The launch of the Ultra Low Emission Zone (ULEZ)in London is a necessary step on the road to cleaning up urban air quality but will not stop ‘dirty diesels’ from entering the capital despite controlling access based on emissions.
London’s policy has ambitious scope, is complemented by action on other vehicles such as buses and trucks, and avoids outright bans by using a charging mechanism to create an efficient mechanism to abate nitrogen oxide (NOx) emissions.
Allow Independent Road-testing (AIR), the publishers of the AIR Index, the world’s only fully independent, standardised on-road emissions rating system, which gives cars a rating based on their actual urban NOx emissions, has already warned that using Euro emissions standards are a poor proxy for urban emissions, as many vehicles emit way in excess of accepted limits.
Under the ULEZ scheme, penalty-free access to the centre of London will only be granted to petrol cars with a minimum Euro 4 standard while diesels must comply with the Euro 6 standard. These apparently different limits are in fact logical as they both equate to 80 mg/km of NOx. But tests conducted for AIR and rated in the AIR Index show that many Euro 6 diesels will legitimately still be producing many times the officially published NOx limit, with free access to ULEZ.
The Euro standards are the officially accepted levels of emissions recorded during tests conducted mainly by car makers themselves, on their own products and until recently entirely in laboratory conditions. However, emissions recorded during on-road driving in urban conditions, including stop-start in traffic, bear little resemblance to the emissions recorded during laboratory tests where vehicles can be optimised to achieve specific results.
When a 2017 Renault Clio 1.5 litre dCi diesel was tested and rated in the AIR Index, it emerged that the supermini emitted 20 times more NOx in urban driving than a 2018 Land Rover Discovery 3.0 litre TD6 diesel, yet both fall under the category of ‘Euro 6’. What’s more, some Euro 6 diesels produce more urban NOx than earlier, cleaner Euro 5 vehicles. The results of variations between Euro 6 vehicles was presented at the launch of the AIRIndex inFebruary 2019.
Following Dieselgate, Euro 6 was tightened up, but rather than issue a new Euro 7 standard, Euro 6 has continued to be used but with suffixes. It now (confusingly) straddles a wide spread of permitted emissions.
Whilst the latest phase of the Euro 6 standard – in this case 6d which includes on-road testing - does set low levels of urban NOx emissions, millions of cars with a pre-Euro 6d standard have been sold across Europe and some are still on sale today. All these have unlimited ULEZ access since they fall within the overall Euro 6 stage.
The AIR Index rates vehicles tested in urban conditions to the same standardised methodology providing comparable NOx emissions levels that more accurately reflect the contribution to urban air quality than existing tests performed in a laboratory.
It has been created to inform and empower car buyers and city policy makers with the real facts about vehicle emissions when making choices about car purchase and usage. A simple A-E colour-coded rating, shows the difference between clean and dirty vehicles based on how much NOx comes out of a car’s tailpipe in urban driving.