The tendency of drivers to pass other vehicles Hillel Bar-Gera * , David Shinar Department of Industrial Engineering and Management, Ben-Gurion University, P.O. Box 653, Beer-Sheva 84105, Israel Received 30 December 2004; received in revised form 27 May 2005; accepted 28 June 2005 Abstract The purpose of this study was to assess the speed differential threshold—if there is one—at which drivers decide to pass a lead vehicle. Drivers in a simulator encountered vehicles in front that were programmed to travel at speeds that were similar, slightly below, or even slightly above the driversÕ own speed. The study involved a total of 152 such passing opportunities. In almost all of the encounters with slower vehicles (traveling at speeds slower than 3 km/h of the driver) they passed them, and in two thirds of the encounters when the lead vehicles were moving at their speed they passed them too. Most surprising was that in 50% of the encounters drivers passed the lead vehicle when it was traveling faster than their average speed. In these situations drivers actually increased their own speed substantially to accomplish the passing maneuver, despite the fact that not passing the lead vehicle would not have caused any delays. The tendency to pass appears to be related to the driversÕ own speed variability: the more variable the driverÕs speed the more likely he or she was to pass the vehicle ahead even when its speed was greater than their average speed. The results are interpreted in terms of (a) driver aggression, and (b) association of car following with added effort, attention overload, or risk. The latter explanation implies that the tendency to pass vehicles may be reduced with the introduction of in-vehicle technologies such as adaptive cruise control. Ó 2005 Elsevier Ltd. All rights reserved. Keywords: Driving behavior; Passing; Road safety 1369-8478/$ - see front matter Ó 2005 Elsevier Ltd. All rights reserved. doi:10.1016/j.trf.2005.06.001 * Corresponding author. Tel.: +972 8 6461398; fax: +972 8 6472958. E-mail address: bargera@bgu.ac.il (H. Bar-Gera). www.elsevier.com/locate/trf Transportation Research Part F 8 (2005) 429–439