A snowmobile, also known as a motor sled, motor sledge, skimobile, snow scooter, Ski-Doo, or snowmachine, is a motorized vehicle designed for winter travel and recreation on snow. It is designed to be operated on snow and ice and does not require a road or trail, but most are driven on open terrain or trails. Snowmobiling is a sport that many people have taken on as a serious hobby.
Older snowmobiles could generally accommodate two people; however, most snowmobiles manufactured in the last 25 years have been designed to only accommodate one person. Snowmobiles built with the ability to accommodate two people are referred to as "2-up" snowmobiles or 'touring' models and make up an extremely small share of the market. Snowmobiles do not have any enclosures, except for a windshield, and their engines normally drive a continuous track at the rear. Skis at the front provide directional control.
Early snowmobiles used simple rubber tracks, but modern snowmobiles' tracks are usually made of a Kevlar composite construction. Originally, snowmobiles were powered by two-stroke gasoline internal combustion engines and since the mid-2000s four-stroke engines have also entered the market.
The second half of the 20th century saw the rise of recreational snowmobiling, whose riders are called snowmobilers or sledders. Recreational riding is known as snowcross/racing, trail riding, freestyle, boondocking, ditchbanging and grass drags. In the summertime snowmobilers can drag race on grass, asphalt strips, or even across water (see Snowmobile skipping). Snowmobiles are sometimes modified to compete in long-distance off-road races.