Vehicle suspension was originally invented during World War II to improve the speed and handling of tanks. This technology has since been adapted for most vehicles and continued to be redesigned and improved. Modern suspensions include hydraulic suspension, which is useful for off-road vehicles; air bag suspension, commonly found on buses and trucks; and ordinary spring suspension, which provides passengers with a comfortable ride. Suspension systems have greatly benefited vehicle drivers by improving stability, durability, and ride quality over time.