Serious snowmobile injuries are preventable and associated with late-night travel, alcohol use, and speed. We studied the effectiveness of a community-based policing (STOP) program in the prevention of serious injuries related to snowmobile trauma in Sudbury, Ontario. Volunteers were trained in police protocol and were appointed special constables to increase policing on snowmobile trails from 1993-95. Snowmobile admissions and deaths in Sudbury were examined; the pre- (1990-1992) and post- (1993-1995) STOP seasons were compared. In the pre-STOP period, 102 injuries, 87 admissions, and 15 deaths occurred compared to 57 injuries (p = 0.0004), 53 admissions (p = 0.00001) and 4 deaths (p = 0.13) in the post-STOP period. All other event and demographic features of the crashes remained similar. Significant economic savings were realized from this intervention; acute care costs savings exceeded $70,000/year and costs from death decreased by $5 million. An intervention involving enforcement on snowmobile trails can reduce the incidence of injuries from snowmobile-related trauma.