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Airbag update - The inflatable seatbelt airbag

Technology update February 2011

February 2011

Automobile manufacturers are continually trying to improve occupant protection and safety during a collision scenario. At the same time vehicles become ‘safer’ for the occupants, these improvements will also continue to challenge rescuers to ‘know what’s inside’ when performing extrication. Both Ford and Lexus are bringing inflatable seatbelt airbags to the market this year. This newsletter will examine information about each system!


Ford's rear inflatable seat belt functions like a standard seat belt in normal everyday use. The vehicle's crash sensing system determines when the inflatable belt should deploy. The inflatable belt deploys slightly before other air bags during a crash. In a blink of an eye, the tubular air bag rapidly inflates across the body. The fully inflated belt helps distribute crash force energy across five times more of the occupant’s body than a traditional belt, which expands its range of protection to help reduce injury risks.


The SRS seat belt airbag (also called 'airbelt' by its manufacturer) being fitted in the Lexus LF-A has an airbag built into the webbing of the seat belt, which inflates on impact to provide additional protection to the shoulder and critical head area. Unlike the inflatable seatbelt on the Ford Explorer, which is intended to deploy mainly on frontal impacts, the SRS seat belt airbag will also deploy in side impact collisions, to reduce lateral head movement and provide protection from impact with the side window or colliding object.


The function of both airbag applications is similar: A cylinder of compressed gas is housed at the seatbelt buckle on the Lexus LF-A's front seats and under the Ford Explorer's rear seat cushion. The cylinder expels gas to the seat belt in case of a collision. The buckle assembly and the seat belt tongue are designed to allow gas to pass through it to the seat belt airbag. The tubular airbag is built into the shoulder strap of the seatbelt and inflates with the compressed gas through a fill tube. The lap belt webbing does not inflate as it is the same as a standard seat belt webbing, but has its own retracting system, which (in the case of the Lexus LF-A) is fitted with a seatbelt pretensioner.


'From an extrication point of view there are a few things to consider’ says Moditech’s extrication expert Jörg Heck. 'The volume of the airbag is very small and it has been developed to deploy directly on the body of the occupant and is therefore not as dangerous as other deploying airbags. If necessary the seatbelt can easily be cut.  However since the belt does not slide through the latch buckle as normal and both the shoulder and lap portions of the belt have separate retractors, rescuers will need to cut the belt twice - the shoulder belt above the airbag, and also cut the lap belt.' ’As with all other vehicles, there are always components that should not be damaged - and therefore avoided - during rescue operations. Knowing what's inside is essential when dealing with the complexity of modern vehicles. In case of the inflatable seatbelt rescuers should avoid damaging the buckle of the inflatable seatbelt as long as the bag is undeployed; for instance when working with hydraulic rams or cutters.’ says Heck. ‘Therefore the inflatable seatbelt and it’s inflator is now also shown in the Crash Recovery System.'