This rulemaking would request comment on whether NHTSA and EPA should reconsider certain aspects of the fuel efficiency and greenhouse gas (GHG) standards for medium- and heavy-duty on-highway vehicles and work trucks for model years beyond 2018 that were established in the agencies’ October 25, 2016 final rule. In particular, the agencies are considering whether to continue the engine standards and advanced technology incentives included in the 2016 rule, and expect to request comment on the effects of these aspects of the program and the best ways to model these effects, which were not modeled in the 2016 rule. The agencies are further considering whether the stringency of standards in later model years covered in that rulemaking as they apply to covered vehicles remain appropriate. This action would complement the separate rulemaking reevaluating the standards for trailers that the agencies are pursuing under RINs 2127-AM17 and 2060-AU50.