HeadwayWhere the numbers come from.
"Your agency is already analyzed" is a claim worth auditing. This page shows the 17 data domains behind the Transit Planning OS — every source, its refresh cadence, its validation, and how the key calculations work — so your IT, compliance, and procurement reviewers can check the foundations before anyone signs anything.
Data sources
Every analysis draws from these sources. Cadence describes how often each is refreshed.
| Source | What it provides | Cadence |
|---|---|---|
| GTFS Schedule (MobilityData catalog, open GitHub mirror) | ~1,150 US schedule feeds: routes, stops, trips, stop times, calendars, shapes. Normalized into PostGIS on demand. | Catalog synced nightly; per-agency feed parsed on demand. |
| GTFS-Realtime | Hundreds of US RT feeds: vehicle positions and trip updates for live operations and validation. ~40% require agency credentials. | Polled per-feed (≈15–60s) when active. |
| National Transit Database (NTD, FTA via Socrata) | 2,200+ reporting agencies: ridership (UPT), passenger miles, vehicle revenue miles/hours, fleet size (VOMS), operating expenses, peer context. | Annual NTD release. |
| Census ACS (vintage 2022) | 239k+ block groups across 50 states: race/ethnicity, income for Title VI equity overlays. | ACS annual vintage. |
| LEHD LODES (workplace area characteristics) | Jobs by block for access-to-opportunity analysis. | Annual (loaded per state). |
| APTA | Public Transportation Fact Book agency stats plus the national quarterly ridership-by-mode trend. | Annual Fact Book + quarterly ridership. |
| Canonical GTFS Validator (v8) | Schedule feed quality notices, rolled up per feed version. | Run on each feed ingest. |
The HeadwayForge data catalog
The full set of data sources behind the Transit Planning Operating System — across every planning domain, with live load status, access method, and the datasets each source provides.
How key calculations work
Each output is built from a documented method. No black boxes — here's what's actually computed.
GTFS & GTFS-Realtime validation
Feeds run through the Canonical GTFS Validator; notice counts are summarized per feed version, and RT feeds are checked for staleness, missing vehicles, and decode errors so analysis starts from trustworthy data.
R5 access analysis assumptions
Travel-time isochrones and cumulative-opportunity counts (jobs/people reachable in 15/30/45 min) are computed with an embedded R5 (Conveyal) routing engine over the GTFS network plus walking; departure window and walk access are configurable.
Census & ACS handling
ACS block-group attributes (race/ethnicity, income) join to TIGER block-group geometry; equity overlays count population within walk buffers of frequent service, broken out by minority and low-income status per FTA Circular 4702.1B.
NTD peer selection
Peer sets are built from agencies sharing the same urbanized area and primary mode, following standard FTA/NTD peer-grouping convention, with a curated GTFS↔NTD crosswalk to match feeds to reporters.
Service supply metrics
Trips/day, headways by period, and span of service are derived directly from the agency's parsed GTFS for the representative service day; route directness and stop spacing come from shapes and stop geometry.
Confidence & traceability
Every figure traces back to a named source and the feed version or data vintage it came from, so outputs can be audited and explained.
Sources
The specifications, datasets, and federal guidance the methodology relies on:
Start from data you can defend.
Open any US agency free and see exactly which feeds, vintages, and validation results back the analysis — then see what each plan adds when the team is ready.