How CAFE & EPA Standards Drive the Fleet
Corporate Average Fuel Economy (CAFE) and EPA greenhouse gas tailpipe rules mandate fleet-wide sales-weighted efficiency thresholds for automakers. When rules are relaxed or scaled back:
- Fleet inertia matters: With over 285 million registered vehicles in the U.S. and an average operational lifetime of 12.5 years, changing new vehicle sales takes 10–15 years to fully propagate through on-road gasoline demand.
- The Light Truck loophole: Light trucks and SUVs carry lower nominal fuel economy requirements than passenger sedans; as their sales share expands above 70%, overall fleet gasoline savings compress.
- Consumer fuel sensitivity: Every 1 mpg drop in fleet average over a 16-year window equates to roughly 8–12 billion additional gallons of gasoline burned annually by American households.
Simulation Methodology & Assumptions
This policy laboratory implements an empirical cohort turnover engine calibrated to EPA Automotive Trends and BTS National Transportation Statistics:
- Annual Sales & Scrappage: Steady baseline of 15.5 million new registrations per year with an S-curve Weibull survival decay distribution (scrappage rising steeply after year 8).
- Real-world vs Test-cycle gap: A 18% adjustment factor is applied to account for on-road air conditioning, aggressive acceleration, and cold weather.
- Emissions conversion: Fixed EPA standard of 8,887 grams of CO2 per gallon of non-ethanol gasoline burned.