It's very common on many highways. For example, police watch I-95 in VA like a hawk, and mostly outside the big cities.
As soon as you drive into the state there's signs telling you they will get you.
I believe GP's point was not about "specific enforcement of traffic laws by police" but "law enforcement agencies who are specifically charged with traffic".
"law enforcement agencies who are specifically charged with traffic"
Are there really any that are? I didn't think that was common, even in cities. In fact, many cities are issuing guidance to not enforce basic traffic violations to prevent pretextual stops.