The energy (damage) of a crash is proportional to the square of the speed. Therefore a crash at 80 units per hour has over 1 and a half times the amount of energy, and thus one and a half times the damage, as one at 65 units per hour.

If anything, American highways are wider and straighter than the Autobahn.

[flagged]

In my town you don't get a ticket unless you are going 10mph over, and this is on surface streets. They might be stricter in the 20mph school zones though.

In the places where it’s like that, enforcement is lax and you’ll never need a radar detector.

In the other places, it’s very simple to sit in the right lane and you won’t be going wildly slower than the rest of traffic. There are always trucks and governed vehicles on the road that are going the speed limit that you can swim through the stream with.

I used to be in the camp of defending the legality of radar detectors, and really I don’t think they need to be legal, but at the same time the only people buying them are dangerous assholes who treat public roads like their personal race track.

It takes at least one ticket to pay off the investment which means radar detector owners intend to be repeat offenders.

There was a rule at some point that the way to set a speed limit was to measure the speed of cars using that road, and set the limit so that 85% were under and 15% were over. I don't know how much this is actually used any more.

From a safety point of view the proper way to do it is to decide up front what speed limit you want on that road, and then design it so that drivers feel unsafe going over that speed. If you have to have a sign telling drivers to slow down, you designed the road wrong.