Car door

Most vehicle doors are secured closed to the vehicle body with latches which may be locked to prevent unauthorized access from the exterior. There are a variety of car door locking systems. Door locks may be manually, or automatically operated, and may be centrally or individually operated. Also, they may be operated by remote control, with the transmitter often integrated into the main vehicle access / ignition key.

Additionally, rear passenger doors are frequently fitted with child safety locks to prevent children from exiting the vehicle unless the door is opened from the exterior. These are also frequently used on police cars, to prevent suspect criminals from escaping whilst in police custody.

Vehicle door latches on practically all vehicles today are usually operated by use of a handle which requires the user to pull, lift, or tug - with some force towards themselves rather than push. There is a reason for this. As late as the 1970s, some vehicles used exposed push buttons to operate the door latch, such as certain Opel models. The unfortunate side effect of this design was that external objects which touched a vehicle during a spinout could trigger the latch; the door would pop open and eject the vehicle occupants. A death which occurred exactly that way led to the landmark legal case of Daly v. General Motors Corp., 20 Cal. 3d 725 (1978), in which the Supreme Court of California merged strict product liability with comparative fault, and thereby affirmed the right of General Motors to introduce evidence that decedent Kirk Daly flew out of his Opel not only because the door popped open, but because he was intoxicated and not wearing a seat belt.

Door switches are simple on/off mechanisms connected to the interior light (dome light), and may also be connected to a warning light, speaker or other device, to inform the driver when the door is not closed. The door light is standard equipment on all cars. In American cars from the 1950s-1990s, they had buzzers or "door dingers" that sounded, along with the check light, whenever any door is open.

Most vehicle doors have windows, and most of these may be opened to various extents. Most car door windows retract downwards into the body of the doors, and are opened either with a manual crank, or switchable electrical motor (electric car windows other than the driver's window can usually be controlled at both the door itself and centrally by an additional control at the driver's position). In the past, certain retracting windows were operated by direct (up or down) pressure, and were held in the up position by friction instead of by an internal lift mechanism.

Other cars, particularly older US-manufactured vans, have hinged windows with a folded lever mechanism to push and hold the window out from its closed position.

Vehicle doors often include brakes, or 'stays', that slow the door down just before it closes, and also prevent the door opening further than its design specification. The current trend is to have a three-stage door brake.

Door brakes exist because the doors on the first vehicles were heavy, so they had to be pushed hard to make them close. Soon after, automotive manufacturers managed to construct lighter doors, but users were used to closing doors with force so doors quickly became damaged. Door brakes were then introduced to slow down the door just before the door closed to prevent damage; these soon became standard.

A conventional door, also known as a regular door is hinged at the front-facing edge of the door, and so allows the door to swing outward from the body of the car. These doors are relatively safe, in that if they are opened during forward motion of the vehicle, the wind resistance will work against the opening door, and will effectively force its closure. The operation of a vehicle door entering, exiting, or standing out side an opened vehicle door is extremely dangerous particularly at night even when looking both ways. The issue is the vehicle door in most cases provides not visual warning to other vehicle drivers to allow accident avoidance of another vehicle driver to have the time to take avoidance measures. New advancements have been made to allow the viewing of the opened vehicle door at night with the addition of highly reflective tape applied to the lower interior edge of the vehicle door ( see US Patent No. 9,308,859 ). These new advancements allow the opened vehicle door to be seen even with a person blocking the prior art systems such as a reflector or a light by providing reflex reflectivity exceeding fifty percent of the vehicle door behind a person legs blocking the opened vehicle door at night.

A suicide door is hinged on its trailing edge. The term "suicide door" was coined due to the potential for the door to fly open when the latch was released while car was in motion.

Scissor doors rotate vertically upward and are hinged at or near the end of the windshield. They are used in Lamborghinis, Alfa Romeos, and other brands.

Butterfly doors are similar to scissor doors, but while scissor doors move up, butterfly doors also move outwards, which makes for easier entry/exit, and saves space.

Gull-wing doors are hinged on their uppermost edge, at the roof rather than the side. They are so named because, when opened, the doors evoke the image of a seagull opening its wings.

Sliding doors open by sliding horizontally or vertically, whereby the door is either mounted on, or suspended from a track. They are commonly used on the sides of minivans, leisure activity vehicles, light commercial vehicles, minibuses and some buses as this allows a large opening for equipment to be loaded and unloaded without obstructing access.

A canopy door sits on top of a car and lifts up in some way, to provide access for passengers. It is similar to an aircraft canopy. There are no set standards to canopies, so they can be hinged at the front, side or back - although hinging at the front is most common. Canopy doors are rarely used on production cars, but are frequently used on the 'closed' variants of Le Mans Prototype endurance race cars. They are also sometimes used on concept cars.

A disappearing door slides down and under the vehicle. This type makes the whole side of the passenger compartment open, and only leaves a threshold to step over to get in and out. Also called the Jatech rotary drop door, or disappearing car door. One example of a car with disappearing doors is the Lincoln Mark VIII concept car.