Description taken from Arcade version of this game

18 Wheeler: American Pro Trucker puts you behind the wheel of a semi-truck with a couple tons of payload behind you. Your job is to get that shipment across country, driving thousands of miles through America's heartland. The only problem? You only have about two minutes to do so. To that end, each of the stages aren't realistic in their scale, as you'll find yourself crossing entire states and region in a number of seconds. You'll see a street sign for Washington DC, and then thirty seconds later you're in Florida. The weather outside also changes drastically. The game's four stages include a trip from New York to Key West, a jaunt from St. Petersburg to Dallas, a run from Dallas to Las Vegas, and the final trip from Las Vegas to L.A. In addition, there are several bonus stages where you can upgrade your horn, muffler and engine depending on how well you can park your truck.

You have a choice of four different truckers, each with different speed, vehicle and engine rankings. They all have their own distinct personalities, and the design and decoration of their trucks mimics their eccentricity. There is a fifth trucker named Lizardtail, but rather than being your pal, this guy's one mean hombre. He'll race you in each stage, hurling insults and doing whatever he can to run you off the road. Beat him and you get bonus money. ~ Jon Thompson, All Game Guide