Star Travel Bus
From the Super Mario Wiki
The Star Travel Bus is an obstacle found in Mario Kart: Double Dash!! It is found in only two courses: in Mushroom Bridge of the Flower Cup, and in Mushroom City of the Star Cup. They are found driving on the main streets, and not on shortcuts making it safer to travel on the shortcuts. The effect of hitting a Star Travel Bus has basically the same effect as hitting a banana, simply leading to a wipe-out.