Fleet MPG vs. CAFE Trajectory (2026 – 2031)
| Model Year | Target (Prior) | Target (Revised) | Planned Fleet MPG | EV Share | Status (Revised) | Penalty / Surplus ($M) |
|---|
How CAFE Standards & Regulatory Shifts Impact Automakers
The Corporate Average Fuel Economy (CAFE) program, regulated by the National Highway Traffic Safety Administration (NHTSA) under 49 U.S.C. Chapter 329, mandates production-weighted average fuel economy for passenger cars and light trucks. Lowering standards decelerates mandatory EV adoption curves and reduces multi-billion dollar civil penalties for traditional combustion fleets.
1. Mathematical Harmonic Mean
CAFE calculations rely on harmonic averaging: Fleet MPG = Total Units / Σ (Units_i / MPG_i). A small fraction of zero-emission vehicles (rated above 100+ MPGe under test cycles) disproportionately lifts total fleet score.
2. Footprint-Based Attribute Curves
Vehicles with larger wheelbases and track widths (light trucks, full-size SUVs) are held to lower fuel economy stringencies. High truck mixes soften aggregate compliance hurdles under revised curves.
3. Statutory Penalty Economics
Automakers failing to meet targets must purchase compliance credits from electric competitors or pay NHTSA civil penalties ($16 per tenth of an MPG shortfall multiplied by the entire manufactured fleet).
View Regulatory Constants, Statutory Notes & Citations
Baseline Assumptions: BEV test cycle equivalent credit values modeled at harmonized 108 MPGe. Light truck stringency offset modeled according to NHTSA 2024 final rule footprint distribution (49 CFR Parts 531 & 533). Prior Biden targets assumed ~8% annual stringency increase for passenger cars and ~4% for light trucks through MY 2031. Revised rules decelerate annual stringency growth to approximately 1.5% to 2.0% annually.