# Data Dictionary - US Road Traffic Volume - monthly vehicle-miles travelled (VMT), cleaned Parquet

**Units:** all `vmt` values are in **million vehicle-miles**.  Times are UTC.

| column | type | description |
|---|---|---|
| `zone` | str | US (national) |
| `ts` | timestamp (UTC) | Month |
| `vmt` | float | Monthly vehicle-miles travelled (millions) |
| `unit` | str | Unit |
| `res_min` | int | Native resolution (monthly) |

*Source: U.S. Federal Highway Administration (FHWA) - Traffic Volume Trends.*