The technology assessments conducted by the Environmental Protection Agency and the National Highway Traffic Safety Administration to inform the 2017–2025 passenger vehicle fuel economy and greenhouse gas emissions regulations were done five years ago. Since then, innovations in vehicle technologies have come rapidly, enabled by computer-aided design tools and computer simulations.
This paper provides an analysis of lightweighting (mass reduction) developments and trends in passenger vehicle design and technology. There are two different ways to reduce costs of materials used in building cars and trucks. One is to optimize design and thickness. The second is to use higher-strength and lighter materials.
Advances in lightweighting designs and technology have surpassed the projections used to inform the rulemaking. Stronger and lighter materials are available at lower costs than assumed. Better modeling/simulation tools and joining techniques have opened the floodgates to unprecedented levels of material/design optimization.
Suppliers are rapidly developing new materials and methods, as well as computational tools for simulating full vehicles all the way down to nanoscopic material behavior. These tools and techniques build on a sophisticated toolkit that manufacturers are using to make vehicles stronger and lighter. Many recent redesigns have reduced vehicle weight by at least 4%, already meeting or exceeding projections for 2021. Numerous material improvements are in development that were not evaluated for the rulemaking, such as higher-strength aluminum, improved joining techniques for mixed materials, third-generation steels with higher strength and enhanced ductility, a new generation of ultrahigh-speed-steel cast components, and metal/plastic hybrid components.
It appears likely that the cost of reducing weight will be less than one-third of the projections used for the rulemaking. When the other benefits of reducing weight are considered (ride, handling, braking, performance, load capacity), it is clear that implementation of lightweight materials and better design will be limited only by the speed at which computational tools improve and better materials can be brought to the market. The current generation of vehicle redesigns is routinely achieving about 5% weight reduction on average (some are much higher). There are two redesign cycles before 2025, and given the accelerating pace of innovation it is reasonable to anticipate that each of these redesign cycles should achieve at least a 5% weight reduction. In summary, a 15% weight reduction, approximately, should be feasible by 2025 at costs about one-third of those estimated in the 2017–2025 rule.