The trunk or boot of an automobile or car is the vehicle's main storage, luggage, or cargo compartment. Trunk is used in North American English and Jamaican English; boot is used elsewhere in the English speaking world. Trunk is also primarily used in many non-English speaking regions, such as East Asia. In earlier usage, a boot was a built-in compartment on a horse-drawn coach, used originally as a seat for the coachman and later for storage.
The cargo compartment is most often located at the rear of the vehicle. Storage areas are normally at the other end of the vehicle to which the engine is located. Some mid-engined cars (such as the Ferrari 360) and rear-engined cars (such as the Volkswagen Beetle) have it in the front. Vehicles such as the Volkswagen Type 3, had storage compartments in the front and in the rear, above the low profile boxer engine. The mid-engined Fiat X1/9 also had two storage compartments, although the rear one was very small.
Open or closed
This loadspace may further be categorised as open or closed.
Open loadspaces are those found in station wagons (estate cars) and SUVs. Closed loadspaces have a decklid and are typically those found in saloon (sedan) or coupé bodies. The loadspace is separated from the passenger compartment by rigid elements of the vehicle body and trim. Closed trunks are generally trimmed in simple materials whereas many station wagons are trimmed with higher cost and better looking materials as the loadspace forms an extension of the passenger compartment. In order to achieve privacy and or protect the contents of the vehicle from theft or excessive heat, a loadspace cover may be fitted, This may take the form of a rigid parcel shelf, typical of many hatchback vehicles; or in the case of station wagons, cars and many SUVs, a roller blind in a removable cassette.
To increase the flexibility of the trunk loadspace, the addition of folding rear seats increases the size of the trunk and so allows the occasional transport of luggage that would have otherwise required a much larger vehicle. Some manufacturers of smaller and even saloon/coupé-bodied cars offer this flexibility to their otherwise closed loadspaces and so blur the lines of definition by adding folding rear seats to allow the occasional transport of bigger loads.
Active and passive safety
Active safety by luggage retention
The loadspace can contribute to the active- and passive safety of the vehicle. Active safety may be promoted in vehicles that are partially loaded. Here the use of lashing eyes to restrain luggage can prevent or reduce damage to the vehicle and its occupants in severe manoeuvres. In driving while cornering 'in-extremis', the prevention of sudden weight transfer due to poorly loaded luggage can be enough to prevent the vehicle losing grip, and potentially avoiding thereby an accident; active safety.
Passive safety by luggage retention
If a crash should occur, lashing eyes can reduce the severity of outcome of the accident by keeping the luggage in the loadspace compartment and thereby preventing projectiles from harming correctly restrained passengers in the passenger compartment. These lashing features may be in the form of fixed or foldable loops or in the case of certain European vehicles (for example BMW X3, BMW X5, and various VW and Audi models) combine sliding loops in a rail system to allow optimal positioning of the lashing eyes. At the same time this eases the integration of accessories for loadspace management; dividers, bike carriers etc. into the interior of the vehicle, a principle that has been applied in cargo vans and air transport for many years.
In vehicles with open luggage compartments, some are fitted with metal grids or guards to retain loose items in case of collision, or to simply create a bulkhead between the load in the trunk - for example animals - separated from the otherwise unprotected passenger space. Another solution for items that have not been restrained is the loadspace barrier net. These may be directly attached to the body structure or, in vehicles with loadspace cover cassettes, as a combined loadspace cover and barrier net (ger. Kombirollo), the net confining luggage to the loadspace in case of emergency braking and minor crash impacts. These nets have the advantage over metal guards that they can be rolled-up when not in use, taking up much less space than a comparable guard. A guard may however be tailored for an even tighter fit to the body interior contours than a roll-away net.
Beyond carrying luggage, the trunk/boot of most passenger vehicles commonly contains various other components often behind the trimmed surfaces of the interior. These components may be accessed by the customer or the service personnel through (in some cases lockable) hatches in the trim, or by removing carpet and support boards etc. Typical components:
- Spare tire
- jack and lug wrench
- on-board tool kit for do it yourself repairs
- electronics for sound, video, GPS, etc.
- Battery and hybrid energy store (see plug-in hybrids).
- Fuse boxes
- CNG/LPG tanks (for bivalent engines)
- Additional folding, or 'third-row', seating (increasingly in open loadspaces)
Children trapped in trunks can die of suffocation or heat stroke. Once in the trunk, they may not be able to get out, even if they entered through the interior, because many rear seats only release to the trunk from inside the passenger area.
Shelves and boards
Some vehicles offer configurable cargo conveniences such as a shelf or board. They often serve various purposes. The multiposition rear shelf on the Chrysler PT Cruiser can be used as a table for a picnic, a second cargo layer, or a security screen. The Citroën C3 has a foldable segmented false floorboard that compartmentalises the cargo area, makes loading easier, and evens out the load floor when the back of the rear seat is folded down.
The locking of the trunk may be achieved together with the passenger compartment.
Some cars include a function to remotely open the trunk. This may be achieved through a variety of means
- release of the latch whereby the doorseals push the decklid away from the lock, the trunk is then open, and the lid may not have revealed the opening.
- release of the latch whereby a spring pushes the decklid away from the lock and open, the trunk is then open, and the lid reveals the opening.
- release of the latch and actuation of a drive, whether hydraulic (BMW 7 Series) or electric (BMW X6), which pushes the decklid away from the lock; the trunk is then open, and the lid reveals the opening. This may then be electrically closed again.