# Data sources, licenses and attribution

Checked 2026-11-07 against BusCalc's terms: commercial use; redistribution as map tiles and as facts through REST and MCP; indefinite storage; alerts; receipts; combining sources.

| Layer | Source | License | Required credit / conditions |
|---|---|---|---|
| States, counties, cities (incorporated places and CDPs) | U.S. Census Bureau, TIGERweb Generalized ACS 2025 (1:500k) | Not copyrighted (U.S. Government) | Credit the U.S. Census Bureau. "TIGER" is a Census trademark. Boundaries are statistical. |
| Major roads | BTS NTAD North American Roads (U.S. features only) | U.S. Government work, unrestricted | Credit FHWA/BTS NTAD. Canadian and Mexican features are excluded. |
| Mile markers | FHWA HPMS Spatial All Sections 2024 (calculated) | Public domain, U.S. Government | Credit FHWA |
| Iowa reference posts and rest areas | Iowa DOT | CC BY 4.0, plus Iowa DOT GIS Data Terms of Use | "Iowa DOT". Data is as-is; Iowa DOT's terms include an indemnity clause. |
| Bridges | FHWA National Bridge Inventory via BTS NTAD (as of 2025-06-20) | U.S. Government work, unrestricted | Credit FHWA and BTS |
| Truck parking | FHWA Jason's Law survey via BTS NTAD (2019) | U.S. Government work | Credit FHWA/BTS |
| Intermodal rail terminals | BTS NTAD Intermodal Freight Facilities | U.S. Government work | Credit BTS |
| Alternative fuel and EV stations | Alternative Fueling Stations via BTS NTAD (originally from DOE AFDC) | U.S. Government work | Credit BTS / NREL AFDC. Do not use DOE, NREL or Alliance names in advertising. |
| Historic places and National Historic Landmarks | NPS National Register of Historic Places, public locations | Public (NPS) | Credit NPS. Restricted or sensitive sites are excluded by NPS. Never add them from other sources. |
| National park boundaries | NPS Land Resources Division | U.S. public domain | Credit NPS (appreciated) |
| Park entrances and visitor centers | NPS Public POIs | Public (NPS) | "Do not use for navigation, emergency response …" Shown as reference only. |
| Federal lands | USGS PAD-US 4.1 (federal fee managers) | Public domain | USGS Gap Analysis Project, 2025, PAD-US 4.1, doi:10.5066/P96WBCHS. Not legal boundaries; no area figures finer than 1,000 ha. |
| Communities, rivers, reservoirs, passes | USGS GNIS | Public domain | "Courtesy of the U.S. Geological Survey" |
| Rest areas (California) | Caltrans | CC BY 4.0 | Credit "Caltrans" |
| Numbered exits (Massachusetts) | MassGIS | Public resource: "may be used by anyone for their purposes" | Credit "MassGIS (Bureau of Geographic Information), Commonwealth of Massachusetts EOTSS" |
| Land, lakes, rivers (base) | Natural Earth | Public domain | Optional: "Made with Natural Earth" |
| Route junctions; state and county line crossings | Derived by BusCalc from NTAD roads and Census boundaries | Inherits public-domain sources | Credit the sources above |
| Map software | MapLibre GL JS (BSD-3), PMTiles (BSD-3), tippecanoe (BSD-2, build only) | Open source | Keep the license notices in `lib/` |
| Fonts | Noto Sans glyphs via Protomaps basemaps-assets | SIL Open Font License | Keep `fonts/OFL.txt` |

**Rules for using this data:**
- No agency logos. The NPS arrowhead may not be used without written permission.
- Show "Not affiliated with or endorsed by any U.S. government agency." The map's attribution line already says this.

**Left out because their terms didn't fit BusCalc's** (a written permission request would be needed):
- **Exits:** Pennsylvania (no redistribution). New York, Washington, Georgia, Connecticut and New Mexico state no grant. Maryland, Florida and New Hampshire are conditional. Utah's live service is UDOT's, which carries a disclaimer only.
- **Rest areas and welcome centers:** Michigan (indemnity clause). Texas, Washington, Indiana, Kansas, Vermont, Pennsylvania, West Virginia, Ohio, Utah, Colorado and Georgia state no grant. Maryland, Minnesota and New York are conditional. Florida and Illinois are conditional under their state public-records and open-data laws.
- **Posted mile markers:** other states' sign layers are silent or restrictive. Maryland's posted markers can be added once its server is back.
- **DOE AFDC direct API:** requires a key and registration. The NTAD copy is used instead.

PMTiles 4.3.0 reference implementation: [BSD 3-Clause license](lib/PMTILES-LICENSE).