Assessing in-vehicle secondary tasks with the NHTSA visual-manual guidelines Occlusion method

Abstract

The NHTSA Visual-Manual Distraction Guidelines propose two methods for evaluating which in-vehicle tasks should be allowed while driving. Of these, previous studies have shown that the Eye Glance measurement using Driving Simulator method (EGDS) has low reliability. This study therefore explored if the other proposed method, Occlusion Testing, provides a better alternative. Occlusion testing did indeed show more robust performance than EGDS. It also was more permissive, i.e., tasks that failed with EGDS passed with Occlusion. Furthermore, results indicate that for many tasks, Occlusion testing can be replaced with a simpler step count method. Two drawbacks were also identified. First, tasks requiring longer system search times are systematically allowed fewer interaction steps for completion. Second, test outcomes are highly dependent on participant instructions. Participants who perceive the evaluation as an individual test use more effort and develop optimization strategies, which means complex tasks that normally would fail will pass.