Early deployments of standards have revealed some differences of opinion within the transportation industry as to what constitutes interoperability and how standards may be used to achieve it. Such misunderstandings have occasionally led to early deployments of systems that do not have the expected interoperability. This paper discusses issues that limit or restrict interoperability in deploying early versions of standards, and the solutions that are currently in development. While some ITS standards are not yet complete, they are well on the way to providing expected interoperability benefits