When Do Teens Choose Distraction? Assessing Environmental Influence on Secondary Task Initiation to Understand Elevated Teen Crash Risk

Abstract

Secondary task engagement is disproportionately associated with crashes and near-crashes for novice drivers relative to any other age group, compounding an already substantial overrepresentation of young drivers in motor vehicle crashes, which remain the leading cause of death among adolescents in the United States. Why the association is so much stronger for this group is not fully understood. Prior research has documented how often teens engage in secondary tasks and which tasks are most dangerous, but has largely overlooked a contextual dimension: when teens choose to engage, and whether they adjust that engagement to the demands of the driving environment or not, thus contributing to their disproportionate crash risk. The present study examined whether teen (16-17), young adult (18-24), and adult (25-59) drivers differ in how they modulate general and visual-manual secondary task engagement across levels of environmental driving demand, defined by traffic density (level of service) and relation to junctions. Using naturalistic driving data from the Supervised Practice Driving Study and the Second Strategic Highway Research Program Naturalistic Driving Study, generalized linear mixed models were estimated separately for baseline driving and for safety-critical events (crashes and near-crashes). During baseline driving, teen self-regulation was largely intact: teens reduced engagement near junctions and increased engagement with higher traffic density just as adults did, differing only in that they engaged in the riskiest tasks at higher rates under low-demand conditions. During safety-critical events, however, this similarity disappeared. Near junctions, adults reduced engagement almost entirely while teens did not, with predicted general task engagement at high junction demand of 25.2% for teens compared to 0.7% for adults, and in dense traffic teen engagement rose sharply while adult engagement stayed flat, reaching 53.2% for visual-manual tasks compared to 5.7% for adults. These findings indicate that elevated teen crash risk is concentrated in high-demand, safety-critical moments because teen drivers fail to withhold engagement precisely when the driving environment becomes most lethal.