Worldwide, the pace of development in pedestrian countermeasures is increasing rapidly. To better understand the state of the art in bumper design for pedestrian impact, a survey of literature and patents has been performed. Two general approaches to reducing the severity of pedestrian lower limb impacts were identified: (a) Provide cushioning and support of the lower limb with a bumper and a new lower stiffener, or (b) Use the bumper as a platform for impact sensors and exterior airbags. This study focused on the first approach. Excluding bumper sensors, airbags, and non-design-related articles, a total of 130 relevant technical articles and 147 patents were identified.
The most common method proposed for cushioning the lower limb in an impact uses an energy absorber (plastic foam or ‘egg-crate’) in front of a semi-rigid (steel or aluminum) beam. There are also proposals for ‘spring-steel’, steel-foam composites, crush-cans, and plastic beams. The most common method proposed for supporting the lower limb in an impact is a secondary lower beam, known as a ‘stiffener’ or ‘spoiler’. Most proposed lower stiffeners are plastic plates or metal beams supported by the engine undertray, the radiator support, or the front-end module. In addition to these concepts, there are a number of design proposals involving a deploying bumper or lower stiffener.