National geometric design policy — the conceptual backbone (sight distance derivations, curves, intersections) that FDM/Greenbook implement for Florida.
Why: when Florida manuals are silent or you need the why behind a criterion; expert-level justification in variances.
When:
- ISD/SSD derivations
- design speed philosophy
- unusual geometry
Example questions:
- ISD for left turn from stop across 3 lanes at 45 mph?
- SSD on grade?
Related: FDOT Design Manual (FDM) · Highway Safety Manual (HSM)