Evidence that cellular telephone conversations hinder driving performance is plentiful. However, why they should be more dangerous than passenger conversations has not been adequately explored. A passenger's ability to share situation awareness with the driver may reduce the negative effects of conversation but studies have not controlled for the effect of cellular telephone transmission. Unexpectedly, simulated driving performance was worst with a normal passenger and did not differ between blind passenger and no passenger conditions. The use of vacation as a naturalistic conversation topic and casual participant attitudes may have affected the results. Additional research is needed to further explore the differences between passenger and cellular telephone conversations to understand their effects on driving performance.
Automobile drivers engage in activities that could potentially detract from the attention needed to safely operate their vehicle. These activities may include listening to the radio, changing a compact disk or tape, eating, drinking, and conversing with passengers or on cellular telephones. Of particular interest has been the potential decrease in safety caused by cellular telephone use (see Horry & Wickens, 2006 for a metaanalysis). Investigations of naturally occurring traffic accidents revealed increased risks associated with cellular telephone usage (Redelmeier & Tibshirani, 1997; Violanti & Marshall, 1996). Determining how concurrent cellular telephone use affects driving performance may prompt the discovery of effective compensatory strategies or lead to legislative actions based upon research findings.
Talking on a cellular telephone while driving can increase the driver's reaction time (RT), reduce attention to events in the driving environment, and hinder course maintaining responses. Reactions to brake lights in car following tasks are slowed by secondary tasks (Levy, Pashler, & Boer, 2006), including cellular telephone conversations (Alm & Nilsson, 1995; Brookhuis, Consiglio, Driscoll, Witte, & Berg, 2003; De Vries & De Waard, 1991; Strayer, Drews, & Johnston, 2003; Strayer & Johnston, 2001). Drivers also tend to be more likely to miss cues to which they should respond when they are engaged in a cellular telephone conversation (McKnight & McKnight, 1993; Strayer & Johnston, 2001), and the effect is greatest when the conversation task is more difficult (McKnight & McKnight, 1993). Drivers also check their mirrors less often (Brookhuis et al., 1991) and are less likely to remember objects they see during the course of their drive (Strayer, et al., 2003), even when they look directly at those objects (Strayer, Cooper, & Drews, 2004). Other changes in the environment also are less likely to be noticed (McCarley et al., 2004) and drivers are more likely to miss a turn (Drews, Pasupathi, & Strayer, 2004) when engaged in a cellular telephone conversation. The drivers' ability to keep the vehicle traveling on the appropriate path also can be affected by cellular telephone use, especially when the driving task is difficult (Briem & Hedman, 1995; Strayer & Johnston, 2001). In different studies listening-only conditions have benefited driving performance (Brown, 1965), not affected performance (Consiglio et al., 2003; McCarley et al., 2004; Strayer & Johnston, 2001), and negatively affected performance (Kubose, Bock, Dell, Garnsey, Kramer, & Mayhugh, 2006; Jancke, Musial, Vogt, & Kalveram, 1994).
Performance deficits in driving performance during concurrent cellular telephone use are partially due to the physical manipulation of the equipment. When placing or receiving a call on a cellular telephone, users are required to manipulate the telephone in some way. Radio tuning can be similar to placing a cellular telephone call, in that both tasks require the physical manipulation of controls away from the steering wheel. …