The Influence of Roadway Characteristics on Potential Safety Benefits of Lane Departure Warning and Prevention Systems in the U.S. Vehicle Fleet
Lane departure warning (LDW) and lane departure prevention (LDP) systems are active safety systems that have the ability to mitigate crashes and injuries by alerting drivers of a lane departure and/or directly modulating vehicle trajectory. The objective of this study was to determine the limiting influence of shoulder width and lane markings on the effectiveness of LDW and LDP. Real-world road departure crashes were simulated without LDW/LDP, with LDW, and with LDP. These crashes were then simulated again on roads with improved infrastructure, (i.e., with lane markings and a 3.6 m shoulder width).
A total of 478 representative crashes from the 2012 National Automotive Sampling System Crash Worthiness Data System (NASS/CDS) were used in this study. The sample set included single vehicle crashes where the driver drifted out of their lane and departed the roadway. Crashes that involved control loss or animals in the roadway were excluded.
Vehicle kinematics simulations were performed using CarSim vehicle simulation software. Driver control was modelled using a previously implemented driver recovery model developed by Volvo, Ford, and University of Michigan Transportation Research Institute (UMTRI). As the vehicle approached the edge lines of the road, the driver model considered the yaw of the vehicle, identified if that yaw would cause lane departure, and made a proportional change to the yaw rate to maintain vehicle position in the lane. Driver steering was assumed to begin after the driver departed the paved roadway or after being alerted by an in-vehicle LDW or LDP system.
The LDW system was modelled as alerting the driver at the instance the leading wheel touched the lane markings. The LDP system was assumed to work in conjunction with the LDW system to alert the driver of a lane departure.
Benefits estimates were performed in three steps:
- A probability of crash was computed for each of the simulated trajectories.
- Probability of a seriously injured driver (Maximum Abbreviated Injury Score of 3 or greater, MAIS3+) was estimated from previously developed logistic regression functions.
- Benefits estimates were computed to determine the proportion of crashes and seriously injured drivers that could have been prevented if the vehicle had been equipped with LDW / LDP.
LDW and LDP were estimated to prevent 59 percent and 67 percent of crashes, respectively, when the shoulder width was at least 3.6 m. In contrast, when no shoulder was present, LDW was found to have no effectiveness and LDP was estimated to prevent 1 percent of crashes. The influence of shoulder width on benefits is especially important when considering that 29 percent of crashes occurred on roads with no shoulder.