Field Relevance of the New Car Assessment Program Lane Departure Warning Confirmation Test

The availability of active safety systems, such as Lane Departure Warning (LDW), has recently been added as a rating factor in the U.S. New Car Assessment Program (NCAP). The objective of this study is to determine the relevance of the NCAP LDW confirmation test to real-world road departure crashes. This study is based on data collected as part of supplemental crash reconstructions performed on 890 road departure collisions from the National Automotive Sampling System, Crashworthiness Data System (NASS/CDS). Scene diagrams and photographs were examined to determine the lane departure and lane marking characteristics not available in the original data. The results suggest that the LDW confirmation test captures many of the conditions observed in real-world road departures. For example, 40% of all single vehicle collisions in the dataset involved a drift-out-of-lane type of departures represented by the test. Also, the median total departure velocity for vehicles was 78.9 kph, which is close to the 72.4 kph (45 mph) specified in the LDW test. However, there are some aspects of real-world road departures not included in the test. For example, the test is performed in daylight yet nearly half of all road departure crashes (42%) occurred in the dark. Furthermore, the LDW test is only performed on straight road segments, which corresponds to 48% of real-world departures. The departure speed specified in the LDW test is 0.5 m/s (1.1 mph) whereas the mean lateral departure speed in real world crashes was 4.3 m/s (9.5 mph). Of the examined cases, the LDW test is applicable to approximately 23% of no maneuver road departures, which corresponds to 9% of all single vehicle collisions. Including dark lighting conditions and curved road segments would increase the applicability to 65% of no maneuver departures and 26% of all single vehicle collisions. These results can be applied to the design of future LDW performance tests. CITATION: Kusano, K. and Gabler, H., "Field Relevance of the New Car Assessment Program Lane Departure Warning Confirmation Test," SAE Int. J. Passeng. Cars Mech. Syst. 5(1):2012, doi:10.4271/2012-01-0284. ____________________________________ target speed during the entire test. The vehicle yaw rate must not exceed 1.0 degrees/s. Table 1. Test Matrix for NCAP LDW Confirmation Test. Tests are run on a straight road segment at a low lateral departure velocity [1]. Three types of lane markings are used in the confirmation test: 1) a white solid line, 2) a yellow dashed line, and 3) raised traffic markers, also known as Bott's Dots. Bott's Dots have been adopted in some states, such as California, as an alternative to painted lane markings. They are raised markers that are circular or square that adhere directly to the pavement. They can be retro-reflective or non-reflective. The Bott's Dots marking, while limited to certain localities, is considered difficult to accurately track for most vision-based LDW systems [1]. These test conditions were selected in order to evaluate LDW systems on passenger vehicles. An ideal test would be representative of the environments the systems are likely to encounter in the field. One prominent source of data used to characterize road departure collisions is historical crash databases [2, 3, 4]. These databases usually contain information aggregated from police accident reports and may be supplemented by professional investigators who collect additional information. However, these traditional data sources do not have many data elements that are of importance to an LDW confirmation test, such as lane marking availability and departure velocities. Also, the focus in traditional databases is on the vehicle after it leaves the road. However, of greater interest in evaluating LDW performance are vehicle movements from the point of lane departure to when the vehicle departs the road. This study presents data from a unique crash database that contains supplemental reconstructions focusing on lane departure collisions that were not used in the design of the LDW confirmation test.