They are designed to operate on snow or ice, and do not require road or highway. Most snowmobiles are powered by a two-stroke engine, although four-stroke cycle engines are becoming more popular. A common cause of accidents is when a rider loses control of the machine because they do not have enough grip and they do not realize how powerful the machine is. Another cause of injury is clashing with large animals, such as deer and elk that venture into snowmobile trails. Most of these encounters occur at night in low visibility conditions, when the animal can not be seen in time to avoid a collision.
