... " Michael D. Makowsky, a doctoral student in economics, and Thomas Stratmann, an economics professor, both at George Mason University, studied the issue in a recent paper, ''Political Economy at Any Speed: What Determines Traffic Citations?''
They examined every warning and citation written by police officers in all of Massachusetts, excluding Boston, during a two-month period in 2001 -- over 60,000 in all. Their conclusion wasn't shocking to an economist: money matters, even in traffic violations. They found a statistical link between a town's finances and the likelihood that its police officers would issue a speeding ticket. The details are a little sticky, but they show that tickets were issued more often in places that were short on cash, and that out-of-towners received tickets more often than drivers with local addresses." ...
(original paper by Makowsky and Stratmann available here)
So this paper provides some more evidence of tax exporting in transportation finance, a favorite topic of mine since my dissertation "On Whom The Toll Falls", extended in the book Financing Transportation Networks
More importantly, it is one less paper I have to write, it has on been my 'to do' list since my dissertation, but I never had the time to get together the data.
One could extend this work by looking at the location of "speed traps", where the hypothesis would be these are at the edge of town, and thus more likely to nab out-of-town drivers than in the middle of town (assuming imports=exports, and no through trips, 50% of all travelers at the edge of town are from out-of-town, a smaller percentage of travelers inside town are out-of-town; if there are through trips, then more than 50% of travelers at the edge are non-resident, while again a smaller number of internal trips are non-resident).