Lessons learned in interfacing dynamic message signs with a trunked radio system

The Nevada Department of Transportation (NDOT) and its Las Vegas area partners have identified a need for a freeway management system (FMS) to help manage traffic during fluctuating periods of vehicle demand on freeways and arterials, as well as provide enhanced incident response capabilities. The Freeway and Arterial System of Transportation (FAST) will combine the existing LVACTS (Las Vegas Area Computer Traffic System) with the new Freeway Management System (FMS, currently being designed) into one integrated system, maximizing mobility. A key component of the project will be dynamic trailblazer signs. The paper describes the purpose of dynamic trailblazer signs and the types of signs that were considered. It then discusses the communication media that were considered for the signs, and reasons for selecting an existing 800 MHz voice and data radio system for use with the signs. A program to test prospective sign vendors' compatibility with the radio system is described. Both an analog and digital means of communication were tested. Our experience with each sign vendor is discussed, and our team's lessons learned are presented. To date, six vendors have tested their equipment with the NDOT radio system, and four are prequalified.