Improvement of warning lag time in forward collision warning systems based on multifunctional warnings

We present an improvement of forward collision warning (FCW) by adding more layers of warning functionality based on five stages of crash timeline. Generally, FCW operates at stage 3, the critical moment before crash. The added functionality is the location-based warning (LW) which warns the driver when driving toward a dangerous spot with high speed. LW operates at stage 2, an open condition to crash which comes from bad driving habit. We propose the use of warning lag time as a performance indicator, which is appropriate for real driving experiment. The warning lag time is defined as the time period between the issue of warning and the execution of brake by a normal driver. We performed real driving experiments with normal drivers and compare their brake actions with warnings from our system. The system with FCW alone achieved an average time lag of 1.47 sec., while the system with both FCW+LW can warn the driver faster with average time lag of 1.32 sec. The accuracy of both systems was about the same at 79%.