Ten years of compatibility testing motorway communications interfaces

Integrated systems are key to a successful integrated road transport policy. However, as the diversity and complexity of systems increases, the probability of compatibility problems rises dramatically. These problems may include: poor reliability of the systems in the field; procurement agencies become unnecessarily constrained; high cost of field upgrades if something is found to be wrong in the field; high risk when adding additional equipment later on. The UK has addressed this by developing protocols for the interchange of real time information known as National Motorway Communication System (NMCS). The protocols have used, where possible, existing national and international standards. The on-going management of the protocols has two parts: a well maintained specification of NMCS and a rigorous compatibility testing regime to type-certify equipment before its installation the field. The approach has balanced the need for compatibility with open supplier competition and technological innovation and diversity, leading to reduced costs and improved functionality. This paper describes; the role of NMCS on the UK highways; the specification management processes for NMCS and related equipment; the approach taken to compatibility testing both in technical and organisational terms. In particular, how it can help in the early identification of problems; some examples of the less obvious compatibility issues discovered during the last ten years; the gains achieved, not only in reliability, a key reason for compatibility testing, but also in costs and technological diversity.