Traffic Safety Potential and Effectiveness of Lane Keeping Support
Doctoral thesis, 2020

In the road transport system, crashes due to lane departure account for a large proportion of the most severe crashes that passenger car occupants are exposed to. While Electronic Stability Control (ESC) effectively prevents lane departure due to loss of control, lane departure due to unintentional drifting has not been addressed to the same extent. This thesis is based on four papers providing knowledge of lane keeping support integrated in vehicles and road infrastructure. More precise, the safety potential and effectiveness of Lane Departure Warning (LDW) was studied as well as the effectiveness of centreline rumble strips (CLRS). Also, the potential safety benefits of Emergency Lane Keeping (ELK) and Autonomous Emergency Steering (AES) with enhanced lateral vehicle positioning were studied. Reviewing real-world in-depth data of 138 fatal crashes in Sweden 2010 and 114 in 2017, the results show that virtually half of the single vehicle and head-on crashes involved unintentional drift-out-of-lane, where LDW, ELK and AES should have had the potential to prevent the majority of these crashes. Estimating the effectiveness of LDW by analysing 1,853 police reported real-world injury crashes during 2007‒2015 extracted from the Swedish Traffic Accident Data Acquisition (STRADA) database and applying the induced exposure method, it was found that LDW halved the risk of being in a head-on or single passenger car injury crash. Posted speed limits were at 70 km/h and above and the road surface had not been covered by ice or snow. Estimating the effectiveness of CLRS by merging STRADA injury crashes during 2011‒2016 involving 7,490 cars with the National Road Database in Sweden (NVDB) and applying the induced exposure method, the results show a reduction in head-on and single car crashes. Crashes involving drift-out-of-lane to the left were reduced by 40% (19‒56%) for ESC-equipped cars, and by 29% (11‒44%) for cars without ESC. It could be confirmed that in-depth data with high detail can provide benefits in evaluating future road safety features. Furthermore, it was found that merging STRADA, NVDB and individual vehicle equipment data has significant methodological benefits in combination with data efficient methods such as the induced exposure approach.

LDW provided by the vehicle industry and detectable lane markings provided by road authorities are parts of a system showing significant traffic safety benefits. As both components are dependent on each other, this makes safety the responsibility of both road authorities and the vehicle industry. Not only do LDW and CLRS complement each other, they also complement ESC and are able to avoid critical situations. LDW and CLRS are two of the most important traffic safety features for the foreseeable future, in which the share of unintentional lane drifting crashes is expected to increase. ELK will in the near future be mandatory for new cars, hereby detectable lanes and lateral vehicle position awareness will be even more important. Future research should focus on increasing the synergy between car and infrastructure interventions, holistically and systematically utilising the integrated safety chain.

Traffic Safety


Lane keeping



Lateral positioning



Opponent: Prof. Dipl.-Ing. Klaus Kompass, BMW Group, Germany


Simon Sternlund

Chalmers, Mechanics and Maritime Sciences (M2), Vehicle Engineering and Autonomous Systems

This thesis shows that if technology alerting drivers unintentionally drifting out of lane is installed in all cars in the Swedish car fleet, approximately 30 lives would be saved besides the significant number of serious injuries that would be avoided each year in Swedish traffic. The in-vehicle support system, Lane Departure Warning, has been investigated through in-depth studies of fatal crashes as well as analyses based on Swedish national traffic crash data of injury crashes including 1,850 Volvo cars. Lane Departure Warning detects the travel lane by its lane markings and road edge lines, and issues a warning through sound or vibration via the steering wheel or seat to prevent unintentional drift-out-of-lane, typically due to driver drowsiness, distraction, or inattention. Approximately half of all fatal head-on and single car crashes commence in unintentional lane drifting. In the other half of the crashes, critical situations involve loss of control/skidding, while a small number of crashes commencing in drifting result in loss of control. While Electronic Stability Control systems are effective in supporting the driver in avoiding loss of control, the Lane Departure Warning system supports the driver in avoiding lane drifting. Both systems are crucial since they complement each other.

This thesis also shows that rumble strips positioned in the centre of the road represent a traffic safety measure effectively supporting the driver in avoiding unintentional lane drifting. The analysis indicates that Electronic Stability Control systems can enhance the effectiveness of centreline rumble strips. This synergetic effect can arise when the driver is in a position to react to the warning received from the centreline rumble strips and safely revert back to the lane without loosing control of the car. This thesis shows that implementing centreline rumble strips is an effective measure for reducing the amount of injury crashes on roads without median barrier since replacing the car fleet with newer cars equipped with Lane Departure Warning is time consuming.

The common denominator for Lane Departure Warning systems and centreline rumble strips is to support keeping the car’s lateral position. This thesis shows that robust lateral vehicle positioning with enhanced precision is of significant value for future in-vehicle safety systems relying on automatic steering in critical situations, such as Emergency Lane Keeping and Autonomous Emergency Steering in order to avoid crashes and consequently save lives.

Driving Forces

Sustainable development

Areas of Advance


Subject Categories

Transport Systems and Logistics

Infrastructure Engineering

Vehicle Engineering



Doktorsavhandlingar vid Chalmers tekniska högskola. Ny serie: 4796




Opponent: Prof. Dipl.-Ing. Klaus Kompass, BMW Group, Germany

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