California Air Resources Board

The manufacturer-run Heavy-Duty In-Use Testing Program (HDIUT) is a mandatory program for heavy-duty engine manufacturers (OEMs). Engines above 8,500 lbs. gross vehicle weight rating (GVWR) are tested following diesel engine standard and test procedures, specified in 40 CFR 86 and 13 CCR 1956.8 to verify the in-use emissions compliance. Every year CARB in coordination with the U. S. Environmental Protection Agency (U.S. EPA) select OEMs and their engine families for emission testing.

Upon receiving the test order for a specific engine family, the OEM must conduct real-world on-road testing of in-use engines under conditions reasonably expected to be encountered during normal vehicle operation. During the in-use testing, the OEM should measure real-world emissions from exhaust and collect other data such as engine parameters. The OEM must complete all the required testing and reporting, as specified in 40 CFR 86 and California Test Procedures, to both of U.S. EPA and CARB within 18 months from the receipt of the test order.

Upon the receipt of all the data and required information from the OEM, CARB starts the examination process and verify that the emissions meet the in-use emissions standards and test requirements. When CARB finds non-compliance of the in-use testing and/or emissions, CARB engages with the OEM to discuss additional testing (if needed), and/or remedial actions, including emissions recalls. The OEM submits HDIUT data through HDIUT Manufacturer Submit (HMS) system to CARB following HDIUT Data Submittal Workshop Slides. More information is available on the CARB webpage, How to Use HMS. 

Those data submitted to both EPA and CARB are available on an EPA’s public web page (Manufacturer-Run In-Use Testing Program Data for Heavy-Duty Diesel Engines | US EPA) after redacting Confidential Business information (CBI).