Successful speed cameras require fair speed limits

Here’s another great article written by Jack McKay that appeared at GreaterGreaterWashington.org. Beautifully written, this piece helps to explain the reality of speed limits and driving habits. Of course, nothing compares to the widely publicized guide that can be found on the Arizona DOT website. These guides explain that basically, people are safe drivers by nature and that everyone drives at a speed that is naturally comfortable and safe. This is why the 85th percentile speed is often the best speed limit for a given road.

Both ADOT and McKay explain how it’s not surprising that people drive above the posted speed limit on roads where the 85th percentile speed is significantly higher than the posted limit. Is it that a vast majority of the population has complete and utter disregard for traffic laws? No! Is everyone in such a huge hurry on the roads? No! People are simply driving at a natural and comfortable and SAFE speed:

Now, an example, namely Porter Street/Klingle Road between Cleveland Park and Mount Pleasant. This looks like a bit of interstate highway plunked down in the middle of the city, evidence of a long-forgotten plan to make Piney Branch Parkway into an inner-city crosstown highway. It’s a four-lane divided roadway, limited access, no residences, no businesses, no crosswalks, no cross traffic, and it’s no wonder that drivers speed up at this point, not because they’re crazy speedsters, but because the road is clearly built for higher speeds.

The 85th-percentile speed for this road is 41 mph, as indicated by the 2006 Speed Study Map. Hence, the speed limit should be 40 mph, or maybe, if we’re being conservative, 35 mph. But in actual fact, the posted limit is 30 mph, which is more than “slightly lower” than the 85th percentile. It comes as no surprise that the speed camera placed at this location has been a bountiful source of speeding tickets.

It’s no surprise that traffic engineering has played virtually no part in the decision to set the speed limits and in the decision for the best solution to the alleged speeding problem. According to the engineering guidelines here, the speed limit should be higher which would eliminate most of the technical law violations with no impact or even an improvement in safety. But instead, the city chooses to CASH IN on this engineering deficiency rather than correct it and truly do something to improve safety and respect the motorists who drive there.

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