This SAE Recommended Practice defines key terms and metrics applied in the analysis of video based driver eye glance behavior. It can be applied in environments from real world trials to laboratory based driving simulator studies evaluating Transport Information and Control Systems (TICS). The procedures described in this document could also apply to more general assessments of driver visual behavior in the absence of TICS or other advanced display and control systems associated with Intelligent Transportation Systems (ITS). Driver workload studies, design of traffic control devices and roadways, modality interference from use of cell phones, mirror redesign, situational awareness, and the effects of driver stress from sleep loss and trip delays are just a few of the studies that would benefit from a standard practice for measuring visual allocation. The metrics and definitions described as follows are intended to assist development of a common source of reference for driver visual behavior data. With specification of independent variables, data collated and analyzed from this document allow comparisons to be performed across different device evaluations and experimental scenarios. It should be noted that the following definitions and measures would also apply to eye movement techniques. This document does not include the use of "head-up" displays. This document has been developed under the supervision of the SAE Safety and Human Factors Committee.

Introduction

Vision provides the primary source of information available to the driver. Information is gathered by looking at objects and events, which in turn enables decision-making, control, and navigation of the vehicle in the road traffic environment. Assessment of driver visual behavior (eye glance behavior) provides a method to quantify the driver's visual allocation to the roadway, traffic control devices, in-vehicle information sources, controls and mirrors and as such can be a useful tool in many ergonomic studies of the driver. These would include evaluation of the visual demands of in-vehicle information devices, assessment of visual distraction, driver fatigue, workload, individual differences (e.g., novice versus expert) and basic studies of visual allocation in driving.

TICS and other advanced display and control systems associated with ITS can present a range of driver related information. If these visual displays have associated controls (e.g., to select a zoom level or menu option), then the associated hand-controlled activities may also be visually guided and become part of the visual demand associated with a display application. For this reason, it may be important to consider not only the visual behavior in relation to information display, but also the duration and frequency of glances associated with driver control actions.

In the past, comparisons between separate evaluations of specific vehicle systems in different test environments have been made more difficult by dissimilar approaches in experimental techniques, operational definitions and analysis methods.

This document has been developed to give guidance on the terms and measures relating to the collection and analysis of driver visual behavior data. This approach aims to assess how drivers respond to vehicle and equipment design, the road environment, or other driver related tasks in both real and simulated road conditions. It is based on the assumption that efficient processing of visual information is necessary to the safe performance of the driving task in a given driving situation.

Practical assessments of drivers in real or simulated environments are conducted to quantify the allocation of visual behavior to specified targets. It may be quantified by the location, duration, and frequency of glances to a specified target in the visual scene. This approach often employs commonly available video-recording equipment. However, it does not preclude the use of more sophisticated technologies such as eye movement techniques, which may elicit additional driver visual behavior information. See Appendix A for a general discussion on capture techniques for video based eye glance data.