Skip to main content
Skip global navigation and go to main content

California approves heavy duty vehicle smog check program

First in nation large truck and bus smog check program

Posted December 17, 2021

The California Air Resources Board (CARB) recently approved a ‘smog check’ regulation for medium- and heavy-duty trucks and buses, those with a gross vehicle weight rating (GVWR) greater than 14,000 pounds. CARB estimates approximately one million vehicles, operating in the state, will be affected by the new regulation. Once fully in place, the regulation is expected to reduce NOx and fine particle diesel pollution by as much as 82 tons per day.

Initially the program includes emission control system inspections twice-a-year, with a phased-in increase to four inspections per year for trucks with on-board diagnostics. Like the existing passenger cars and light-duty truck smog check program, vehicle registration in the state will require passing the inspections. However, different from the smaller vehicle program, there is no requirement to go to a smog check station. Using onboard diagnostics (OBD) owners will be able to complete the required test and send the data without going to a testing location. Older heavy-duty vehicles, without OBD will continue the current opacity testing requirements with an added visual testing component, twice each year.

Compliance timeline:

January – June 2023: Phase 1 – Initial compliance certification

  • Outstanding “high emitter” citations must be resolved
  • Vehicles registered into program database
  • Annual program fees begin

June – December 2023: Phase 2 – Enforcement begins

  • Vehicle registration denied for CA-registered vehicles without certificate
  • Enforcement when operating in California without certificate

January 2024 and beyond: Phase 3 – Periodic testing

  • Owners must meet periodic testing requirements
  • Outstanding “high emitter” citations must be resolved
  • Continued payment of program annual fee


This article was written by Laura Verity of J. J. Keller & Associates, Inc.

Looking for more on workplace safety?

Get the information and products you need to stay on top of industry changes and comply with regs.

Learn More

J. J. Keller's free Workplace SafetyClicks™ e-newsletter brings quick-read safety and compliance news right to your inbox.

Sign up to receive Workplace SafetyClicks™