The sheer size and weight of commercial trucks are one reason these accidents often have deadly consequences. While a fully-loaded 18-wheeler can weigh up to 80,000 lbs., the average passenger vehicle weighs only 4,000 lbs. Tractor-trailers are also considerably longer than passenger vehicles, need more room to maneuver, and are prone to jackknifing. They are taller with greater ground clearance, which can result in underride accidents with smaller vehicles. Trucks have a longer stopping distance (20% to 40% farther), making it impossible to come to a sudden stop.