In the design of Lane Departure Warning Systems (LDWS), it is necessary to determine the warning timing that does not only ensure the effectiveness of the warning but also reduce the annoyance of the warning. Concerning the relation between the warning timing and the effectiveness of the warning, we have reported the performance of the steering avoidance by an experimental study using a driving simulator. The results showed that it is necessary to keep the time margin longer than 0.9 s for the successful avoidance of lane departure. This paper mainly describes the latter point regarding the relation between the warning timing and the annoyance. We have investigated Time to Departure that means the predicted time margin before the lane departure, when 10 drivers drove a passenger vehicle on 5 kinds of Japanese highways in a metropolitan area. The results show that the accumulated frequency of Time to Departure at 1.0 s is approximately 0.5 percentile, in terms of the frequency distribution of Time to Departure. This means that the frequency of time margin less than 1.0 s is equal to 0.5 percent in the total driving time. Further analysis concerning the relation between the frequency of warning output and the annoyance might be necessary. But, it can be seen from the investigations that the annoyance will be reduced when the warning timing is set at 1.0 s of Time to Departure, since the frequency of the warning output will be substantially small under normal driving conditions. We regard that these experimental results can be useful for designing the warning timing of LDWS.
Samenvatting