Developed a new methodology to define the owner operator Key Performance Indicators (KPIs) in a new motorway build. This methodology adapts the fundamental diagram to develop a KPI framework for motorway performance. In a worlds first, the methodology was used in collaboration with Leighton Contractor’s to monitor travel times and motorway performance. This framework was then used to develop the contracted performance KPIs that delicately balance the business tension between the infrastructure owner and the operator. These performance KPIs are designed to financially incentivise the operator to maintain a high level of travel time reliability. The KPI definitions that were initially proposed were based on criteria that would have led to penalties being applied, even under normal operation. Hence a more robust and equitable approach to KPI calculation was required. This case study reports on the design and development of the approach, which was accepted by all stakeholders in the project. The fundamental diagram is used to define a base line for equilibrium traffic conditions. Calculation of the fundamental diagram is based on a recently proposed model by Wang, Li, Chen & Ni (2010). We then constructed an envelope around the fundamental diagram. where the boundaries of the envelope signify normal or “healthy” traffic conditions. Since being adopted, travel time KPI penalties are now only triggered for traffic flow data points that are outside the agreed “healthy“ flow envelope.