Examination of Limitations Associated with Observing Driver Distraction

Studies that use direct observation to investigate drivers’ cell phone use have been conducted by NHTSA since 2002. The limitations of these studies were identified in a naturalistic driving study conducted at the University of Michigan. In direct observation studies of drivers’ cell phone use, observations are typically conducted at intersections, providing the observer with enough time to accurately observe the behavior but limiting data to one location along the roadway. This may be a limitation of large-scale observation usage studies, which, in turn, translates into a research hypothesis that when stopped at intersections, drivers use their cell phones more frequently. Through a combination of in-field observers and video data collection, more than 3,500 vehicles were observed to determine the difference in cell phone use between drivers upstream and those at the intersection. Signalized intersections were found to have a higher rate of text messaging cell phone use, with the highest percentage observed at red lights. Drivers’ text messaging rates increase with the amount of time spent in stopped conditions, such as red lights. The presence of an observer was also found to have an insignificant impact on drivers’ cell phone use. Effective observation of drivers’ cell phone use is essential for understanding the magnitude of the problem and measuring the effectiveness of campaigns. This study confirms the current methods used while providing recommendations on ways to improve the data quality of future observations.