Data and R Code for research paper
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Worldwide, more than one million people die on the roads each year. A third of these fatal accidents are attributed to speeding, with properties of the individual driver and the environment regarded as key contributing factors. We examine real-world speeding behavior and its interaction with illuminance, an environmental property defined as the luminous flux incident on a surface. Drawing on an analysis of 1.2 million vehicle movements, we show that reduced illuminance levels are associated with increased speeding. This relationship persists when we control for factors known to influence speeding (e.g., fluctuations in traffic volume) and consider proxies of illuminance (e.g., sight distance). Our findings add to a long-standing debate about how the quality of visual conditions affects drivers’ speed perception and driving speed. Policy makers can intervene by educating drivers about the inverse illuminance‒speeding relationship and by testing how improved vehicle headlights and smart road lighting can attenuate speeding.

General Information

This repository contains data and code collected by the Traffic division of the City of Zurich, Switzerland and the Swiss Federal Office of Meteorology and Climatology. The data were combined and analyzed by Michael Schulte-Mecklenbeck and Emanuel de Bellis. They are published under the GNU General Public License (version 3).


The connected paper is under review at Plos One and can be cited as follows:

De Bellis, E., Schulte-Mecklenbeck, M., Brucks, W., Herrmann, A., & Hertwig, R. (revise and resubmit). Blind haste: When light goes down, speeding goes up. Plos One.


We thank the Traffic Division of the City of Zurich for providing the speed measurements; Kevin Brooks, Karl Gegenfurtner, Jack Loomis, Fred Owens, Timothy Pleskac, and Paolo Pretto for comments on an earlier version of the manuscript; and Susannah Goss for editing the manuscript.