Zero Emission Ancillaries – Developing the Evidence Base - Phase 1

Background and Challenge

This project focuses on ancillary engines used for purposes other than vehicle propulsion, which includes auxiliary transport refrigeration units (auxTRUs). AuxTRUs are climate-controlled units powered by their own auxiliary engine, independent of the vehicles propulsion engine. Subsequently, these engines are classified as Non-Road Mobile Machinery (NRMM).  

AuxTRUs are commonly attached to heavy goods vehicle (HGVs) across cold chain logistics (temperature controlled supply chains as seen in the food and pharmaceutical markets) thus contribute to the on-road air quality mix despite falling under the NRMM regulations. The total emissions auxTRUs contribute to the transport sector remain largely unknown.  

Phase 1 of this project encompasses the work Zemo Partnership has completed with Innovate UK (2019) and Transport Scotland (2021). It covers the development of emissions test procedures for auxTRUs and the building of the energy consumption and emissions performance evidence base. 


  • To build the evidence base relating to commercial vehicle ancillary systems, including but not limited to 'transport refrigeration units' (TRU).
  • To raise awareness of the GHG emission impact of ancillary systems.
  • To promote the TRU test report on Zemo Partnership’s website and seek external presentation opportunities.

Actions and Outputs

  • Publication of the “Development of Emissions Testing Procedures for Transport Refrigeration Units (TRUs)” report (Innovate UK) 
  • Publication of the “Emissions Testing of Two Auxiliary Transport Refrigeration Units” report (Transport Scotland) 
  • Dissemination workshop for the TRU test report 


  • Publication of the “Development of Emissions Testing Procedures for Transport Refrigeration Units (TRUs)” report – June 2019 
  • Publication of the Emissions Testing of Two Auxiliary Transport Refrigeration Units report – July 2021 
  • Ongoing promotion and engagement – through to March 2022 
Brian Robinson

Brian Robinson

Commercial Vehicle Emissions Consultant

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