[privong]

> I've often wondered why police don't do more of this.

Wikipedia claims[0] that this is not allows in California, though the citation has suffered link-rot.

I think enforcing speeding limits could also discourage the use of things such as ez-pass, which may very well result in more revenue, compared to the same tolls collected in cash by real people. So it could hurt the revenue stream from tolls.

[0] https://en.wikipedia.org/wiki/Speed_limit_enforcement#Averag...