A Century of Environmental Technologies for Light-Duty Vehicles This paper provides a long-term view of the deployment of environmental technologies for light-duty vehicles and their implications for other vehicle attributes. It considers technologies for controlling tropospheric air pollutants and for improving fuel economy and reducing corollary greenhouse gas emissions. Since the introduction of the first controls to improve ambient air quality in the early 1960s, these technologies have gone from simple gas recirculation hose and valve systems and adjustments in carburetor air-fuel ratios to systems that continuously control vehicle operations to optimize emissions reductions and fuel economy. Not only have these technologies produced major benefits for public health and the environment, but they have also fundamentally altered the characteristics of the vehicles we drive today. And future regulations will reform the vehicle fleet even further. During the next 50 years, new vehicles will continue to be more fuel efficient, lighter, safer, emit less air pollutants and more expensive to purchase relative to current vehicles. These vehicles will be less expensive to fuel and have increased autonomy and consumer features. The impacts of future regulatory demands are simply a continuation of a long-term regulatory trend toward a safer, cleaner, and more efficient vehicle fleet. This paper relies in part on the vehicle-related reports developed for the Departments of Energy and Transportation and the Environmental Protection Agency by the National Academies of Sciences, Engineering, and Medicine. The Academies are often called upon by Federal Agencies and Congress to weigh in on critical science, technology, and policy issues, and the regulation of light-duty vehicles has been a long-term topic of interest of its sponsors. It also relies on the extensive set of materials reviewed during the course of Academies studies.