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The hood (American English) or bonnet (British English) is the hinged cover over the engine of motor vehicles that allows access to the engine compartment (or trunk on rear-engine and some mid-engine vehicles) for maintenance and repair. In British terminology, hood refers to a fabric cover over the passenger compartment of the car (known as the 'top' in the US). In many motor vehicles built in the 1930s and 1940s, the resemblance to an actual hood or bonnet is clear when open and viewed head-on; in modern vehicles it continues to serve the same purpose but no longer resembles a head covering.
On passenger cars, a hood may be held down by a concealed latch. It is designed to protect a car from thefts, damage and sudden hood opening on the road. The hood release system is common on the most of vehicles and usually consists of interior hood latch handle, hood release cable and hood latch assembly. The hood latch handle is usually located below the steering wheel, beside the driver's seat or set into the door frame. When a driver pulls a hood latch handle the hood panel pops up and allows access to the engine compartment. On race cars or cars with aftermarket hoods (that do not use the factory latch system) the hood may be held down by hood pins. A hood may sometimes contain a hood ornament, hood scoop, power bulge, and/or wiper jets. Hoods are typically made out of steel, but aluminum is rapidly gaining popularity with auto companies. Aftermarket manufacturers may construct hoods out of fiberglass, carbon fiber, dry carbon, or polyurethane. Aftermarket hoods are usually sold unpainted or come primered in flat matte black paint. It means that such hoods require additional painting. To choose a paint that match vehicle's original shade and hue, special color code is used. This code is printed in the label that is usually located under the hood or on the driver side door jamb. Some car owners however prefer to leave their black primed hoods unpainted. Carbon fiber custom hoods require no painting, as they already come with protective clear coating.
In Japan and Europe, regulations have come into effect in recent years that place a limit on the severity of pedestrian head injury when struck by a motor vehicle. This is leading to more advanced hood designs, as evidenced by multicone hood inner panel designs as found on the Mazda RX-8 and other vehicles. Other changes are being made to use the hood as an active structure and push its surface several centimeters away from the hard motor components during a pedestrian crash. This may be achieved by mechanical (spring force) or pyrotechnic devices.