The Advanced Clean Cars II (ACCII) standard ensures gradual reductions in climate-disrupting and health-harming tailpipe pollution by steadily phasing in supply targets for manufacturers to deliver higher numbers of zero-emission light-duty vehicles to participating states. ACCII does not ban internal combustion engines, as plug-in hybrid electric vehicles are allowed indefinitely under the program. ACCII does not impose requirements on vehicles that are already on the road or on the secondary market.