The AIR Index – Van Ratings for Urban NOx

The AIR Index urban NOx ratings were launched in February 2019 based on test data collected in accordance with the CWA17379 methodology developed for cars and light-duty vehicles (vans). The AIR Index ratings provide trusted, independent and comparable insight to inform vehicle choice and policy decisions based on the actual NOx emissions produced during urban driving. The initial programme of testing focused on cars and the next step is the publication of the AIR Index NOx ratings for vans.

In consultation with AIR’s Scientific Advisory Committee (SAC), AIR re-examined the CWE17379 testing methodology to consider the correlation between payload and NOx emissions, which is not necessarily a linear relationship, to avoid the risk of distortion when the results are translated to an AIR Index rating for vans.

As a result of the consultation and following advice from AIR’s expert advisors, the collection of data for vans (vehicle category N1 in Class I, II, III) to be rated in the AIR Index must include additional tests, based on two payloads. The highest NOx emissions level recorded from either test will be used as the basis for the AIR Index rating and subsequent publication of the results. All testing is conducted according to the CWA17379 methodology, and this amendment to include two tests at different payloads will be included in the review and revision of the methodology at the next CEN workshop.

This document presents the results from the first programme of van testing, which included Euro 6 pre-RDE in N1 classes I, II and III. The ten models tested represent approximately 50% of all new vans sold in Europe in 2017* which is the most recently available public data on van registrations by make and model.

Relationship between payload and NOx emissions

The CWA17379 standard methodology explicitly includes N1 light duty vehicles, and describes the boundary conditions for the vehicle mass in Section 6, see extract below:

The tests commissioned by AIR were undertaken in two conditions:
(i) unladen (‘Mass in running order’)
(ii) laden with 90% of gross vehicle weight (same as RDE max condition)

*source ICCT European Market Report 2017

Results of vans tested

(all Euro 6, pre-RDE unless otherwise stated)

Light Vans – N1 Class I

Medium Vans – N₁ Class II

Large Vans – N₁ Class III

The average difference in NOx emissions recorded according to the CWA17379 standard method between unladen and laden is variable (see ‘Laden Premium’ column).

We will continue to test with the ‘Mass in running order’ as per the CWA17379 standard methodology AND by applying the 90% of gross vehicle weight.

We have observed that some vans produce higher levels of NOx emissions laden, and others unladen, therefore we will use the worse result from the tests with different masses applied as the basis for the banding, since the vehicle could be used in either condition during urban driving.

The first AIR Index urban NOx ratings for vans were published during November 2019.