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Protecting Pedestrians Through Vehicle Design (3)
Changes to Vehicle Design
To respond to this wide range of scenarios, automakers began addressing pedestrian accidents decades ago by focusing on the obvious vehicle features that could cause harm. Protruding hood ornaments, for example, were embedded in the grille or designed to collapse on impact, while exterior mirrors are now mounted on springs. Even a styling feature such as recessed door handles has helped reduce pedestrian injury.
In recent years, vehicle design has focused on making subtle changes to the front end of the vehicle that are not obvious to consumers. One example is changing the way that the fenders, hood and windshield wipers are attached, so their performance strength is maintained but they can easily collapse when impacted by a pedestrian. Vehicles from Acura, Honda, Infiniti, Lexus, Nissan, Toyota, Volkswagen and Volvo among others have these types of features.
Hood design and engine compartments have also received many subtle design changes. Today the vast majority of vehicles sold in the U.S. have braces supporting the hood that crush when they are impacted from above, such as by a person's head. In addition, a plastic engine cover serves to soften the impact, as does increased space between the hood and the cover. Beginning in 2001, Volvo, for example, decided it needed 3 inches of deformable space between the hood and engine in its new vehicles for pedestrian safety. As a result, when it came time to decide between two V8 engines for its XC90, one engine was ultimately rejected for the sole reason that it protruded into the company's 3 inches of required space.
One key area still challenging engineers in most U.S. vehicles is the front bumper. For vehicles in Europe and Asia (where there are many more pedestrian collisions and governmental standards regulating them), bumpers are designed with larger crush space and with different supports for the plastic bumper cover in order to reduce leg injury. Unfortunately, these "softer" bumpers don't perform well in the 5-mph bumper test conducted by the Insurance Institute for Highway Safety (IIHS) to assess repair costs, so they generally aren't used on vehicles in the U.S.
Another issue with bumper design for U.S. vehicles relates to the front airbag sensors that are located in the bumper. "Because of the sensor location, it can be difficult to address pedestrian safety and still have the sensors effectively trigger the front airbags, particularly in low-speed collisions," explains Max Gates, spokesman for the Chrysler Group. One way to provide added pedestrian protection while still performing well in the IIHS bumper test is by adding high-density foam behind the plastic bumper cover, a method used on all Toyotas.
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