Side impact: front and center: the seriousness of such crashes and a new proposal from NHTSA puts side impact back under the microscope

Automotive Industries, Sept, 2004 by Rich Wilson

The reality of the violent and often fatal side impact collision is anything but a new topic for automotive safety professionals. Safety technologies to help lessen the effects of these horrific crashes have been evolving for years.

"Either your head hits the oncoming tree of pole, or your head hits the hood of the oncoming vehicle, that's the typical mode of death on a side impact. These are not the only ones, but certainly the most predominant," says Doug Campbell of TRW.

New proposed additions to NHTSA's 214 standard (the one governing side impact) have reinvigorated the safety collective consciousness at OEMs, supplier companies, and NHTSA itself. Auotmotive Industries sat down with a number of these professionals and let them shed some light on the issues and technologies that will come into play to lower fatality rates.

Airbags

Bob Yakushi, director of product safety for Nissan North America, walks us through Nissan/Infiniti's history with supplemental restraint systems designed for side-impact.

"We had side airbags, seat-deployed thorax/head combination bags, around 1998 on the G20 models. That's when we introduced our first thorax/head air bag. The shape is an upside down L. Prior to that, we had offered thorax (only) bags. We did some research in the mid'90s that showed that if you could offer head protection you could mitigate head injuries by 80-90 percent. This research led us to phase out the thorax (only) bags and introduce the head/thorax bag. We now offer some type of side airbag on all our models.

"We've been going towards curtain airbags applications as we have new models. It's not as simple as just adding a curtain to the vehicle--for instance the Sentra is still equipped with the head/thorax combination bag."

One of the big advantages to the side curtain airbag over the head/thorax bags, according to Yakushi, is the ability to provide rear seat coverage. Yakushi went on to say that every Nissan offers side impact coverage to each passenger row in the vehicle.

"For example, on the Armada and Quest we cover three rows and to do that there's one airbag (side curtain) to cover the first two rows and then a second bag cover the third row," he says.

Yakushi explains further that the side impact defense strategy starts with the primary energy absorption structure, the body of the vehicle. The vehicle structure is the primary focus. The airbags are supplemental systems to the structure. Nissan features a zone body construction that has crushable front/rear area and utilized higher strength steels in the passenger area. Reinforcing door beams can either be tubular of flat.

"As safety technology evolves, we then look at applying those safety technologies as they become feasible and as they meet our internal criteria," Yakushi says. "There's governmental criteria, voluntary criteria and Nissan, of course, has its own internal criteria. As systems are developed that meet our criteria for performance, then we will start to apply those to our vehicles.

"The evolution from the seat mounted airbags into curtain airbags is the evolution of the vehicle platform. In order to apply a curtain airbag system you have to have the vehicle structure and a system developed specifically for that vehicle platform."

Airbag manufacturer Autoliv explains that head/thorax bags have a higher propensity for inducing an injury based on the deployment strategy: The side curtain down airbag is not a concern as far as inducing injury. Also, the head/throrax bag isn't going to be useful for keeping the occupant inside the vehicle. The side curtain bag does offer a chance to keep extremities inside the vehicle as well as provide some protection against rollover.

The evolution of the technology was one of the factors that lead to the availability of side curtains with the biggest change in the bag itself.

"These bags look like an air mattress that you'd lay on and you have extremely high pressures to deal with. It was important that the bag be woven because then each strand of nylon could be controlled by computer," says Patrick Jarboe, director of communications for Autoliv. "When air bags are sewn, that can change the structural integrity."

Doug Campbell, vice president, engineering/occupant safety systems and Ayad Nayef, manager, systems performance, side impact and rollover systems from TRW detailed some of TRW's airbag inflation technologies.

"They originated (side airbags) in Europe at our design center. Our customer base was asking for them and we've been in production for the last five to six years, in Europe, on side curtains and seat deployed bags. We've been going in this direction for a number of years. The current marketplace competition has more such options coming to American and Japanese vehicles and then, of course, Ford came out with a rollover bag, an extension of the other technologies, requiring different bag design and inflator technology," Campbell says.

TRW sights Mercedes door-deployed side impact bag as one of the earliest types of side impact systems. The company moved away from the technology due to positioning concerns.