Right now, this is still state level stuff. If you have documentation that a truck is operating illegally, contact the state police in the state the truck is operating in/through. The numbers will be in your motor-carrier atlas (if you don't have one, get one) The state police have the job of enforcing DOT laws, so they're your first choice.
The other thing you need to do is get "the green book". It contains the DOT laws that regulate trucking. Get this so you know whether you have a leg to stand on, seeing that you want to make trouble for other drivers. I'll bet you can't get a driver into trouble just because he's a Russkie, as an example. You actually have to have code violations, and the green book tells you what the codes are.
The other thing you need to do is get "the green book". It contains the DOT laws that regulate trucking. Get this so you know whether you have a leg to stand on, seeing that you want to make trouble for other drivers. I'll bet you can't get a driver into trouble just because he's a Russkie, as an example. You actually have to have code violations, and the green book tells you what the codes are.