Effects of Looming Auditory FCW on Brake Reaction Time under Conditions of Distraction

In 2013, 1.8 million US drivers were responsible for rear-end collisions with other vehicles (NHTSA 2014), for which driver distraction has been identified as the main factor (Campbell, Smith & Najm, 2003; Knipling, Mironer, Hendricks, Tijerina, Everson, Allen & Wilson 1993; Wang, Knipling & Goodman, 1996). The ubiquity of cell phones and their use behind the wheel has played a major role in distracting these drivers. To mitigate this, some manufacturers are equipping vehicles with forward collision warning (FCW) systems.

Generally, warnings that are perceived as being urgent produce lower response times. One technique for increasing perceived urgency of a warning is called looming, where the signal increases in or more dimensions over time. Looming warning signals have been shown to produce low response times, likely because the recipient perceives the signal as a potential approaching threat, prompting defensive reactions (Graziano and Cooke, 2006).

The present study evaluates the effect of veridical (intensity increases at the rate of closure with the lead vehicle) and high urgency (intensity increases at a rate of Time to Collision minus 0.5 seconds) looming FCW, as well as a static FCW, on drivers’ brake reaction times in the presence of a secondary texting task. Participants’ brake reaction times were recorded as they followed a lead car in a driving simulator, encountering multiple sudden-braking events across the five conditions (a control condition as well as four counterbalanced conditions using a secondary texting task). In the four conditions with a secondary task, participants received no FCW, static FCW, veridical FCW, and high-urgency FCW, respectively. Performance data was analyzed using a repeated measures ANOVA, and a series of pairwise comparisons were then made using Bonferroni corrected pairwise t-tests.

The presence of a visually and manually distracting secondary task (texting) seems to diminish the performance of the looming signals as compared to previous studies that did not use a distraction component. While looming FCW do seem to effectively lower BRTs when the driver is distracted, it is recommended that further research investigate the relationship between secondary task types and their respective levels of distraction, and the effectiveness of auditory looming FCW.