Sport Utility Vehicles (SUVs) have existed since the 1930s but experienced explosive popularity during the mid-1990s. Built on a truck frame, SUVs harnesses utility attributes and powerful engine performance. One of the first popular SUVs in the United States was the Jeep originally conceived based on a demand for a four-wheel drive vehicle during World War II. SUVs are generally associated with toughness and stout on-road and off-road handling manners. Originally constructed as four-wheel drive vehicles intent to handle off-road trails, SUVs have increasingly become the vehicle of choice for luxury-minded drivers with products like the Range Rover and Cadillac Escalade. A highly popular body style in the 1990s, SUVs are easier to find in the used car market. Today, many buyers opt for crossover vehicles over SUVs desiring a more car-like ride and lower center of gravity. SUVs would still remain attractive to drivers wanting a full-fledged four-wheel drive system and/or a powerful towing performance. Popular with four-wheel drive systems, SUVs equipped with two-wheel drive (typically at the rear wheels) is a good choice for customers wanting to save money and fuel while not requiring peak off-road ability. Most new SUVs are classified as mid-sized or full-sized models. Better for maneuvering and generally easier on consuming fuel, mid-sized SUVs like the Jeep Grand Cherokee appear similar to crossover vehicles but often feature greater off-road and towing equipment. Full-sized SUVs in North America are derived from full-sized pickup trucks. With full-sized SUVs, buyers may be intrigued by seating for up to nine passengers and towing capacity that can easily haul a trailer or a small powerboat. Fuel economy of full-sized SUVs has traditionally been unfavorable but new engine management technology, as well as six-cylinder engines being introduced, has made 2014 models more reasonable.