Mud Drags (also known as mud racing, mud running and mud bogging) is an exciting (and messy) form of off-road motorsport popular throughout North America and growing in popularity in other countries. The goal of a mud drag is to drive a vehicle through a pit of mud as far and as fast as you can. Winners are determined by how far a distance traveled through the pit and in the case that several vehicles are able to travel the entire length, the fastest time to get through the pit. Typically, mud drag vehicles are four-wheel drives including pickup trucks or sport utility vehicles modified with lifted suspensions and larger tires. Engine upgrades and supercharges are also common. In the late 1970s and early 1980s, large tractor tires became popular, and the drive lines required to run such tires led to some of the first purpose-built mud drag vehicles. Today, many sanctioning bodies give precedence to vehicles with modified, and lower, dragster-type "rail designs" because of their popularity with mud drag fans.