This paper describes how, in the road environment, the main functions of Intelligent Transport Systems (ITS) are to promote road safety and improve traffic flow via effective communications to drivers. Variable Message Signs (VMS) are currently one of the most powerful and widely implemented tools for this matter. These new road signs are flexible; a VMS can be on and off; serve different road functions (warn, regulate, advise); display different elements (pictograms, text, or both); and adopt different message formats. By displaying complex, real-time road information, VMS intend to contribute to a higher efficiency and integration on the road transport system. However, several drawbacks may appear, on the one hand, VMS normally operate on high-speed roads; displaying too much information may have negative effects (e.g., overload; distraction; anomalous reactions, e.g., drivers slowing down abruptly). On the other hand, even when the basic informative elements are on, some structural parameters must be adopted in order to preserve and ease regular interpretation of information on the part of drivers. The main goal of this paper is to offer some considerations and design recommendations for better use of VMS on the road. Although this paper focuses on road transport, many of the general issues addressed in the paper will also be relevant to new technologies for rail, aviation, maritime, and pedestrian signing.
Abstract