Potential Safety Benefits of Lane Departure Warning and Prevention Systems in the U.S. Vehicle Fleet
The objective of this study was to compare the predicted safety benefits of lane departure warning (LDW) and lane departure prevention (LDP) as if all vehicles in departure crashes in the U.S. fleet were equipped with either system.
- LDW works by alerting the driver, via an auditory, visual, or haptic warning, of a lane departure and relies on the driver to respond to the departure event.
- In contrast, LDP can directly modulate vehicle trajectory using various modalities, including steering or selective braking of the vehicle’s wheels.
Two measures of safety benefits were evaluated: (1) the number of crashes that could have been avoided were investigated, and (2) the number of seriously injured drivers that could have been prevented.
A set of 478 road departure crashes extracted from the 2012 National Automotive Sampling System Crashworthiness Data System (NASS/CDS) were used to formulate a simulation case set. The simulation case set in this study included only single vehicle crashes where the driver drifted out of their lane, and excluded other single vehicle crashes, such as control loss or contact with animals in the roadway. Parameters required for the simulations such as the shoulder width of the road, the travel lane of the vehicle, and lane markings are not coded in the NASS/CDS database and therefore were determined through manual review of scene evidence.
Each of these crashes were than simulated with and without LDW and LDP systems. The LDW system was assumed to alert the driver at the instance the leading wheel touched the lane marking, with reaction times varying between 0.38 s and 1.36 s. A steering-based LDP system was assumed to operate in conjunction with LDW (i.e. by alerting the driver of a lane departure) and directly modulate steering wheel angle at the instance the leading wheel touched the lane marking. Four hypothetical LDP designs were evaluated, using typical evasive maneuvering behavior from a lane departure, to be representative of "light" , "moderate", "aggressive", and "autonomous" steering.
Benefit 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 or LDP.
- The LDW system was estimated to reduce the number of crashes by 26.1 percent and the number of seriously injured drivers by 20.7 percent.
- The light steering to aggressive steering LDP systems were estimated to reduce the number of crashes by 32.7 percent to 37.3 percent and the number of seriously injured drivers by 26.1 percent to 31.2 percent. The LDP system with autonomous driving characteristics were estimated to reduce the number of crashes by 51.0 percent and the number of serious injuries by 45.9 percent.