Safety-related Variable Message Signs in Traffic Control applications

Traffic Management Systems are used for propagating information from a Higher Order Control Unit (HOCU) to the traffic participant. In today’s systems the user interface to the traffic participant is provided by actuators such as a Variable Message Sign (VMS). Information can be either non-safety-critical (e.g., traveller information, route information, congestion warning) or safety-critical (e.g., lane-control signs, variable speed-limit signs). Latest national and international standards prove the trend towards an increased demand for safety in such devices. These safety requirements need distinct measures in hardware as well as software. This paper presents a general approach to a safety-related VMS integrated in a traffic management system according to the standards EN 50556 and VDE 0832.