Objective: Electronic Stability Control (ESC) and Lane Departure Warning (LDW) are in-vehicle safety systems that complement each other. While the implementation of on-board lane support systems in traffic is still limited and the majority of the traffic volume is made up by ESC-equipped cars, the effectiveness of centerline rumble strips (CLRS) for ESC-equipped cars need to be quantified. The aim of the present study is to estimate the effectiveness of CLRS on two-lane carriageways in Sweden, on injury accident risk for cars equipped with ESC and cars without ESC. Methods: Police reported injury crashes during 2011-2016 were extracted from the Swedish Traffic Accident Data Acquisition (STRADA) database and merged with the National Road Database (NVDB) containing information regarding road design and road use parameters. The analysis includes crashes on two-lane carriageways in Sweden with a width of at least seven meters in dry and wet road conditions, that is, road surface not covered by ice or snow. The crashes involved a total of 7,490 cars with injured drivers, where 39% of the cars were equipped with ESC. The effectiveness estimates were calculated for injured drivers in ESC-equipped cars in crashes involving drift out of lane to the left, and posted speed limits of 80 and 90 km/h. The analysis was carried out by applying the induced exposure approach in which rates of cars involved in crashes sensitive and non-sensitive to CLRS were compared at sites with and without CLRS. In order to substantiate the evidence for causality, case and control rates of car model year and Seat Belt Reminder (SBR) fitment, driver age, driver gender, traffic volume, road width, speed limit and road surface condition were compared. Results: For ESC-equipped cars, the analysis showed a reduction in CLRS-sensitive crashes by 40% (19-56%, confidence interval [CI] 95%) where CLRS had been implemented, and a reduction by 29% (11-44%, CI 95%) for cars without ESC-equipment. Conclusions: Contemporary effectiveness estimates may have important implications for the short and medium-term national road safety management. CLRS remains an important countermeasure to consider for reducing the number of real-world injury crashes. From a systematic safety perspective, it is important to accentuate that CLRS and ESC essentially address different crash scenarios. Still, both CLRS and ESC have the potential to avoid crashes involving unintentional lane drifting resulting in loss of control. When the CLRS alerts a driver of unintentional lane drifting, the ESC can be essential in supporting the driver to safely veer back into the lane without loss of control. However, further analysis on the combined safety benefit of ESC and CLRS is required.
