By Salvatore Salamone

Automakers have greatly improved your odds of surviving a front- or rear-end crash, but the same can't be said, just yet, for side-impact crashes. These crashes account for 28 percent of all fatalities, the majority of which are caused by brain injury, according to the National Highway Traffic Safety Administration (NHTSA).

Over the years, improved structural designs, standard airbags and increased seatbelt usage have helped reduce overall driver death rates. However, side-impact crash rates have decreased significantly slower than frontal crash rates.

To improve side-impact safety, carmakers face a serious hurdle in terms of crash dynamics. A great portion of the impact of a head-on or rear-end collision can be absorbed using crumple zones and the large amount of metal between a car's bumper and the passenger compartment. Additionally, occupants in front-end collisions today have the added protection of standard airbags.

Side-impact crashes, on the other hand, present more danger to a car's occupants, because the side panels are structurally weaker and thinner. Basically, a car's frame and door are all that sit between the object hitting the car and the occupants. Additionally, the height difference between, for example, an SUV and a passenger car is more of a problem in side-impact crashes, since the bumper of an SUV can be at window glass level — an area that is particularly unsuited for absorbing a crash.

Technology Developments Address Side-Impacts

Today, many auto manufacturers offer optional in-door airbags to help protect car occupants in the event of a crash. But even these don't reduce the danger sufficiently.

One effort to address this issue is a European Union-funded project called APROSYS. The project seeks to develop an adaptive safety system that would use side sensors and sophisticated algorithms to anticipate a crash and then take steps to protect the occupants.

"Our goal was to improve the active crash safety of motor vehicles — that is, to adapt the technical properties of the car body in such a way that it absorbs energy at the crucial moment and thus protects the occupants," says project manager Björn Seipel of the Fraunhofer Institute. Fraunhofer developed much of the technology for this project in conjunction with researchers at other universities and auto manufacturers.

The experimental APROSYS system uses stereo cameras within a car's door, radar sensors to continually scan the near-car environment and a computer to analyze the information. When a crash is predicted, metal bars are inserted into the door and frame about 200 milliseconds before the crash. This strengthens the frame and transfers some of the energy of the impact to the chassis and the un-struck side of the car.

The reason for the complexity is that the protective bars cannot be placed permanently; if they were, the windows wouldn't roll down. Instead, the idea is to use a mechanism like a spring-loaded or compressed air-powered trigger that would deploy the bars when needed. A similar approach is already being used in conjunction with sophisticated electronic sensors to quickly deploy roll bars in some convertibles.

Additionally, automakers might address side-impact crashes by borrowing technology from other safety-related efforts already underway. For instance, blind-spot detection and lane-departure warning systems might be used to identify the precursors to a crash. Similarly, the systems developed to assimilate information for the U.S. DOT's Integrated Vehicle-Based Safety Systems (IVBSS) initiative might be useful in anticipating (or even avoiding) a side-impact crash.

Other Protective Measures for Side-Impact Crashes

While the technology used in the APROSYS project undergoes tests and is proven out, automakers are trying other measures to help protect car occupants in side-impact crashes.

Common approaches taken today to improve safety include adding in-door airbags, as we've mentioned and strengthening a car's B-pillar, which is the vertical support between the driver and passenger doors and windows. For instance, Volvo, Mercedes, General Motors and others have strengthened B-Pillars or front door trim panels.

Another area being investigated is adding more rigidity to car seats to help physically protect the occupant in a crash and to dissipate the energy from the impact to other parts of the car.

To date, much of the side-impact crash protection work has been voluntary. Automakers are not subject to mandates in this area. But that is about to change. Last year, the U.S. Department of Transportation announced new side-impact safety requirements for all passenger cars. The new standard requires head protection in side-impact crashes. NHTSA estimates that the new requirements will save over 300 lives and prevent nearly 400 serious injuries per year.

Fortunately, most automakers planned to add such protection in 2009 cars. And while many will offer in-door airbags as an option next year, the offering is likely to become standard by 2013.

Bio: Salvatore Salamone is a senior editor at Ziff Davis Enterprise. He has more than 20 years of experience writing about science and technology for major industry trade magazines and is the author of three business technology books.