Quantification Metrics and Analysis of Human Factor, Workload, and Road Infrastructure

Abstract

This paper describes how human factors (HF) and user workload (WL) can be used by highway designers and traffic engineers to quantify the potential safety of sections of highway. Users’ WL is a quantitative measure of HF. Both HF and WL are used successfully in other fields, such as aviation when pilots have difficulty in using instruments and in touch-down before the start or end of the runway. The traditional highway approach of gauging success is by counting crashes. But with fatalities exceeding 30,000 a year for more than 20 years, the time is right for a new method of analysis. The author has integrated specific WL metrics into a simplified example to aid designers, traffic engineers, and safety analysts in assessing user problems before building new projects or road upgrades. The example uses static and dynamic WL and alternating renewal (AR) metrics (not used by others) to quantify user WL in highway segments for the purpose of illustrating the variation of design and operational safety conditions. The example can be easily modified when new metrics are created, and it illustrates the use of WL and its associated highway safety implications. In short, the approach is based on common sense with trained engineering experience and logic integrated into data-driven safety analyses. The example is a continuation of an earlier FHWA research study illustrating the application of road safety audits and the Interactive Highway Safety Design Model (IHSDM). The IHSDM, Excel, and Google Earth were used because no funding was available for on-road data collection.