"Unintended Acceleration": Human Factors Engineering Issues and Solutions

Abstract

In the first few months of 2010 the news media reported numerous instances of “unintended acceleration”. Vehicles were recalled because a floor mat was thought to be snagging the accelerator pedal. However, some vehicles that had gone through the recall still experienced unintended accelerations, indicating that the problem also lay elsewhere. In the 1980s there were recalls of over 100,000 Audi vehicles with automatic transmissions in which drivers had reported unintended accelerations. Earlier cases had also been reported (Mortimer, 2011), so the issue is an old one. As a result of such runaway events, primarily in vehicles with automatic transmissions, automakers equipped them with shift-interlocks, so that the vehicle could not be moved into either a forward or reverse gear after starting the engine unless the driver’s foot was depressing the brake pedal. About 83% of unintended acceleration events were reduced by this device (Schmidt, 1993), confirming the role of driver pedal misapplication when starting out. Other studies found that drivers show pedal confusions also when the vehicle is under way. Those events are not reduced by the shift-interlock. Rogers & Wierwille (1988) found about 0.2% of foot movements resulted in a “serious” pedal misapplication error in a simulator. Tomerlin & Vernoy (1990) found that 1 of 169 of their drivers stepped on the accelerator instead of the brake and continued to do so in a driving test. Such results show that drivers “frequently” make pedal errors, especially when considering that there is about one brake application per mile (Mortimer et al, 1970) in the U.S. The panel members will discuss the human factors issues that cause pedal misapplication in various types of vehicles and their frequency, including crashes that result. The thrust of the discussions will be on how our present knowledge can be used to reduce these hazardous events and to discern what additional information is needed to solve the “unintended acceleration” problem.