National research: NCHRP reports (free PDFs), TRB committees, TRID literature database, Annual Meeting papers.
Why: when a question has no manual answer (“what taper works for X?”), NCHRP likely studied it; also your future paper venue.
Go-to reports to locate:
- access management (NCHRP 420 lineage)
- left-turn accommodations
- roundabouts (NCHRP 672)
- traffic calming syntheses
- parking-related syntheses
Verify current report numbers before citing.
When:
- methodology defense
- literature checks
- deep dives
See also: FHWA Resources · Workflow - Research and Source Vetting · CUTR