A practical stepwise methodology is outlined based on the SCSC Service Assurance Guidance V2. This is explained using a real example of a highways service (based on a motorway in the UK, the M3); it also includes the services provided by vehicles and drivers when using the motorway. The contracts and agreements are indicated where available, the services identified and then the levels of service assurance flowed down, together with safety requirements. Wrappers (supplementary assurance needs) are identified and elaborated. The advantages of the service assurance approach are then discussed for this very real example and compared to more traditional systems approaches.