The causal effect of wrong-hand drive vehicles on road safety

Roesel, Felix · 2017 · OpenAlex-citations

DOI: 10.1016/j.ecotra.2017.10.002

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Summary

This paper investigates the causal impact of wrong-hand drive vehicles on road safety, addressing a significant policy debate in countries where vehicle configuration does not align with traffic direction. The motivation stems from the rising prevalence of imported right-hand drive (RHD) vehicles in right-hand traffic emerging markets, such as Georgia, Kyrgyzstan, and Russia, driven by lower prices. While descriptive statistics suggest higher accident rates for mismatched vehicles, prior studies lacked causal evidence due to endogeneity issues. The author utilizes Sweden’s 1967 switch from left-hand to right-hand traffic as a natural experiment. Before the switch, Sweden drove on the left but predominantly used left-hand drive (LHD) vehicles due to trade and consumer preferences, creating a widespread mismatch. After 1967, Sweden aligned with continental Europe’s right-hand traffic while retaining LHD vehicles, effectively eliminating the mismatch. To identify the causal effect, the study employs a modified “backward” synthetic control method. Because no other country historically exhibited widespread wrong-hand drive usage, the author constructs a counterfactual “Synthetic Sweden” by matching on post-1967 accident trends, when Sweden and other European countries shared the same traffic and vehicle configuration. The donor pool consists of 13 European countries, with weights derived to minimize the Root Mean Square Percentage Error of road fatalities between 1968 and 2012. The analysis uses data from 1953 to 2012, controlling for GDP, population density, seatbelt legislation, and speed limits. Robustness checks include placebo tests on other countries and validation via OLS and weighted least squares difference-in-differences estimations. The results indicate that the switch to right-hand traffic reduced road fatality, injury, and accident risks in Sweden by approximately 30%. Specifically, pre-1967 fatality rates in Sweden were 41 fatalities per million capita higher than the synthetic counterfactual. This reduction translates to an estimated 4,000 lives saved between 1953 and 1966 had the switch occurred earlier. The findings remain robust when substituting fatalities with accidents or injuries and are not driven by concurrent policy changes, such as speed limit legislation or seatbelt mandates, which the author rules out through detailed sensitivity analyses. The study concludes that regulating wrong-hand drive vehicles significantly enhances road safety. The author extrapolates these findings to suggest that banning LHD vehicles in the UK or RHD vehicles in Kyrgyzstan could prevent hundreds of annual accidents and fatalities. While acknowledging political and economic resistance to such bans in emerging markets, the paper argues that the substantial safety benefits justify strict regulations or alternative solutions, such as changing traffic sides or mandating improved visibility technologies.

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• comparative international
• regulatory evaluation

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• Empirical Findings: crash risk outcomes