Accident Analysis and Prevention 38 (2006) 988–996 Assessing the effectiveness of “intuitive” vibrotactile warning signals in preventing front-to-rear-end collisions in a driving simulator Cristy Ho a,∗ , Nick Reed b , Charles Spence a a Department of Experimental Psychology, University of Oxford, South Parks Road, Oxford OX1 3UD, United Kingdom b Transport Research Laboratory, Crowthorne House, Nine Mile Ride, Wokingham, Berkshire RG40 3GA, United Kingdom Received 25 October 2005; received in revised form 20 January 2006; accepted 5 April 2006 Abstract This study was designed to investigate the possibility that driver responses to potential front-to-rear-end collision situations could be facilitated by implementing vibrotactile warning signals that indicate the likely direction of the potential collision. In a car following scenario in a driving simulator, participants drove along a rural road while trying to maintain a safe headway distance to the lead car using a visual distance display. Participants had to respond as quickly as possible to the sudden deceleration of the lead car which had its brake lights disabled, either with or without vibrotactile cues (presented in different experimental blocks). The results demonstrated significantly faster braking responses and larger safety margins when the vibrotactile warning signal was presented than when it was not. These findings demonstrate the effectiveness of vibrotactile cues in helping drivers to orient their spatial attention in the appropriate direction. Our results add to a growing body of empirical evidence highlighting the potential benefits of using “intuitive” vibrotactile in-car displays, in this case, to alert drivers to potential collisions and to provide time-critical directional information. © 2006 Elsevier Ltd. All rights reserved. Keywords: Vibrotactile; Warning signal; Intuitive; Directional; Car following; Front-to-rear-end collision 1. Introduction Driver inattention, meaning a lack of concentration, has been identified as one of the leading causes of car accidents, esti- mated to account for 26–56% of all road traffic accidents (see Gibson and Crooks, 1938; Treat et al., 1977; Wang et al., 1996). Importantly, the increasing provision of complex in-car tech- nologies means that drivers may become increasingly distracted in the years to come, thus making it likely that the problem of driver inattention will become worse (e.g. Ashley, 2001; Dukic et al., 2006; Lee et al., 2001; Patten et al., 2004). Consequently, sophisticated safety warning systems are now being developed in order to try and promote safe driving (e.g. Lee et al., 2004). In fact, the technology has now been developed to enable “intel- ligent” cars to detect dangerous road situations (e.g. adaptive radar cruise control systems), which in theory means that the car could potentially take control away from the driver and become ∗ Corresponding author. Tel.: +44 1865 271307; fax: +44 1865 310447. E-mail addresses: cristy.ho@psy.ox.ac.uk (C. Ho), nreed@trl.co.uk (N. Reed), charles.spence@psy.ox.ac.uk (C. Spence). autonomous (Knight, 2006). However, car manufacturers cur- rently prefer that the control of the car remains in the hands of the drivers owing to legal implications (see Hutton and Smith, 2005; Knight, 2006). Therefore, investigations into the design of optimal warning signals that can alert drivers to potential dangers are essential. One human sense that could potentially be utilized more in a driving environment is the sense of touch. The integration of touch into the traditional focus on vision and audition in automobile design is supported by robust neuropsychological research on the multisensory integration of sensory information (see Calvert et al., 2004; Spence and Driver, 2004). Given the high utilization of vision in driving (e.g. Sivak, 1996), it seems plausible to present certain information to the tactile sense when the visual channel is heavily loaded (or overloaded). The tactile sense has been demonstrated to be automatically alerting, inher- ently directional, private to the driver, and it has been argued that unlike vision, it cannot be “shut out” voluntarily (see Gilmer, 1960, 1961; see also Burnett and Porter, 2001; Campbell et al., 1996; Hennessy, 1966; Lee et al., 2004). Recent research has documented the feasibility of present- ing directional information to drivers via vibrotactile displays 0001-4575/$ – see front matter © 2006 Elsevier Ltd. All rights reserved. doi:10.1016/j.aap.2006.04.002