# Oregon — Vehicle emissions testing: which counties require it, in which states

For Oregon, counties where testing is required is the Portland and Medford areas; how often is biennial; program / authority is Vehicle Inspection Program, verified against its source on 2026-08-19.

- **State:** Oregon _(our reading, not quoted from the source)_
- **Counties where testing is required:** the Portland and Medford areas _(verified: appears in the quote below)_
- **How often:** biennial _(verified: appears in the quote below)_
- **Program / authority:** Vehicle Inspection Program _(verified: appears in the quote below)_

## What the source says

> To address the leading cause of pollution, Oregon operates a biennial vehicle emissions testing program in the Portland and Medford areas. Vehicles registered within the two testing boundaries must pass an emissions test in order to be re-registered with the Oregon Department of Transportation, Driver and Motor Vehicle Services.

## Source

- https://www.oregon.gov/deq/Vehicle-Inspection/Pages/About-the-program.aspx

Last verified: 2026-08-19. Review by: 2027-08-19.
Part of [Vehicle emissions testing: which counties require it, in which states](https://referencesource.org/vehicle-emissions-testing-by-state/).