How do you develop a systematic aerodynamic drag reduction roadmap for a vehicle program?

Drag reduction roadmap involves: Baseline assessment decomposing total drag into components (body shape, cooling, underbody, wheels, protrusions), identifying reduction opportunities with technical and cost feasibility, prioritizing by benefit-to-cost ratio, accounting for design constraints (styling, package, regulations), tracking through development with CFD and wind tunnel checkpoints, and validating production intent. Key areas typically include: A-pillar/mirror optimization, underbody panels/diffuser, active grille shutters, wheel/tire aerodynamics, and rear-end shape. Roadmap includes fallback options for styling constraints. Target is typically 0.02-0.04 Cd reduction over previous generation, translating to measurable range/efficiency improvement.