The Relative Risks of Secondary Task Induced Driver Distraction 2008-21-0001

Driver distraction, defined here as engaging in a secondary task or activity that is not central to the primary task of driving, has been shown to be a contributing factor for many crashes. The secondary tasks and other activities in which drivers choose to engage while driving is also known to be highly varied, including very complex activities(e.g., text messaging on a cellular device) to very simple activities (e.g., selecting a radio preset).

Several important distinctions affect the relative risk of engaging in these tasks. Recent data from large-scale instrumented vehicle studies (i.e., “naturalistic” driving studies like the recently released “100 car study” (1)) have begun to provide data where the relative risk, in terms of crash and near crash involvement, can be directly assessed for differing secondary tasks. These data have provided some important insights into the features that create risk.

For example, these data have shown that engaging in a task that is at least “moderately complex” can significantly elevate crash/near crash risk compared to driving while performing no secondary tasks. A moderately complex task in this case is operationally defined as one where the driver must take their eyes off of the road in at most two glances to complete. However, the same data show that simple tasks, defined as requiring no more than a single glance or simple control manipulation to complete, do not significantly increase crash/near crash risk. It is important to note that simple tasks include those that require only “cognitive” attention, defined here as any task that does not require the driver to take their eyes off of the road or hands off of the wheel.

These results have significant implications for the design of driver-vehicle interfaces, as well as the need for future integration of nomadic devices into the driver-vehicle interface in a manner which will minimize crash risk.