Credit for the first steam-powered road vehicle is given to Nicholas-Joseph Cugnot, a French military engineer. The French minister of war, the Duc de Choiseul, commissioned Cugnot to build a steam carriage capable of transporting large artillery pieces. Cugnot's response was to build a heavy three-wheeled vehicle that carried no reserves of fuel or water. Consequently, it was very limited in its use, although it did perform as a carriage by carrying four passengers in Paris in 1770. It moved at only a walking pace and was considered impractical because, after the pressure diminished, the copper steam tank had to be refilled with water and a fire had to be built under it to develop more steam.

Steam engines use the heat of combustion to boil water, converting it into steam vapor. By this action, its volume is expanded greatly, creating pressure. The resulting pressurized...