High-Tech Vehicle Safety Systems

Side Air Bags

Side air bags are inflatable restraints that provide head and chest protection for vehicle occupants involved in nearside impacts. Chest protection is provided by torso bags, or combination head and torso bags, that are installed in the side door of the vehicle or in the seatback. Head and torso bags feature an upper lobe in the bag's fabric that cushions the occupant's head. Alternatively, head protection may be provided by an inflatable tube or curtain that is stowed in the vehicle's side roof rail.

How do they work?

Torso side air bag

Torso side air bag

Side air bags function in much the same way as front air bags. When sensors in the vehicle determine that a side impact is occurring, the control computer sends an electrical signal to ignite the pyrotechnic gas generator. The gas flows rapidly into the air bag fabric. The air bag expands and bursts out of its stowage location, providing an inflated cushion between the occupant and the vehicle interior.

Early systems employed only torso bags designed to protect just the chest. Most current vehicles now also feature head protection by means of a combination head and torso bag or some form of head curtain.

In side crashes, even belted occupants can strike their head against the side interior of their own vehicle, or part of an impacting vehicle or object. Head curtains typically cover the full area of the side windows, preventing partial ejection of any occupant's head through the window area, and providing a cushion against head contact with the window glass or frame, or with an impacting vehicle, a pole, or a tree.

Combination head and torso side air bag

Combination head and torso side air bag

Are there any risks?

An early concern with side air bags, especially torso bags, was the potential hazard to small children who might be out of a normal seating position, for example asleep with their head against the side interior of the vehicle, and in the direct path of the air bag should a deployment occur.

Motor vehicle manufacturers and Transport Canada have an agreement that the design of side air bags will meet the requirements of test protocols recommended by the Side Air Bag Out-of-Position Injury Technical Working Group in order to minimize any such hazard. For more information, see How to Protect Children in Vehicles with Side Air Bags.

Side curtain deployed over both side window openings

Side curtain deployed over both side window openings

What can science tell us?

  • Surviving Side Crashes; Status Report; IIHS; Vol. 41 No. 8; October 7, 2006 Side air bags that protect the head, chest, and abdomen during a collision were found to reduce driver deaths in cars struck on the near (driver) side by an estimated 37 percent. Airbags that protect the torso (chest and abdomen) but not the head are reducing deaths by 26 percent.
  • The Influence of Side Airbags on the Risk of Head and Thoracic Injury after Motor Vehicle Collisions; McGwin G, Metzger J and Rue LW; Journal of Trauma-Injury Infection & Critical Care, Vol. 56 No. 3; pp. 512-517; March, 2004
    Using data for side impact crashes taken from the U.S. National Automotive Sampling System Crashworthiness Data System (NASS-CDS) the authors estimate that occupants in vehicles equipped with side air bags providing head protection had a 75% lower risk of head injury, and those with side air bags offering chest protection had a 68% reduction in thoracic injury risk.
  • Efficacy of Side Air Bags in Reducing Driver Deaths in Driver-Side Collisions; Braver ER, and Kyrychenko SY; American Journal of Epidemiology; Vol. 159 No. 6; pp. 556-564; March 15 2004
    The effectiveness of side air bags in reducing driver deaths in side impact crashes was examined using data from the U.S. Fatality Analysis Reporting System (FARS) and the General Estimates System (GES). Risk was reduced when cars with head/torso air bags were struck by cars/minivans or pickup trucks/sport utility vehicles. Head/torso side air bags appear to be particularly effective in reducing nearside driver deaths.
  • Assessment of injury risk to children from side airbags; Tylko S and Dalmotas D; SAE Paper 2000-01-SC02; November, 2000
    Static out-of-position tests were performed with child dummies to identify the potential for injury. Tests conducted to monitor child seat and airbag interactions confirmed that properly restrained children would not be exposed to undue risk from a deploying side airbag. Results of the out-of-position testing suggested that current side airbag designs may cause serious and/or fatal neck and chest injuries.
Crash test between a car and a sport utility vehicle

Crash test between a car and a sport utility vehicle

Side impact with a utility pole

Side impact with a utility pole

Useful links

Quick Facts

  • Always wear your seat belt; air bags only provide additional protection!
  • Side airbags may be located in the door, seatback and/or the roof side rail
  • Young children should be placed in appropriate child restraint systems
  • Check the owner's manual for specific information about the air bags and seat belts in your vehicle

Associated systems:

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