The safety potential of enhanced lateral vehicle positioning.

Objective: The objective of this study is to estimate the potential safety benefits of Emergency Lane Keeping (ELK) and Autonomous Emergency Steering (AES) systems with precise and reliable lateral positioning.
Methods: The material comprised in-depth studies of fatal road crashes in Sweden in 2017. Crashes resulting in passenger car occupant fatality ( n  = 114) were included; single vehicle ( n  = 60) and head-on ( n  = 31), intersection ( n  = 9), rear-end ( n  = 5), overtaking ( n  = 5), animal ( n  = 1), other ( n  = 1, U-turn), and train ( n  = 2). Additionally, fatal collisions between motor vehicles and vulnerable road users (VRUs) were included; pedestrians ( n  = 36), cyclists/moped users ( n  = 15), and motorcyclists ( n  = 17). A case-by-case analysis was conducted to identify crashes potentially prevented by ELK and AES with precise (within 0.1 m accuracy) and reliable lateral positioning. The identified crashes potentially avoided by ELK systems involved unintentional drift-out-of-lane on roads with posted speed limits of ≥70 km/h (43 mph). For comparison, the same material was used to identify the potential safety benefits of the more traditional lane departure warning (LDW) and Lane Keeping Assist (LKA) systems without enhanced lateral positioning. Crashes potentially avoided by LDW/LKA occurred on roads with visible lane markings and without rumble strips on the departure side while ELK with enhanced lateral positioning is not reliant on lane markings. Collisions potentially avoided by AES occurred on roads with sufficient escape zones and road friction.
Results: The study shows that ELK systems with enhanced lateral positioning could potentially avoid 33 - 45 (36 - 49%) out of 91 head-on and single car crashes resulting in passenger car occupant fatality, which corresponds to a further 18% (5/28) compared to traditional lane support (LDW/LKA) without enhanced lateral positioning. The improved lane keeping addresses crashes involving absent or nonvisible lane markings that are covered by snow. Furthermore, the study shows that the evasive steering features of AES systems with enhanced lateral positioning could potentially prevent 28 (54%) out of 52 collisions resulting in passenger car occupant fatalities (i.e., head-on, intersection, rear-end, overtaking, and animal collision). Additionally, AES with enhanced lateral positioning could potentially prevent 16 (31%) out of 51 collisions between motor vehicles and vulnerable road users resulting in fatally injured pedestrians, cyclists or moped users. The total potential safety benefits of AES include both lane keeping and evasive steering features including lane escaping. The study identified that the total number of crashes potentially avoided by AES corresponds to 42% out of all crashes resulting in passenger car occupant fatalities ( n  = 48/114).
Conclusions: This is a first attempt to identify and quantify the increase in potential safety benefits, based on the assumption that robust lateral vehicle positioning has been applied to lane keeping as well as lane escaping. In addition to the potentially increased number of prevented crashes compared to traditional lane support, a robust lateral positioning system may have the potential to improve the redundancy in positioning systems. Previous research suggests several techniques to improve lateral vehicle positioning. However, further research is required, including testing for implementation of adequately improved lateral vehicle awareness to establish which techniques are appropriate.