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Comment by btrettel | Hacker News Reader

How common are the issues you mention? I hear a lot more complaints from drivers having to pay legitimate sounding speeding tickets than I do bogus tickets. In fact, I can't think of a single instance of anyone I know who got a speeding ticket that wasn't legitimate. Corruption in the process of enforcing the law is not inevitable too.

I also am not comfortable calling the "85th percentile" rule a best practice. Seems like a moving target that has more to do with perceived safety than actual safety. Here's someone else's take: https://www.strongtowns.org/journal/2018/1/25/speed-kills-so...

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First of all, it's useful to distinguish two types of roads: those which are controlled-access exclusively for motorized vehicles, and those which are not.

Much of what you're trying to do is impose one-size-fits-all enforcement on both types. Controlled-access roads forbid pedestrians and bicycles, so arguments about protecting pedestrians and bicyclists on those roads fall flat. They should be using 85th-percentile metrics, in combination with the known design speed of the road, to set limits. But because controlled-access roads tend to have higher speeds, they're also the most tempting targets on which to run speed traps (i.e., if you can set a stretch of road to 25mph when the rest of it is 55mph, and park a hidden camera or cop right at the boundary, you can make a lot of money for your municipal budget, and precisely zero dollars of it will have been justified by increased "safety").

For the non-controlled-access roads, most of the real solutions the strongtowns/walkable/bikable/etc. movements want are going to come down to radically different infrastructure which have nothing whatsoever to do with speed limits. Speed limits are at best a non sequitur there.

I don't think you are responding to what I wrote. I never suggested a one-size-fits-all approach.

I don't think the 85th percentile rule is entirely bad, just not a "best practice", which sounds to me like "one-size-fits-all". The Strong Towns post I linked to said it makes sense for highways as I recall, which seems perfectly consistent with what you wrote.

Anyway, to reiterate, I am still interested in knowing how frequently speed cameras and the like are used poorly. The only uses of speed cameras that come to mind in my experience were not on "controlled-access" roads and seem justified to me. In fact, I rode my bike several times on one road with a speed camera that many drivers whined about back when I lived on the east coast. It was not uncommon for people to drive 15 mph or more over the speed limit there, despite the pedestrians. If I recall correctly the speed camera was added before a pedestrian crossing.

Edit: What I am recalling was actually multiple cameras on multiple roads. http://www.gazette.net/stories/12092010/laurnew185647_32536....

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