How effective will the ULEZ be?

A map showing levels of nitrous oxide. They are high almost everywhere, particularly in central London, around Heathrow airport and along the North Circular Road and other major dual carriageways.
London’s nitrous oxide levels today

This April a new low-emission zone, the Ultra Low Emission Zone (ULEZ), will take effect in central London. This will mean that drivers or owners will have to pay a charge to drive a vehicle over a certain age into the area; the charge will apply to any diesel car, van, truck or bus with older than Euro 6 emission ratings (which started to be sold in early 2014) and any petrol car with older than Euro 4 ratings (which were the norm from early 2005 although they had been available since 2001). From 2021, the zone will expand to include the area bounded by the North and South Circular Roads, which is a much larger area, especially north of the river. Today, Labour councillor and assembly member Tom Copley published maps showing London’s air quality today and its predicted quality by 2025, which suggests that nitrous oxide levels in inner London will fall to levels currently only seen right on the edge of town (Euro 6, unlike previous revisions to European emissions criteria, is particularly concerned with filtering nitrous oxides). I am a bit sceptical.

Currently, London has a low emission zone (LEZ) which bars vans and trucks from entering most of Greater London unless they have an emission rating of Euro 4 or better; the vehicle can be driven in but the owner must pay a £200 charge per day. The upshot is that few companies anywhere near London still operate these trucks and, obviously, instruct drivers never to drive them into London and do not allocate them to London runs if they do. The new zones will have a £100 daily charge for trucks and a £12.50 charge for cars and vans. Clearly, this will mean very much fewer trucks with high nitrous oxide emissions being driven into inner London, although the price may well be worth it for operators of vans of up to 3.5T. However, the map suggests a very much reduced NOx emission level in outer parts of London, which I suggest is exaggerated.

This is for two reasons. First, the North Circular Road is a very good quality road, mostly dual carriageway and three lanes in each direction for most of its length, apart from some poor quality sections around Ealing, Golders Green and Wood Green where it has not been upgraded and there are currently no plans to do this. It remains a more direct route to use this road to get from east to west London than the M25 and the time saved is even greater if the M25 is also congested. In such circumstances, people may drive in as far as the North Circular as many of the roads in are fast dual carriageways (e.g. the A13 and A40) or motorways (such as the M11 and M1) and the distance to the M25 is often quite short, especially on the north side.

A map showing predicted nitrous oxide levels in 2025. Levels have fallen to about a third of today's, though central London and Heathrow airport still have higher levels than elsewhere.
Predicted nitrous oxide (NOx) levels in London in 2025, after the ULEZ has expanded to the North & South Circular Roads

Second, the area bounded by the South Circular is very much smaller than that bounded by the North Circular; there is a very large area of what is generally considered as inner London such as Streatham, Tooting (Sadiq Khan’s old constituency) and Crystal Palace which lie away from the South Circular Road as well as the traditional old Surrey and Kent suburbs. Similarly, there are large tracts on the east and west sides of London which are outside the circular roads. The South Circular Road is a slow, very congested road that passes through several shopping areas (Sheen, Putney, Wandsworth, Catford) and has low bridges and other hazards. Unlike the North Circular Road, it was not built as a by-pass but is a series of local main roads that were renumbered and that explains the twists and turns, the numerous local names and the odd shape. Companies will still use older trucks to make deliveries in the outer areas as there is plenty of industry there, and as companies with both types of vehicles redeploy their vehicles to take account of the new charges, more older trucks will be used for outer-suburban deliveries while the newer ones are sent further into town, which may mitigate the reductions for a few years (over time, companies renew their fleets anyway, but smaller companies still using Euro 4 and 5 trucks will not want to trade them in for Euro 6 trucks as they have lower payloads and higher maintenance costs).

This is not to say the new rules are a bad thing, as Euro 6 has been around for a few years now, most manufacturers have produced a second generation of trucks which ironed out the reliability problems of the first, and early Euro 6 models have come down in price after coming off lease. But the benefits to those of us in the outer suburbs are rather overstated, in my opinion, as not all the traffic which thunders through every day is going to inner London, much less the central area; a lot of it stops and starts locally, and none of that will be affected by the new zone.

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