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Enforcing speed when the intent is public safety rather than revenue generation requires more nuance than what the current system in the US has to offer. Does

Enforcing speed when the intent is public safety rather than revenue generation requires more nuance than what the current system in the US has to offer. Does it make sense to strictly enforce a 20 or 25 mph limit in areas with residential/pedestrian traffic? Certainly, especially given that pedestrians crossing a street are essentially at a 25 mph speed difference relative to perpendicular traffic. But if we apply this arithmetic to semi trailers traveling at 65 mph on the highway, a 25 mph difference would suggest a speed limit of 90 mph, even neglecting the safety difference in a vehicle-vehicle collision. Where are most current speeding tickets issued? Is it in low-speed, residential areas where drivers know that an extra 5 mph won't save them any time at all (and would greatly increase the risk of injury in an accident)? Or is it in high-speed straights on the highway where an extra 15 mph can save you hours on long trips (where a speed limit effectively grandfathered from the malaise era still applies)? Another consideration: if speed enforcement on highways was so critical to public safety, why are radar detectors and even laser jammers legal in many US jurisdictions? My perception is that physics-based policy decisions never get far in the US system. Ultimately, automated enforcement/better technology seems orthogonal to the policy problem. We should get the policy right first.

imgabe 8y ago
> Is it in low-speed, residential areas where drivers know that an extra 5 mph won't save them any time at all (and would greatly increase the risk of injury in an accident)? Based on my personal experience in such areas, drivers very much do not know this. The number of people speeding down residential streets in my city just to get to a red light at the end of a block is astonishing.
- Chris_Chambers 8y ago
  What city?
fyfy18 8y ago
For a comparison, the other week I drove 4000km across Europe and most of the speed cameras I came across were in areas where the speed actually makes a difference i.e. in towns and residential areas. Along a three lane motorway it doesn’t make much difference whether you go at 130kmh or 160kmh, if you aren’t paying attention and do something stupid it’s going to end badly either way. From seeing where speed was actually enforced, it seems that the authorities here believe that too.
- hoppelhase 8y ago
  In Germany, speed cameras are placed where accidents are likely to occur when the speed limit is exceeded.
maxerickson 8y ago
Truck speed limits are lower than other vehicles exactly because of physics. Your suggestion that the speed difference is the thing that should be consistent across scenarios doesn't account for physics though. Kinetic energy goes with the square of speed, so the thing to look at is stopping distance from a given speed.
jacquesm 8y ago
Most speeding in residential areas (both in frequency and in delta relative to the limit) is done by the people that live there. There was quite a bit of research done regarding this and one of the conclusions that stood out for me was that the familiarity with the territory was a big factor in this.
upofadown 8y ago
There is nothing in the article suggesting that the license plate readers in the signs would be used for speed enforcement. The big problem here is that the cameras are intended to be secret. Openly using license plate readers for actual speed enforcement raises much less serious issues as there are politically enforced limits on what the data can be used for.

imgabe 8y ago

> Is it in low-speed, residential areas where drivers know that an extra 5 mph won't save them any time at all (and would greatly increase the risk of injury in an accident)? Based on my personal experience in such areas, drivers very much do not know this. The number of people speeding down residential streets in my city just to get to a red light at the end of a block is astonishing.

Chris_Chambers 8y ago
What city?

fyfy18 8y ago

For a comparison, the other week I drove 4000km across Europe and most of the speed cameras I came across were in areas where the speed actually makes a difference i.e. in towns and residential areas. Along a three lane motorway it doesn’t make much difference whether you go at 130kmh or 160kmh, if you aren’t paying attention and do something stupid it’s going to end badly either way. From seeing where speed was actually enforced, it seems that the authorities here believe that too.

hoppelhase 8y ago
In Germany, speed cameras are placed where accidents are likely to occur when the speed limit is exceeded.

maxerickson 8y ago

Truck speed limits are lower than other vehicles exactly because of physics. Your suggestion that the speed difference is the thing that should be consistent across scenarios doesn't account for physics though. Kinetic energy goes with the square of speed, so the thing to look at is stopping distance from a given speed.

jacquesm 8y ago

Most speeding in residential areas (both in frequency and in delta relative to the limit) is done by the people that live there. There was quite a bit of research done regarding this and one of the conclusions that stood out for me was that the familiarity with the territory was a big factor in this.

upofadown 8y ago

There is nothing in the article suggesting that the license plate readers in the signs would be used for speed enforcement. The big problem here is that the cameras are intended to be secret. Openly using license plate readers for actual speed enforcement raises much less serious issues as there are politically enforced limits on what the data can be used for.