The sport of Tractor pulling is a branch of motor sport were old tractors are adapted with the addition of a larger engine to get more power. The sport involves driving the tractor down a course whilst pulling a "sledge", which ad a weight on that moves up the sledge as it goes down the course, increasing the load on the front sledge, thus increasing the drag. The idea being to see who can pull it the furthest before stalling or digging in. The competitions are dived into classes for differing sizes of tractor and powers, with weight limits imposed for the classes. The top machines can have jet engines fitted with others having multiple engines. The machines are fitted with roll bars, anti-flip wheels at the back, and emergency cut outs with some classes having safety screens or netting in