Vehicle Active Safety Systems for Preventing Road Departure Accidents

On U.S. highways single-vehicle road-departure (SVRD) accidents account for approximately one fourth of all accidents and one third of all fatalities. This paper describes an active safety system to help prevent SVRD accidents. Many aspects of the proposed system have been implemented on a prototype vehicle, and evaluated in driving tests. In addition to providing an overview of this vision-based system the development and performance of some of the key subsystems is highlighted. These include subsystems to estimate lane geometry, vehicle trajectory, time-to-lane-crossing, driver state, vehicle yaw rate, and to provide driver warning, steering assist and/or brake-steer intervention. Two of the subsystems are described in more detail. First the use of accelerometers for estimation of the yaw rate, then the development and performance of a robust steering assist controller. Also, simulation tools for development and validation of the active safety system are described. INTRODUCTION On average every minute, somewhere in the world, a person dies from a traffic accident. As shown in Fig. 1, singlevehicle-road-departure (SVRD) accidents account for approximately one fourth of all vehicle accidents and over one third of all fatalities in the U.S [NHTSA, 1999]. The degradation of driver performance during a long driving task can be a direct cause of SVRD. A fatigued or impaired driver during highway driving is an obvious example. Recently driver distraction (e.g., cellular phones, navigation systems) has received considerable attention. This paper describes research to develop lateral active safety systems to help drivers by preventing SVRD accidents. In contrast to passive safety systems such as air bags and seat belts, active safety systems have the potential to prevent vehicle crashes before they occur. Since both the driver and the active safety controller can have control over the vehicle steering, the interaction between the driver and the controller must be carefully considered, and the problem is quite different than the problem of lateral control in an automated highway [Shladover et al, 1991; Hedrick et al 1994; Rajamani et al 2000]. Figure 1. Single vehicle road departure accidents on US highways, (a) crashes, and (b) fatalities This paper provides an overview of a vehicle active safety system for preventing SVRD accidents, including research on various subsystems and their development, and describes implementation of the system on a prototype vehicle. The system development and validation relies on vehicle simulation Number of vehicle crashes SVRD