The effect on cyclist safety of daytime running lights
DOI:
https://doi.org/10.55329/qwqe8132Keywords:
cyclist accidents, randomised controlled trial, road safety, vulnerable road usersAbstract
On average, Danes cycle 1.3 kilometres per person per day. However, according to emergency department statistics, each year more than 16,000 cyclists are injured in Denmark. In an effort to improve cyclist safety we tested the effect of daytime running lights (DRL) on the number of cyclist accidents. Using a randomised controlled trial design, 5,380 voluntary cyclist participants were randomly assigned to a test group (using DRL continuously for one year) or a control group (using their usual light routine for one year). Participants were provided with accident surveys once each month. A total of 230 accidents were reported: 121 in the test group and 109 in the control group. Most accidents were multi-party accidents (MPAs), took place in winter and in daylight. Safety effect of DRL was estimated as incidence rate ratio (IRR) between the test and control group. The incidence rate is the number of accidents per person-month. Reports of single-bicycle accidents (SBAs) in daylight were used to correct for potential report bias following Madsen et al. (2013). For multiparty personal injury accidents (PIAs), the corrected overall effect of DRL was a 25% risk reduction. The effect was insignificant. For all multiparty accidents, the corrected overall effect of DRL was an insignificant 30% risk reduction. For multiparty accidents in the dark, the effect of DRL was a significant 71% risk reduction. This is surprising, since it would be fair to assume that DRL primarily would affects accidents in daylight, where cyclists typically do not have lights on. The finding is likely due to participants in the test group having much better lighting at night than participants in the control group—or simply because some cyclists in the control group non-compliantly with the Road Traffic Act did not use lights at night during the experiment.
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Author Biographies
Tove Hels, Aalborg University, Denmark
Tove Hels holds a PhD from University of Copenhagen. She works as an associate professor in the Traffic Research Group at Aalborg University. Tove's research interests include various aspects of road safety—such as vulnerable road users, randomized controlled trials, driving under the influence of alcohol and other psychoactive substances, speed and risk. She is co-founder of the think tank ‘Trafiksikkerhed’ (‘Road Safety’) in Denmark (www.trafiksikkerhed.dk).
CRediT contribution: Formal analysis, Validation, Visualization, Writing—original draft.
Tanja Kidholm Osmann Madsen, Aalborg University, Denmark
Tanja Kidholm Osmann Madsen received her PhD in road safety at Aalborg University (AAU). She is associate professor in the Traffic Research Group and works within the areas of transport planning and transport engineering with a particular focus on road safety. Her current research focuses on the safety of cyclists, underreporting of accidents and alternative data sources, studied through large-scale randomized controlled trials and survey research in collaboration with road authorities and stakeholders.
CRediT contribution: Conceptualization, Data curation, Formal analysis, Investigation, Writing—review & editing.
Michelle Cederstrøm Christensen, Aalborg University, Denmark
Michelle Cederstrøm Christensen holds an MSc in Politics and Administration with a specialization in leadership and governance. She was part of the group until graduating in 2023. Her academic interests lie in public sector organization, leadership, and administrative analysis. She currently works with organizational development and strategic analysis at Aalborg University Hospital.
CRediT contribution: Data curation, Investigation, Visualization.
Anders Brogaard Tallaksen, Aalborg University, Denmark
Anders Brogaard Tallaksen holds an MSc in transport engineering and was affiliated with the Traffic Research Group at Aalborg University as an assistant during his studies until graduating in 2023. His master's thesis investigated the characteristics of single vulnerable road user accidents. He is interested in the potential of technology to improve traffic safety.
CRediT contribution: Data curation, Investigation, Visualization.
Harry Lahrmann, Aalborg University, Denmark
Harry Lahrmann graduated from the Technical University of Denmark but has been affiliated with Aalborg University since 1987, first as an assistant professor and then as an associate professor. He is also the founder of the Traffic Research Group. His research areas are transport planning and traffic engineering, with a focus on traffic safety and intelligent transport systems. Over the years, he has authored over 200 scientific conference papers, articles and books within these areas with his colleagues.
CRediT contribution: Conceptualization, Funding acquisition, Methodology, Project administration, Writing—review & editing.
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Copyright (c) 2025 Tove Hels, Tanja Kidholm Osmann Madsen, Michelle Cederstrøm Christensen, Anders Brogaard Tallaksen, Harry Lahrmann
This work is licensed under a Creative Commons Attribution 4.0 International License.
