Transport Refrigeration Residual Risk Reduction Airborne Toxic Control Measure (TR4 ATCM)

This page last reviewed January 18,, 2018

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Posted July 21, 2017

Public Workshop Series

Workshop Series #2:
     Date:   Wednesday, August 16, 2017
     Time:   9:30 a.m. - 11:30 a.m.

     Place:  California Environmental Protection Agency Headquarters
                Sierra Hearing Room
                1001 I Street, 2nd Floor
                Sacramento, California  95814

The Sacramento workshop will also be webcast on the day of the workshop only.
      The webcast connection is at:

     Date:    Friday, August 18, 2017
     Time:   1:00 p.m. - 3:00 p.m.

     Place:  Riverside County Administration Center
                 4080 Lemon Street, 1st Floor
                 Riverside, California  92501

     Public Notice (Spanish version)
     Presentation (with Emission Inventory slides) (Spanish version - does not include Emission Inventory slides)

cold-storage-tru Background:

California needs to reduce residual public health risk from Transport Refrigeration Units (TRU) near distribution centers and other facilities where TRUs and TRU generator sets congregate; as well as achieve emission reductions while in transit, especially along freight corridors and near the most impacted communities. California has recently set new targets for reducing air pollution, including decreasing greenhouse gas (GHG) emissions to 1990 levels by 2020, to 40 percent below 1990 levels by 2030, to 80 percentbelow 1990 levels by 2050, and cutting petroleum use by cars and trucks by up to half from current 2015 levels by 2030.   Improving freight efficiency and transitioning to zero or near-zero emission technologies will help achieve these goals by reducing toxic air contaminant emissions, criteria pollutant emissions (e.g. nitrogen oxides, non-methane hydrocarbons, and particulate matter), and GHG emissions.

TRUs are currently defined as refrigeration systems that are powered by internal combustion engines (inside the unit housing). They control the environment of temperature-sensitive products that are transported in refrigerated trucks, trailers, railcars and shipping containers.  They may be capable of cooling or heating.  TRUs are used to transport and store many products, including, but not limited to food, pharmaceuticals, plants, medicines, blood, chemicals, photographic film, art work, and explosives.  Transport refrigerators (TR) are similar in most regards to TRUs; but they do not have an internal combustion engine inside the unit housing.  

Some companies use TRUs for extended cold storage during the four- to six-week period before major holidays and events.  Distribution centers and grocery stores are known to run out of cold storage space in their buildings, so they store overflow goods in TRU-equipped trucks and trailers outside the grocery stores and distribution centers. Some distribution centers also operate in a way that causes TRU-equipped trucks and trailers to be parked or queued for extended times, waiting for an open loading dock space or manpower to unload goods, or waiting for dispatch or driver pick-up.  These operations sometimes continue for several days.  A few distribution centers are using refrigerated trailers equipped with all-electric stationary TRs (e.g. Carrier Transicold's Vector 8100) that are plugged into the electric power grid while in use.

In April 2015, ARB staff released a Sustainable Freight Discussion Document which discussed a potential control measure to limit stationary operation of internal combustion engine-driven TRUs for cold storage and incentives to install infrastructure at affected locations.  Current control measure concepts also include transitioning California's TRU fleet to zero-emission technology.

Near-Term Control Measure Concepts:

Stationary operating time limits would be phased in over time at grocery stores, distribution centers, cold storage warehouses, truck stops, packing houses, cross-dock facilities, trnsloading facilities, third-party logistics facilities, and facilities serviced by railroad spurs.  Later phases may further reduce the stationary operating time limit and affect more types of facilities or locations.  The control measure would encourage more energy-efficient operations that reduce stationary internal combustion TRU engine operating time, resulting in reduced emissions of toxic air contaminants, criteria pollutants, and GHGs. Compliance could be achieved several ways:

  1. Use effective logistics, GPS tracking systems, and dispatch procedures to improve load scheduling;
  2. Use electrically-driven TRs or TRUs that plug into lectric grid power while stationary (e.g. all-electric TRs, hybrid-electric TRUs, or TRUs equipped with electric standby); 
  3. Use cryogenic TRs (e.g. using liquid nitrogen, liquid carbon dioxide, or liquid air to cool the cargo space);
  4. Build additional facility cold storage capacity.

Long-Term Control Measure Concepts:

The transition to zero-emission technologies will be phased in over time, possibly beginning in the 2020 decade and extending out to 2050.  

This  control measure is only in the preliminary concepts phase, and workshops to discuss the concepts with stakeholders began April 13, 2016.  In addition to producing near-term GHG and criteria pollutant emission reductions, the control measure could help to advance zero and near-zero emission transport refrigeration system commercialization by increasing the earlier penetration of infrastructure that will be needed for those technologies (e.g. electric power plug infrastructure).  The same infrastructure that is used to comply with the stationary operating time limits in the TR4 ATCM could be used as zero and near-zero emission technologies become commercially ready. 

Previous Posts:

Posted April 25, 2017

ARB has published a Request for Proposal (RFP) No. 16TTD008 titled "Data Collection and Business Case Study for eTRUs."  This RFP can be found at the California State Contracts Register at:  Any questions/comments should be emailed to or by phone to (916) 322-8452.

Posted March 1, 2017

Proposition 1B Funding

ARB Executive Order G-17-004 made changes to the Proposition 1B Final 2015 Guidelines for Implementation (Program Guidelines), which may benefit refrigerated fleets and grocery store chains that use TRUs for cold storage behind grocery stores.  Click here for further description of these changes.

Posted September 7, 2016

Clean TRU Technology Webinar

ARB hosted a "Clean TRU Technology Webinar" on August 31, 2016, where staff and clean technology manufacturers discussed clean TRU technology options and the availability of Proposition 1B funding.  See links to the agenda and slides handout, below.  A video recording of the webinar is available here.
     Slides Handout

Posted March 8, 2016

Public workshop Series 

California Air Resources Board (CARB) staff conducted a series of public workshops to discuss concepts to reduce air pollution emissions from TRUs.

Workshop #1:  
     Date:   April 13, 2016
     Time:  10:00 a.m. to 12:00 p.m.
     Place:  Sierra Hearing Room (2nd floor)
                1001 I Street, Sacramento, California 95814

Public notice
                This workshop will also be webcast.  The webcast connection is at:

Posted October 12, 2015

Proposition 1B funds are currently available for the replacement of existing diesel TRUs with zero-emission TRs, as well as the purchase and installation of electric and/or cryogenic infrastructure.  Such infrastructure could be used for zero-emission units, or hybrid electric TRUs and TRU equipped with electric standby. Solicitations open periodicaly at certain California air districts, which are listed at ARB's Goods Movement Website.

Posted August 27, 2015

Zero Emission Transport Refrigerator Technologies List.  
This list includes a brief technology description, manufacturer's company name, brand or model, website address, and contact information.  A zero emission transport refrigerator must not be powered by an internal combustion engine in any way (i.e. zero tailpipe emissions).  Electric power for refrigeration system compressor, fans, and controls may come from on-board batteries, provided they are not re-charged by an alternator or generator that is driven by the vehicle engine or powertrain, trailer wheels, trailer axle/differential, or any other contrivance that adds to the vehicle drag and/or engine load.  Examples of zero emission TRs include, but are not limited to, TRs with refrigeration system and/or fans that are powered by batteries when on-road, and use battery chargers that are plugged into the electric power grid while stationary or connected to on-board solar panels.

Posted July 31, 2015

The California Air Resources Board (ARB/Board) announces the release of the draft document “Technology Assessment: Transport Refrigerators." The draft technology assessment can be viewed and downloaded from the ARB’s technology and fuels assessment webpage at:
If you have questions regarding the draft technology assessment, please contact Mr. Rodney Hill, Staff Air Pollution Specialist, at 916-327-5636, or email to 

Sign up for the TRU email list to get news and notices related to the TR4 ATCM and incentive funding for zero-emission TRs and related infrastrucutre.