This paper will examine the need to adopt a whole vehicle top-down structured approach to the design of future vehicle electronic control systems.The benefits of an architected design include: improved performance, greater flexibility, improved diagnostic capability, reduced number of ECUs, reduced wiring and improved fault tolerance. These will be assessed together with the constraints such as: safety, data bus technology, response time requirements and commercial confidentiality. It will be argued that the benefits can only be achieved by a rigorous analysis and prioritisation of the system requirements, followed by coherent system design. The partitioning of the system functions into logical and then physical groups is seen as the key activity in the design process. Various methods for partitioning the system such as functional, geographical, event-driven and object-oriented will be suggested and different schemes will be proposed for different areas of functionality.Practical implementations of an architected design will be described and assessed.