Validity of Variable Message Sign Information: Is It Influenced by Drivers’ Short-Term Memory?

Abstract

Variable message signs (VMSs), as a key component of intelligent transportation systems, have been frequently used in the management of urban roads to provide drivers with real-time traffic information. Nevertheless, a lack of unified regulations for VMS design, makes it difficult to accurately determine the validity of VMS information. In practice, inappropriately designed VMSs (e.g., VMSs overloaded with information and long setting distances) are common. In this study, laboratory simulation trials were conducted to assess VMS information validity in relation to the short-term memory (STM) capacity of drivers. Specifically, drivers capacity to easily obtain and respond correctly to valid VMS information based on memorized target information. Sixty participants completed the trials and pre-/postquestionnaires. Subjective evaluation, dynamic information acquisition rate, accuracy, and memory reliability were analyzed to evaluate their relationship with VMS information validity. The results confirmed that STM considering the information demand rate significantly affected the validity of the VMS information. Information validity deteriorated as the information volume and VMS setting distance increased. Reasonable validity was found when memory reliability ranged between 0.85 and 1.5 and the information volume was no more than 90 bits, corresponding to a subjective evaluation of 1, an accuracy of at least 80%, and a suggested STM time of 43.46 s. These criteria would satisfy driver information demand and prevent information redundancy or wasting of resources. These findings provide a basis for determining the thresholds for VMS information to promote practical and user-friendly VMS designs on urban roads.