TRB’s methodologies for capacity/LOS — signalized & unsignalized intersections, segments, freeways, multimodal.
Why: every LOS number in a TIA traces to an HCM method; Synchro/HCS implement it and their settings ARE HCM inputs.
When:
- LOS analysis
- interpreting delay thresholds (signalized A≤10s … F>80s; unsignalized F>50s)
- choosing method when software results diverge
Verify the delay threshold table against the current edition before citing.
Example questions:
- why do Synchro “Percentile” and HCM delays differ?
- when is HCM unsignalized method invalid (e.g., near signals)?
Spawn: LOS threshold cheat note · Synchro QAQC Checklist cross-links.