Inflatable seatbelts
Inflatable seatbelts; photo by Peter Bleakney. Click image to enlarge

By Jim Kerr

A majority of vehicle safety technology – padded dashes, recessed control knobs, collapsible steering columns, front airbags, side airbags and even knee airbags – are all designed for those in front. In recent years, second and third row occupants have benefited form side curtain airbags and seat belt pre-tensioners, but now Ford has developed a new safety device for rear seat passengers that not only improves safety but is more comfortable too. It’s the Inflatable seatbelt and it has been chosen by the Automobile Journalists Association of Canada (AJAC) as the “Best New Technology” on the Canadian market.

The inflatable seatbelt is deceptively simple. When you see the parts involved, you may ask why it wasn’t introduced before, but the technology and testing involved in getting a product like this to production are immense – but then so are the benefits.

Here is how it works: the inflatable seatbelt is used like every other seatbelt. Slide into the seat and buckle up. It works for adults, small children and front and rear facing child seats. A computer for the air bag system monitors sensors and during a collision that could injure an occupant, the seatbelt inflator module is activated. A small cylinder, not much bigger than the seatbelt buckle, is located beneath the seat. The computer fires a small pyrotechnic charge to release the compressed gas inside the cylinder, where it travels through a tube connected to the seat belt buckle. The seatbelt latch has a corresponding passage internally so that when the seat belt is connected, the gas will pass through the latch and into a long cylindrical airbag tube folded inside the seatbelt material.

The airbag tube will break through the edge stitching of the seatbelt fabric and inflate, expanding across the occupant’s body to hold the occupant in place and distribute the impact energy of a collision across the body. Tests show that it distributes this force five times more than a conventional seatbelt, while the inflated airbag helps support the head and neck during the impact.

Some of the design considerations for this technology were, of course, safety to occupants using the belt, and durability. In addressing safety, Dr. Srini Sundararajan, leader of development for the seat belt design described how the system used a cold inflation system instead of hot expanding gases as used in many frontal airbags. With the seatbelt holding the occupant in place, the charge had to be cool so it would not burn occupants.

The seatbelt airbag also inflates with a much lower pressure and slower rate than a conventional airbag. The seatbelt is already in contact with the occupant, so it doesn’t have to move far. This allowed a slower fill. The pressure is low enough that the seatbelt airbag will inflate around objects such as the holes in a child seat or around someone holding the belt with their hand. The belt gently pushes out to protect.

In testing, Ford monitored the belt operation in every conceivable way it could be used or misused. Sitting out of position, sitting with the seatbelt behind you, falling asleep with your head draped over the belt, the system was tested for all ages. The system has been in the works for approximately 10 years.

Durability and accidental damage were also tested. Dr. Sudararajan described how they soaked the inflatable belt in meat juices and had a large dog chew on the belt to simulate the damage that might occur if you left a dog in the vehicle. The belt operated properly even after being mauled.

This seatbelt system is also designed to inflate only if the belt is buckled, saving on insurance repair costs if there is nobody in the seat when a collision occurs.

One side benefit of this seatbelt design is that it is more comfortable to wear than a regular belt. The folded airbag inside the belt gives it a padded feel and the edges of the belt are rounded to hold the airbag. How many times have you readjusted your seatbelt because the edge of the belt was cutting into your shoulder or neck? The rounded edge feels much more comfortable.

Ford’s Inflatable seatbelt will be offered as an option on the 2011 Explorer first, but with the benefits it offers, I can see its use expanding not only across Ford’s line-up but across the industry as well. That is what makes this technology the best of the year.

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