several easy ways of doing this, for a career with the US DOT go here
http://careers.dot.gov/js_apply.html
if you want to work for your state or any other state you need to go to the state employment office and ask them about applying to work for the Transportaion Dept. they will set you up.
If you want try a search on the web, go to google type in alabama transportion dept and see what happens if you live in alabama
Try google and type " how o become a DOT officer and get over a million results to surf through.
Asking on here is like looking for a tire that fits your car at a chocolate factory...
For what its worth, I talked with a few of them DOT folks, and the few I did were former truck drivers, had no education worth speaking of but went to training through the employment office and tested and then got a state job... college and being a police officer is all just optional...not a requirement