As a result of Intelligent Transportation System (ITS) initiatives in the United States and abroad, a wide variety of in-vehicle information systems are being proposed and developed for use in heavy trucks and cars. Such systems can improve transport efficiency, driver satisfaction, and highway safety. However, these technologies must be designed such that their use does not distract the driver or otherwise interfere with the driving task. This interference is what is referred to by the term “driver workload” in this paper. What is needed is a workload assessment protocol that can be used to evaluate the safety impacts of in-vehicle systems and promote a driver-centered design.

In response to this need, a program of research was undertaken to develop a safety-relevant workload assessment protocol. This paper presents:​ a brief description of the resulting protocol document;​ approaches taken to establish the safety relevance of the measurement system;​ application of the protocol to cellular phone use and text message displays in heavy vehicles;​ and future directions.