cross-posted from: https://sh.itjust.works/post/53463866
cross-posted from: https://sh.itjust.works/post/53463841
Before the cameras were installed four years ago, roughly 17 per cent of motorists followed the posted speed limits. … In the last year before the cameras were banned, compliance reached 87 per cent.
Within a week of the cameras’ removal, that fell to 62 per cent, and three weeks later, it had dropped to 50 per cent.
…
Carlucci says it’s time for drivers to reflect and consider one simple question.
“Why are you speeding in a school zone?”
Eliminating speed cameras is tacit approval of speeding.
The dirty secret of speed limits is that they’re often just the engineer’s best guess as to how fast the drivers who use the road will go, on average. Because they know that speed limits are useless for actual regulation.
Yup, they estimate the 80th percentile.
Basically, civil engineers estimate the top speed that 80% of drivers will be comfortable going on the road. And that estimated number is now the speed limit. That’s also the number they use to time traffic lights for ideal flow. That means 20% will naturally feel like it’s too slow, and will naturally end up speeding unless they constantly watch their speedometer. Because the number is estimated off of comfort, and 20% of drivers naturally feel comfortable going faster… And anyone below that 80th percentile will end up causing congestion as they crawl along below the limit and cause traffic lights to stop drivers who otherwise would have had a green.
And it’s worth noting that, in many cases, very little actual math or real world data goes into that estimation. It frequently boils down to a civil engineer basically going “well other streets like this one have a speed limit of 40, so 40 will probably work for this one too…” Civil engineering does have a lot of math for traffic, (for instance, turn lane length is determined by how many vehicles they expect to use it per hour,) but speed limits are often just a best-guess situation.