Tennessee, a consultant recommended cutting the speed limit from 55 to 45 “because the crash is 246% higher than the state critical crash rate.”

One of the ways you spot a bogus excuse is asking “why not even slower?” More formally, the argument is called “reductio ad absurdum“.

The speed limit is supposed to be close to the actual speed of traffic, which is 70 according to the police chief who asked for the new limit. That had already been reduced 15 mph to yield the old speed limit. When there were still accidents they called for it to be reduced by 25 mph instead.

If that doesn’t work the same logic compels a reduction to a 35 mph speed limit. Then 25. Then… hope your 4WD has a low range.

The rules for speed zoning already say how much accident rate can influence the speed limit: 5 miles per hour total. A high rate of speed-related crashes could justify posting 65. Otherwise the limit should be 70, the maximum allowed by state law.

According to a comment on the story, the state DOT disagreed with the change. Like most eastern Departments of Transportation, Tennessee’s is comfortable with speed limits 10-15 mph too low. When the request is for a 25 mph reduction, most traffic engineers start to feel guilty.

Most engineers. Obviously the city hired an exception. You don’t win traffic consulting business without being willing to tell the customer “yes.”

Or as the consultant put it, the study was “responsive to our client’s needs.”

The opinions expressed in this post belong to the author and do not necessarily represent those of the National Motorists Association or the NMA Foundation. This content is for informational purposes and is not intended as legal advice. No representations are made regarding the accuracy of this post or the included links.

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