CARB Tier 5 Off-road : A summary of elements being considered

California Air Resources Board (CARB) is working on the next set of “Tier 5” regulations for the off-road sector, covering diesel engines used for construction and farming. Here’s a summary of the current thinking as discussed in the latest workshops. 

What are the changes being considered? 

Relative to Tier 4 Final standards:

  • Up to 75% reduction in NOx & PM for diesel engines < 56 kW
  • 75% or 90% reduction in NOx & PM for diesel engine 56 – 560 kW
  • 50% reduction in NOx & PM for diesel engines > 560 kW

 

Equipment < 19 kW to be zero emission (Small off-road emission – SORE – regulations)

 

First-ever CO2 tailpipe standard for diesel engines : 5 – 8.6% reduction

 

New Low Load Application Cycle (LLAC) for certification

 

Increased useful life from 8000 hrs to 12,000 hrs for 56 – 560 kW engines. Extended warranties tbd.

 

Idling measures (engine shut-off for prolonged idling)

 

Manufacturer-run in-use testing program – could be moving average window (MAW) type similar to on-road

Collaboration with EPA is a must

Note that in the non-road sector, California can not set standards for new farm and construction equipment under 175 hp. Further, currently there is no restriction on sale of equipment from other states. Thus CARB will look to EPA to set tighter nationwide standards for maximum impact.

Timing

Timing is unclear at this point, but given that EPA low NOx regulations for on-highway trucks starts in 2027, the non-road regulations should start at least a year or two later. Also, note that the low load application cycle (LLAC) is yet to be fully developed so there is more work ahead.

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