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.

Upcoming Meeting:

Thursday, AUGUST 15, 2024 10:30am-12:00pm (CST)

Past Meetings


Map of I/M Programs by State*


Map current as of 2023. Data pulled from each state's I/M program website.

Heavy-Duty Diesel Vehicle Emissions Inspection Survey

The following jurisdictions indicated they do currently perform HDDV inspections.


The following jurisdictions indicated they do not currently perform HDDV inspections.


Jurisdiction 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 Vehicle 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.

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