A Combined Brake-accelerator Pedal and Its Evaluation

Over the years designers have developed various combined brake-accelerator pedals in an effort to eliminate the operator’s risk of pressing the wrong pedal as well as to reduce his or her reaction time in braking. The goal of this study was to highlight problems that drivers may face when they switch between pedal systems. Eighteen male and female drivers varying in age participated in the study. The evaluation was carried out during special driving maneuvers and in normal traffic in which all drivers used the same test vehicle. The results indicate that drivers were able to learn the new combined pedal mechanism quickly and effortlessly and that the number of mistakes was extremely low during the acquisition phase in learning the new system. Difficulties in assessing risk with pedal systems are discussed and some ideas about future work are suggested. INTRODUCTION Background. Since many years, all cars have had separate foot-pedals for accelerating and braking. This has become standard and there has been rather little dispute about this arrangement. However, some drawbacks are obvious: First, the time it takes to move the foot from the accelerator to the brake adds to brakereaction time. This movement time is about 0.2 seconds. Second, there is risk for misapplications. That is, risk for bad hit of a pedal and, in the worst case, the driver may hit the accelerator instead of the brake. In cars with automatic transmission this may cause so-called “unintended acceleration” (Schmidt 1989) when the driver persists in pressing the accelerator instead of the brake without realising the mistake. To eliminate these drawbacks several combined acceleratorbrake pedals have been suggested over the years. A new Swedish solution invented by Mr Sven Gustafsson have such good features that it motivated a behavioural evaluation financed by the authorities in Sweden. The Gustafsson ́s combined acceleratorbrake pedal. An accelerator-plate is mounted to the end of a brake-pedal lever (see fig. 1). When operating the pedal-system the driver puts the foot, which should be kept there all the time when driving, on the accelerator-plate. When accelerating the driver pushes with the fore-foot and folds down the accelerator like in a conventional vehicle. But when braking the driver reaches out with the leg, still with the foot on the accelerator. The throttle is released as the 13 ICTCT workshop Proceedings Intelligent Transport Systems 248 brake is affected so the driver does not have to release the throttle by lifting the fore-foot before braking. An electromagnet supports the brake-lever to prevent accidental braking during acceleration. For safety reasons an extra brake-pedal is mounted to the left side of the brake lever in case the driver moves the foot away from the pedal in, for example, emergency situations. This extra brake is not visible in the figure.