1、www.theicct.org communicationstheicct.orgtheicct.org WORKING PAPERFEBRUARY 2025Hybrid vehicle technology developments and opportunities in the 20252035 time frame Aaron Isenstadt and Peter SlowikSUMMARYIn the United States,greenhouse gas(GHG)emission standards have assisted in the proliferation of e

2、lectric vehicles without requiring GHG emission reductions for each specific powertrain.Indeed,fleet-average emission standards can be met with greatly increased sales of zero-emission vehicles and little or no improvement in the combustion engine-based fleet.In its final rulemaking for model years

3、20272032,the U.S.Environmental Protection Agency projected that its rule could result in a 68%electric vehicle sales share(consisting of 56%battery electric and 13%plug-in hybrid electric)by 2032 and at the same time,the average emissions of the remaining non-electric-vehicle fleet would increase(U.

4、S.Environmental Protection Agency,2024b).This phenomenon is referred to as“backsliding.”At the state level,the California Air Resources Board has observed with its fleet averaging standards that increasing sales of zero-emission vehicles creates a risk of combustion engine vehicle backsliding.The in

5、crease in emissions may result from a variety of factors,including manufacturers discontinuing models with low carbon dioxide(CO2)emissions,converting low-emitting combustion models to zero-emission vehicles,removing CO2-reducing technologies on individual models,or neglecting to implement CO2-reduc

6、ing technologies while calibrating vehicles for improved performance only.Given the backsliding risk,the California Air Resources Board has proposed to promulgate standards that will ensure emissions from vehicles sold in the state with internal combustion engines(ICEs)including plug-in hybridsconti