The problem is implementation. My sat nav quite often thinks I’m on the wrong road, if I’m on a nearly parallel one, and its speed limit database is often outdated. I think perhaps it may work better on the more regular road layout of most US cities, however.
If your city’s roads are too small and tight for GPS-based speed limit detection to work reliably, there’s a simple and correct solution: a single, consistent, slow speed limit across the whole city. Voila, two speeding birds, one stone!
In practice that doesn’t work too well, though, because people rat-run through tiny residential streets, which is dangerous. Cambridge (on the UK) has a blanket 20mph limit across most roads citywide, but 30mph for specific primary routes, to funnel vehicular traffic on to the most suitable roads.
the thread started with the presumption that the speed limit would be actually enforced. But if rat racing is a still problem (people hacking their speed enforcement units?), speed bumps and road diets can still solve that.
Yes, if the limits are enforced then all roads are equal—so if someone can save 100 yards on a rat run, they will. If the rat runs are slower than the primary routes, there’s no incentive to use them—you don’t even need traffic calming, the difference in speed limit would do the job (if enforced).
Those tiny residential streets should have traffic diverters. 😏 They aren't even expensive!
It’s complicated. Cambridge does have a lot of traffic calming, and it’s closed off one end of many rat runs. But such measures are sometimes unpopular with residents themselves, as it can make harder to access their homes. There are also concerns around access by emergency vehicles. (1/2)
Cambridge also used rising bollards centrally, to allow buses and (sometimes) taxis, but not anyone else. They now seem to favour number plate cameras for this—there’s nothing to stop you ignoring the signs, but the registered owner gets a steep fine through their letterbox a few days later. (2/2)
I totally agree, my husband drives a F-150 Lightning, and its cruise control changes based on speed limit, but sometimes it is picking up a nearby road instead of the highway. But what I think we can/should do now is motion-based speed management. Like, turning tight turns, like on urban streets.