Since airbags have become commonplace in cars in the last two decades – yes, it's been that long – we have seen all sorts of different airbags in different locations to protect against various crashes. Now Mercedes is adding a new airbag of sorts to its 2014 S-Class. This newfound device is called the beltbag.

Here's how the beltbag works. When the car is involved in a crash, the rear seatbelts will inflate with air and help cushion the seat's occupant against torso damage caused by the belt. If you've ever been in a hard enough crash to jar you forward, you know how badly a seatbelt can bruise your chest and abdomen. The airbelt is supposed to prevent that damage.

This isn't the first airbelt to be released though, as Ford included it in its optional features on the 2011 Explorer. This is, however, the first time it is a standard feature. We are curious as to why Mercedes->ke187 did not add this feature to its front seatbelts, as the jolt forward is no different in the rear than it is in the front.

We also wonder how many years this will remain an optional feature before the NHTSA decides that this needs to be standard in all cars, thereby driving up the cost of a new car even more... Keep in mind, even front airbags were once only an option, as were tire pressure monitors, traction control, and ABS. Now those features are all required, in one for or another, on all cars sold in the U.S.

We'll get to see this new belt system in action in Geneva next spring, which is when Mercedes-Benz unveils its new S-Class->ke359.

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