Heavy Duty Diesel Vehicle Inspection and Maintenance Working Group

The North Central Texas Council of Governments (NCTCOG) facilitates the Heavy Duty Diesel Emissions Inspection Working Group for jurisdictions in the United States and abroad to share information about heavy duty diesel vehicle (HDDV) emissions inspection and maintenance (I/M) programs and coordinate research and planning efforts.

Jurisdiction Program Information

Each area provides information about its program.

Jurisdiction Heavy Duty Diesel Testing Applicability Program Survey Results
Arizona Opacity
Over 8,500 GVWR Complete [PDF]
California Opacity
Emissions Control Label
Varies Complete [PDF]
Colorado Opacity
Over 14,000 lbs GVWR Complete [PDF]
Connecticut Opacity Commercial motor vehicles over 26,001 lbs GVWR or that transport 16 or more passengers  
Maine Opacity    
Massachusetts Opacity    
Nevada Opacity-random roadside    
New Jersey Opacity, annual
HD-OBD coming
Ontario, Canada Opacity Over 10,000 lbs Complete [PDF]
Utah (varies by county) Opacity    
Washington Opacity Over 6,000 lbs curb weight Complete [PDF]

The following jurisdictions have completed the program survey and indicated they do not currently perform HDDV inspections.  Please select a jurisdiction to view survey responses.


Jurisdictional representatives may access the program survey at this link to provide details of existing HDDV I/M efforts.  Please contact staff below to update information already provided.

Heavy-Duty Diesel Emissions Measurement Equipment Survey

This survey seeks to understand requirements for on-road heavy-duty diesel vehicle emissions measurement equipment. While HD diesel vehicles are the primary focus, the device could also be useful for light-duty applications.  The survey will ask to rank the importance of various features and will delve further into required specifications.  Access the survey at this link.

Upcoming Meetings

August 20, 2020 at 10:30 a.m. (US Central Time)

Existing Research


Future Research Possibilities

  • How NOx and PM are affected by reductions in opacity
  • Commercial equipment and software necessary to directly measure NOx and PM in an I/M environment
  • How well OBD identifies high emitting vehicles
  • Given the interstate travel of most of the HDD fleet, an interstate telematic OBD solution coordinated between states would be preferable to a state-by-state solution; central HDD OBD test data repository with multi-state access would also be worth researching

Conferences and Networking Opportunities


Additional Resources

Staff Contacts

Anthony Moffa
Jason Brown
Chris Klaus