Motor vehicle accidents are one of the most important causes of deaths, hospitalizations, treatments and disabilities among non-intentional injuries in Japan. Sudden unintended acceleration (SUA) during an accident is a serious issue that leads to numerous cases of critical injuries and even death every year. In 2008, over 6,500 cases of SUA occurred in Japan, which resulted in the death or injury of approximately 10,000 people (Ministry of Land, Infrastructure, Transport and Tourism, Japan [MLIT], 2009). In this study, twenty young drivers (YDs) and twenty older drivers (ODs) participated in six accelerator or brake pedal press tasks with different visual stimuli under one foot or both feet. We recorded the reaction times (RTs) and pedal error rate for all the conditions. Both the RTs and the pedal error rate of both the YD and OD groups significantly increased with the difficulty of the task. Other than the simple reaction condition, we found that the pedal error rate of the OD group was significantly higher than that of the YD group; the OD group also had longer RTs. Moreover, the rate of accelerator error was consistently two or three times higher than the rate of brake error for both the YD and OD groups. We proposed that human decision making is one of the major factors that leads to pedal errors during driving. Moreover, the impairment in decision making observed in older drivers is one factor that might contribute to a high incidence of SUA-related accidents.