The code to unlock these is below, translated by Neo Bomberman from a NeoGeoFreak mag. Extra Car Mode: Hold brake pedal at the vehicle select screen, and hit 1, 2, 3, 4. Depending on the class of car you want, Simple, Normal, Hard, or Very Hard, your car will change to the construction equipment.

A steamroller (or steam roller) is a form of road roller a type of heavy construction machinery used for levelling surfaces, such as roads or airfields that is powered by a steam engine. The levelling/flattening action is achieved through a combination of the size and weight of the vehicle and the rolls: the smooth wheels and the large cylinder or drum fitted in place of treaded road wheels. A steam powered steamroller The majority of steam rollers are outwardly similar to traction engines …