Do drivers reduce their speed when texting on highways? A replication study using European naturalistic driving data

Cell phone usage, especially texting while driving is common among drivers globally. Various experimental studies indicate that drivers compensate for the increased demand by reducing speed. However, naturalistic driving data analyses reveal only small changes in speed. For example, in an analysis of the SHRP 2 naturalistic driving data, only a small speed adjustment was identified when texting while driving on a free-flow interstate (Schneidereit et al., 2017). The present study's objective was to replicate these findings using European data. In addition, the study sought to determine the overall secondary task prevalence while highway driving. A total of 1000 randomly selected highway driving episodes were manually annotated. For the identified visual-manual cell phone interactions (further subsumed into "texting"), driving speed was compared between the 10 s before and 10 s after initiating (concluding) texting. We focused on free-flow driving episodes to minimize factors that could potentially confound drivers' speed choice, which resulted in 147 texting events. Drivers engaged in at least one secondary task in 57% of the annotated trip segments. In most events, drivers adjusted controls, used the cell phone and interacted with passengers. Moreover, speed adjustments while texting were found. Drivers reduced their speed by more than 2 km/h after initiating texting and regained their speed after concluding texting. These effects were greater than the ones found with the SHRP 2 data, indicating that European drivers self-regulate to a greater extent than US drivers. Reasons for this discrepancy (e.g., possible differences in road infrastructure) are discussed.