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UPDATED CURED TO V3A

23-01-2018

Air Quality Consultants has updated its Calculator Using Realistic Emissions for Diesels (CURED) sensitivity test for vehicle emissions to Version 3A (CURED V3A), available here.

The CURED model was originally created in recognition of the disconnection between ‘official’ emissions factors for nitrogen oxides, as published by Defra (in its Emissions Factors Toolkits (EFTs) V6 and V7), and those measured in the real world.  CURED Versions 1A and 2A were produced following a detailed review of real-world emissions factors carried out by Air Quality Consultants.  They worked by calibrating the ‘official’ emissions factors, at that time based on emission functions from COPERT V4.10 and V4.11, against measured data.

Defra recently released a new version of its EFT (V8.0.1), which now uses emissions functions from the COPERT V5 model.  Air Quality Consultants has previously compared the COPERT V5 functions with those contained in the CURED V2A model.  For the current fleet of diesel cars and vans, COPERT V5 agrees closely with CURED V2A.  However, COPERT V5 (and thus EFT V8.0.1) also assumes that those diesel cars and vans manufactured in the future will perform better than those that have currently been tested, which are captured within CURED V2A.

Unlike in the past, where there was evidence showing that EFT V6 and EFT V7 under-predicted emissions from the latest diesel cars and vans, the position for EFT V8 is that its predictions for existing vehicles are a reasonable match to real-world emissions.  The key remaining questions relate to the performance of future vehicles (which are currently untested) and the projections regarding how quickly these vehicles, and other technology types, will populate the fleet.

Air Quality Consultants has reviewed the evidence and considers that there are now reasons to now be optimistic about future NOx emissions.  There are, however, still sources of uncertainty and so it seems prudent to continue to apply a CURED sensitivity test to allow for the possibility that EFT V8.0.1 is over-optimistic. 

CURED V3A follows most of the same assumptions as EFT V8.0.1, but simulates the failure of post-2020 diesel cars and vans to provide any improvement over those that are currently entering the fleet.  The figure below shows how EFT V7.0, EFT V8.0.1, CURED V2A, and CURED V3A predict emissions per vehicle might change over time normalised to a 2016 base year.  More details on the development of CURED V3A are provided here. 

UPDATED-CURED-TO-V3A-Figure.jpg



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