You get a $50 traffic ticket on a road trip. You go home and send in the fine. Then, two months later, you get a notice in the mail that demands you cough up another $300 or lose your license and be subject to a criminal case. And because you paid that first traffic fine, you have essentially admitted guilt, so there's no way to escape or contend the new charges.
The Fast and Furious
Over past few years, some states have adopted what's loosely (and euphemistically) called Driver Responsibility laws, sometimes sold to the public as "bad driver" taxes since they kick in after drivers lose a certain number of points on their licenses. Using these laws, states can come back to you later and legally bill you for amounts that far exceed, usually by multiples, whatever you agreed to pay in court. It doesn't matter if you live in another state. And if you don't pay, that state can make it a crime for you to drive within its borders again. If you do, the case will no longer be civil--it will be criminal.
"Seems to me the low speeding fine was bait for a guilty plea so they could slap this on me a month or two down the road," complained one unnamed motorist to a driver advocacy website.