A car bomb, bus bomb, van bomb, lorry bomb, or truck bomb, also known as a vehicle-borne improvised explosive device (VBIED), is an improvised explosive device designed to be detonated in an automobile or other vehicles.
Car bombs can be roughly divided into two main categories: those used primarily to kill the occupants of the vehicle (often as an assassination) and those used as a means to kill, injure or damage people and buildings outside the vehicle. The latter type may be parked (the vehicle disguising the bomb and allowing the bomber to get away), or the vehicle might be used to deliver the bomb (often as part of a suicide bombing).
It is commonly used as a weapon of terrorism or guerrilla warfare to kill people near the blast site or to damage buildings or other property. Car bombs act as their own delivery mechanisms and can carry a relatively large amount of explosives without attracting suspicion. In larger vehicles and trucks, weights of around or more have been used, for example, in the Oklahoma City bombing. Car bombs are activated in a variety of ways, including opening the vehicle's doors, starting the engine, remote detonation, depressing the accelerator or brake pedals or simply lighting a fuse or setting a timing device. The gasoline in the vehicle's fuel tank may make the explosion of the bomb more powerful by dispersing and igniting the fuel.
As a delivery system
Car bombs are effective weapons as they are an easy way to transport a large amount of explosives to the intended target. A car bomb also produces copious shrapnel, or flying debris, and secondary damage to bystanders and buildings. In recent years, car bombs have become widely used by suicide bombers.
Countermeasures
Defending against a car bomb involves keeping vehicles at a distance from vulnerable targets by using roadblocks and checkpoints, Jersey barriers, concrete blocks or bollards, metal barriers, or by hardening buildings to withstand an explosion. The entrance to Downing Street in London has been closed since 1991 in reaction to the Provisional Irish Republican Army campaign, preventing the general public from getting near Number 10. Where major public roads pass near buildings, road closures may be the only option (thus, for instance, in Washington, D.C. the portion of Pennsylvania Avenue immediately in front of the White House is closed to traffic). Historically these tactics have encouraged potential bombers to target "soft" or unprotected targets, such as markets.
Suicide usage
In the Iraqi and Syrian Civil War, the car bomb concept was modified so that it could be driven and detonated by a driver, but armoured to withstand incoming fire. The vehicle would be driven to its target area, in a similar fashion to a kamikaze plane of WW2. These were known by the acronym SVBIED (from Suicide Vehicle Borne Improvised Explosive Device) or VBIEDs. This saw generally civilian cars with armour plating added, that would protect the car for as long as possible, so that it could reach its intended target. Cars were sometimes driven into enemy troop areas, or into incoming enemy columns. Most often, the SVBIEDs were used by ISIL against Government forces, but also used by Syrian rebels (FSA and allied militias, especially the Al-Nusra Front) against government troops.
The vehicles have become more sophisticated, with armour plating on the vehicle, protected vision slits, armour plating over the wheels so they would withstand being shot at, and also in some cases, additional metal grating over the front of the vehicle designed to crush or destroy shaped charges such as those used on rocket propelled grenades.
In some cases trucks were also used as well as cars. They were sometimes used to start an assault. Generally the vehicles had a large space that would contain very heavy explosives. In some cases, animal drawn carts with improvised explosive devices have been used, generally either mules or horses. Tactically, a single vehicle may be used, or an initial "breakthrough" vehicle, then followed by another vehicle.
While many car bombs are disguised as ordinary vehicles, some that are used against military forces have improvised vehicle armour attached to prevent the driver from being shot when attacking a fortified outpost.
History
Car bombs are preceded by the 16th century hellburners, explosive-laden ships which were used to deadly effect by the besieged Dutch forces in Antwerp against the besieging Spanish. Though using a less refined technology, the basic principle of the hellburner is similar to that of the car bomb.