As policymakers and stakeholders in India begin the regulatory development process for fuel efficiency standards for new heavy-duty vehicles (HDVs), one of the key areas of debate has been whether or not separate performance standards for engines are an appropriate first step. Based on the most recent analysis, the ICCT supports engine-based standards in the first phase HDV fuel efficiency regulation in India, for three reasons: to realize fuel savings as soon as possible; to leverage existing testing facilities and expertise; and to limit complexity. Furthermore, the analysis indicates that regulatory experience and technology cost-effectiveness data from the United States provide evidence that engine technologies are quite cost-effective compared technology interventions in other vehicle areas.