Mario was the hero in the mushroom kingdom that brought peace to all the lands. That was a long time ago and Mario can't leave being just a hero as he needed a job. Mario bought a truck since then and he makes money from delivering anything that was ordered. A mysterious guy ordered some mushrooms and now, Mario needs to fulfill this order. The mushrooms are scattered throughout the land, but Mario can't reach it if he would not use some sort of transportation. That is how he makes a living these days, but it doesn't mean that it won't be as challenging as before since the mushrooms are located in extreme land.
The goal is to get to the destination as fast as you can, but that won't be easy, especially that the land is a problem itself. There are no enemies that are going to harass you while you drive, but the condition of the land itself is pretty dangerous. There are lots of mountains and hills that would prove dangerous to your trip. One mistake and you are finish. You need to be careful all the time. The game gets harder and harder as you make some progress.