This document defines key terms and concepts for relating effects of driver distraction on driving performance, physiological indicators, subjective assessments, or combinations thereof to effects of driver distraction on crash involvement. These concepts are intended to contribute to methodologies for assessing driver distraction metrics in terms of their reliability, repeatability, bias, and predictive or descriptive validity and distraction evaluation procedures in terms of their real-world representativeness. The actual specification of such a methodology is outside the scope of the present document. While the focus is on driver distraction evaluation for technology evaluations and driver activities, the concepts described herein may be applicable also to other forms of driving performance evaluation. The intended users of the document are practitioners in the industry, academia and other organizations with an interest in driving performance assessment and road safety.
Driver distraction remains one of the key factors behind road crashes. There are many existing metrics and procedures for experimental evaluation of driver distraction, several of which have been specified in international standards and/or regional guidelines. The objects of analysis in experimental driver distraction assessment are typically specific driver activities and technologies used while driving. Such assessments make use of a wide variety of measures including measures of driving performance, eye glance behavior, response time, object and event detection, physiological status, subjective assessment, observer rating, and combinations thereof. These are generally obtained with procedures and apparatus that vary widely in terms of their fidelity to real-world driving and actual driver activities. The representativeness of such experimental or clinical evaluations may be quite low if they are not carefully tuned with respect to driver orientation, driver discretion or compensatory actions, task content, technology fidelity, driving scenarios, demand characteristics of the experimental setting, and exposures to simulated hazards or surprise events. Thus, a key issue is the often unclear relation between experimentally measured effects of driver distraction and actual crash involvement. This makes it difficult for human factors practitioners to use the results from distraction evaluation methods to inform decisions intended to improve road safety. Because of this, there is a need for a rigorous methodology based on precise terms and concepts that can be used to establish the relation between driver distraction measures and metrics obtained from experimental studies or clinical evaluation and distraction effects on real-world crash involvement.