People often assume that vapor lock is a major cause of vehicle stalling along roadways on hot summer days. To determine the causes of vehicle stalling, surveys were conducted last summer of stranded vehicles along an expressway and 2,200 motorists were phoned at random in the Miami, Florida area. Combined results from these surveys show that more than 95% of the stalls were related to mechanical and electrical problems, flat tires, overheating, accidents, and running out of gas. Fuel-related problems included contaminated fuel, engine flooding, and vapor lock. Vapor lock was the possible cause of only 2% of the stalls.