A car seat is the seat used in automobiles. Most car seats are made from inexpensive but durable material in order to withstand prolonged use. The most common material is polyester. Bucket seat and bench seat A bucket seat is a separate seat with a contoured platform designed to accommodate one person, distinct from a bench seat that is a flat platform designed to seat up to three people. Individual bucket seats typically have rounded backs and may offer a variety of adjustments to fit different passengers. Folding seats Early touring cars featured folding auxiliary seats to offer additional passenger capacity. Some early automobiles were available with an exterior rumble seat that folded open into an upholstered seat for one or two passengers. Some vehicle models offer fold-down rear seats, to gain cargo space when they are not occupied by passengers. A fold-down front-passenger seat was a feature on the Chrysler PT Cruiser to fit longer items such as a ladder inside the vehicle. Ergonomics: lumbar and thigh support The lumbar is the region of the spine between the diaphragm and the pelvis; it supports the most weight and is the most flexible. The adjustable lumbar mechanisms in seats allow the user to change the seat back shape in this region, to make it more comfortable and include adjustable lumbar cushion. Some seats are long enough to support full thigh and follow back curves. Safety The National Traffic and Motor Vehicle Safety Act enacted by the U.S. in 1966 established standards of strength for automobile seats. These included requirements for proper anchorage and construction of automobile vehicle seat assemblies. The legal requirements in some jurisdictions for a child to sit up front is and they must weigh more than . Some studies have shown that drivers have an aversion towards carrying the full capacity number of passengers due to concerns over insufficient vision through the back window. An anti-submarine seat is a kind of seat that incorporates specially shaped panels in the forward edge of the seat cushion, reducing the tendency for the occupant to slide beneath the seatbelt in a severe frontal collision. Anti-submarine seating is a safety feature that may be more important for the front seats than the rear seats. A child safety seat or child restraint system is a restraint which is secured to the seat of an automobile equipped with safety harnesses or seat belts,