Use of a driving simulator to evaluate and optimize factors affecting understandability of variable message signs

Variable message signs often require multiple phases in order to convey a complete message to drivers. The dual necessity of maximizing the understandability of these messages and minimizing the time required to convey these messages to the driver is an obvious one, especially during traffic incident management. The objectives of the research were to analyze the factors that affect the readability and comprehension of multiple phase messages presented on variable message signs during a simulated driving task, and to identify the levels of the factors that maximize driver performance. Specifically, a mid-level driving simulator was used to study the joint effect on driver performance of. obstructions of variable message signs by traffic or road geometry; the sequence in which the individual phases of a two phase message are presented to the driver; the message content; and the number and direction of lane changes required by the driver based on the message presented. The above factors were evaluated for two types of message duration (i.e., the duration for which each phase of a two phase message is presented), one based on existing recommendations and the other based on a proposed duration. Driver performance was evaluated for both durations. Clear advantages were obtained when a message was presented for a relatively short duration and repeated twice during the time in which it was visible. (C) 2004 Elsevier Ltd. All rights reserved.