Secondary task engagement is one of the main causes of traffic accidents. In order to determine the crash risk, the prevalence of secondary task engagement has been examined in a variety of surveys and observational studies. However, the data in surveys and questionnaires may be subject to memory biases and observational studies show deficits in assessing subjectively perceived distraction. Therefore, the aim of this project was first of all to investigate prevalence of secondary tasks while driving for a representative sample of German drivers. Secondly, the study examines the validity of the survey methodology. In the first study, a nationwide representative survey on secondary task engagement by means of face-to-face interviews was conducted with 1.072 car drivers in four different cities in Germany. Quota sampling based on the frequency of German driver´s license holders was applied in order to achieve a representative sample with respect to age and gender. On average, the drivers performed two secondary tasks in the last 30 minutes of their trip. The most frequently mentioned tasks were interacting with passengers, operating vehiclerelated equipment, and self-initiated actions (e.g. self-talk). In the second sub-study, a validation of the survey methodology was conducted with a naturalistic driving study (NDS). Therefore, a comparison of video and survey data was undertaken. The analysis included data of 76 drivers. Whereas accordance between survey and video data was rather high for consciously performed and sporadic activities (e.g. making phone calls, reading / writing text messages) it was relatively low for recurrent unconscious activities (e.g., operation of vehicle-related equipment, personal hygiene, changing clothes / glasses). From the results of the validation it can be concluded that surveys are a suitable and valuable method to gather information about prevalences of more consciously performed and sporadic secondary tasks. (Author/publisher)
Samenvatting