I'm pretty sure this is one freedom US people won't let technology take away in the name of safety and ease of use. The roads and the culture are the problem. You can go fast and people will say going as fast as you can the whole time is the right way to drive.
It's bad road design. US roads are nearly all designed to encourage high speed travel by being mostly straight, perfectly smooth (well, until weather happens), and super wide. Then we slap a random-ass speed limit sign down and say "job's done." If roads were a bit less wide, even if just painted narrower, not dead fucking straight, and if you want to get fancy use something like how the Dutch use bricks for lower speed road surfaces, the road design alone would encourage lower speed driving.
Then we slap a random-ass speed limit sign down and say “job’s done.”
we don't actually--the basis we derive most speed limits from is actually much worse, if you can believe that. from Killed by a Traffic Engineer:
Traffic engineers use what we call the 85th percentile speed. The 85th percentile speed is whatever speed 85 percent of drivers are traveling slower than. If we have 100 drivers on the road and rank them in order from fastest to slowest, the 15th fastest driver would give us our 85th percentile speed.
Traffic engineers will then look 5 mph faster and 5 mph slower to see what percentage of drivers fall into different 10 mph ranges. According to David Solomon and his curves, the magnitude of the speed range doesn’t matter as long as we get as many drivers as possible into that 10 mph range.
and, as applied to the example of the Legacy Parkway, to show how this invariably spirals out of control:
North of Salt Lake City, the Legacy Parkway parallels Interstate 15 up to the Wasatch Weave interchange where these highways come together. It’s a four-lane, controlled-access highway with a wide, grassy median and more than its fair share of safety problems.
So how did the Utah Department of Transportation (UDOT) respond?
It increased the speed limit from 55 mph to 65 mph. It said the speed limit jump will “eliminate the safety risk” on the Legacy Parkway.
UDOT conducted speed studies up and down the Legacy Parkway. It found that most drivers were going much faster than the 55 mph speed limit. Channeling the ghost of traffic engineers past, the safety director for UDOT said, “We decided to raise the speed limit to a speed that is closer to what drivers are actually driving. In doing so, we hope to eliminate the safety risk of speed discrepancy, which can happen when you have a significant difference between the speed most drivers are actually traveling and those who are driving the posted speed limit.”
In the case of the Legacy Parkway, the 85th percentile speeds ranged from 65 mph to 75 mph. Based on that and what it deems engineering judgment, UDOT originally proposed raising the speed limit to 70 mph. After community pushback, it settled for 65 mph.
According to the Manual on Uniform Traffic Control Devices (MUTCD), this slight adjustment is acceptable. The MUTCD specifies that speed limits “should be within 5 mph of the 85th percentile speed of free-flowing traffic.”
Honestly, the 85 percentile rule, when actually used, is about the same as RNG, but with a bias for higher. Iforget where I saw it, but from what I remember seeing even the 85% rule gets deemed as too resource intensive so a speed limit from a "similar" (for some random definition of similar) road's speed limit is used.
I feel like it was something in the vein of a Strongtowns or Climate Town video.
Edit: Which now that I think about it, I'm reasonably sure the video also referenced the MUTCD.
Hope they keep those maps updated, the assist on our BMW constantly gets the speed limits wrong. There's a section that was changed from 50km/h to 70km/h years ago and it still gets confused because the signs don't match the map it's using, flip flopping between the two multiple times.
But at least it's just an option, it doesn't restrict or automatically do anything so it's not a huge issue.
BMW probably know this feature goes very underutilised by their target demographic so they hope nobody notices.
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