Road engines were developed as portable versions of static engines with the cylinders over the firebox. Originally they were frequently moved to where they were required by horses, later chain drive was introduced. Steering was achieved by horses at first, later by a steersman on the front of the engine before the modern arrangement with the steersman at the rear developed.

The Traction engines can be divided about seven types;

PORTABLE ENGINES
	These were the first type of portable steam engine. They were primarily used on and around Britain's farms to power threshing machinery and sawmills. With no self propulsion, they were hauled by horses and were still in use well into the 20th century.
AGRICULTURAL GENERAL PURPOSE ENGINES
	These self propelled machines were the most common type of steam engine to be seen in the countryside where they served as mobile power plant for threshing, tree pulling and other general duties on the farm although they were very seldom owned and operated by farmers, but most usually by contractors. Preference for the cheaper petrol-paraffin fueled tractor caused production of these engines to cease in the late 1930s but they continued in use into 1950s.
ROAD LOCOMOTIVES
	These powerful engines, usually larger than the traction engines used in agriculture, were designed for the haulage of heavy loads of up to 120 tons on the public roads. Fitted with gearing fro three speeds, they were sprung on both fron and rear axles and carried an additional water tank which was fitted under the boiler enabling greater distances to be covered between stops for water. Showmens' engines were of this type although they were highly decorated and adorned with brass fittings. As well as hauling the equipment of the fair between venues, they also provided the motive power for the attractions and electric power for lighting.
STEAM TRACTORS
	These were small road locomotives which, if they weighed less than five tons were operated by a one man. Although used for general road haulage they were used particularly by the timber trade. The Garrett 4CD was the most popular vehicle of this type.
ROAD or STEAM ROLLERS
	These are perhaps the best known of the steam traction engines and were still working into the 1960s, even being used on part of the M1 motorway. With a top speed of only twelve miles per hour, they often hauled a trailer in which the operator and his family would live and a water tank. The early road rollers tended to be very heavy with one being built which weighed thirty tons was built but experience showed that other factors apart from brute weight and engines of twelve to fifteen became favoured. The rollers became lighter with the introduction of tarmac with some weighing as little as 3 tons.
PLOUGHING ENGINES
	Invented by John Fowler, at about 22 tons each, these were the largest engines produced. Worked as a pair or set, one built to pull right and the other to pull left, they were referred to as right hand or left hand engines (although the positions were the reverse when they were working). The engines would run along the edges of the field with a cable slung between winches mounted under the boiler of each engine. A plough would be attached to the middle of the cable and dragged through the soil by the engines. Such a pair of engines could plough up to thirty acres in a day.
STEAM WAGONS OR LORRIES
	These developed in the early 19th century, originally as overtypes with the engine mounted over the boiler as in traction engines. With chain drive and four or six wheels, they achieved speeds of up to thirty miles per hour and the most popular were built by Foden of Cheshire. The undertype developed with a vertical boiler and the engine mounted under the chasis, as ina modern track. Equipped with pneumatic tyres, the later models speeds of up to sixty miles per hour.