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US EPA Cleaner Trucks Initiative—progress update

22 November 2019

The US Environmental Protection Agency (EPA) expects to release a Notice of Proposed Rulemaking in 2020 for their Cleaner Trucks Initiative (CTI), according to a presentation at the Integer Emissions Summit USA by Brian Nelson, Director, Heavy-Duty Onroad and Nonroad Center at the EPA. The CTI is intended to update NOx standards for on road heavy-duty trucks and engines. Final Rulemaking should then occur one year later. The updated rules would most likely apply to MY 2027 engines and vehicles.

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Currently the EPA is engaging with the California Air Resources Board (CARB) staff to ensure consistency with the CARB’s Heavy-Duty Low NOx program. CARB’s formal proposal is also expected in 2020 but some NOx reductions are likely to be required already for MY 2024. This could cause divergence between CARB and EPA requirements for MY 2024-2026. As long as the two agencies continue to cooperate, the programs are expected to align starting MY 2027 when CARB’s final requirements apply.

Details of CARB’s plan were contained in a feasibility assessment released in April 2019. These details have been further refined with updates provided at a CARB workshop in September 2019. According to the workshop materials, a heavy-duty engine NOx emission standard between 0.015 and 0.030 g/bhp-hr and a heavy heavy-duty diesel engine useful life period of up to 850,000 miles/18 years would become effective from 2027.

For in-use testing, a moving-average window (MAW) approach similar to that used for Euro VI ISC is being considered. However, instead of the defined drive cycle as used for ISC, grouping MAWs into separate bins is being considered. Bins could be defined by the average window power, or some other criteria. All MAWs would be attributed to a bin respective to their average power (or other criteria). Each bin would then be evaluated against the appropriate test cycle standard (e.g., idle, LLC and FTP/RMC).

For the warranty requirements, the manufacturer pays if part replacement is scheduled during useful life for the catalyst beds, DPF elements, turbochargers (MY 2022+) and EGR systems (MY 2022+).

The September workshop materials also provided updated details for the options to demonstrate full useful life (UL) emissions compliance. For LHDD and MHDD, aging the aftertreatment system to full UL on an engine dynamometer is presented as the only option. For HDDD, two options are presented:

  1. Full UL aging of the aftertreatment system with defined cycles on an engine dynamometer (9800 h);
  2. 4600 h aging of the aftertreatment system on an engine dynamometer using defined cycles, then 1/2 UL (~600 h) aging using the Diesel Aftertreatment Accelerated Aging Cycle (DAAAC) protocol [4574], followed by an additional 300 h aging on an engine dynamometer. This option would require in-use NOx sensor data submittal—most likely via telematics.

The EPA acknowledged the need for further NOx reductions in December 2016 in response to a petition from about 20 air quality agencies asking the EPA to undertake a new heavy-duty NOx rule. The CTI was announced in November 2018.

The Integer Emissions Summit was held November 19-20 in Indianapolis.

Source: US EPA | CARB