This document provides 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 — Describes the context, background, objective of the MVE Guide, and describes the architectural context. — PART II work concepts — Aspects of system design and architecture are examined and the basic knowledge required for the application of Part III are presented. — PART III Practice — Provides system design and procurement on three levels against the background of a procedure model. — user level; — conceptual explanation; — examples.