On the other hand, if the speed limit was set at 75mph, would that remain the common speed of traffic, or would the common speed increase with the limit?
Speed limits are 70MPH, 75MPH even 80MPH in some places in the US, apparently.[0] One could probably look at percentages of speeding tickets and reckless driving violations compared to states with lower limits and get some interesting results.
It would increase up to the point where people wouldn't feel comfortable driving faster.
There's a huge benefit to this: there would be less inconsistency between driving speeds. It is more dangerous when someone is going 85 and someone else is going 65 compared to 85 and 75.
The most dangerous is when one car is much faster than the others. There is little difference in terms of the chance of a crash if everyone is going 65 or everyone is going 75. The crash is more likely to be serious, but at least the people who are speeding are less likely to plow into someone when they're distracted.
