This document will provide specifications for a “Concept of Operations (CONOPS) for the introduction and maintenance of a “Mixed Vendor Environment” (MVE) in the domain of urban-ITS. Structured as: PART I "Context and issues to be addressed" Describing the context, background, objective of the MVE Guide, and the architectural context. PART II "Work concepts" Examines aspects of system design and architecture , and presents the basic knowledge required for the application of Part III. PART III "Practice" Provides system design and procurement on three levels against the background of a procedure model. - user level - conceptual explanation - examples. PART IV "Outlook" Specifies guidance and requirements for the application of MVE for future business.