Clean Air Zones, Low Emission Zones and the London ULEZ

Overview

In recent years the following road user charging zones have been introduced in parts of the UK:

• London’s low emission zone (LEZ) and ultra low emission zone (ULEZ),
• England’s clean air zones (CAZ), and
• Scotland’s low emission zones (LEZ).

These zones are intended to reduce air pollution in cities by charging drivers of older, more polluting vehicles to enter them.

These zones’ rules are all based on the Euro emission engine classification standards. In any of the zones, vehicles meeting the following standards will be compliant and not be subject to any charges:

• Euro 4 for petrol cars and vans (generally vehicles registered from 2006)
• Euro 6 for diesel cars and vans (generally vehicles registered from September 2015)
• Euro VI for buses, coaches and HGVs (generally vehicles registered from January 2013)

Non-compliant vehicles are charged for entry. Non-payment of charges attracts penalties. The types of vehicles included, exemptions, and rates of daily charges and penalties differ between different types of zone.

Charging for road use in England: Origins and legislative basis

The ability for local authorities in England and Wales to charge road users is set out in part III of the Transport Act 2000. The Mayor of London has powers to introduce “road user charging” across all Greater London or some parts of it, under section 295 of the Greater London Authority Act 1999. The charging provisions in the 1999 Act and in the Transport Act 2000 are broadly similar.

Since 2003, successive Mayors in London have used the powers granted by the 1999 Act to introduce congestion charging, low emission zones and the ultra low emission zone.

Road user charging outside of London has only been introduced much more recently, particularly since the Government’s publication of the 2017 UK Plan for Tackling Roadside Nitrogen Dioxide Concentrations, which itself followed several legal challenges to the Government over air quality.

Since 2017, the Government has used its powers under the Environment Act 1995 to ‘direct’ many local authorities to produce clean air plans. Local authorities can then charge drivers using powers granted by the 2000 Act.

Clean Air Zones in England

There are currently seven cities charging under clean air zones in England: Bath, Birmingham, Bradford, Bristol, Portsmouth, Sheffield, and Tyneside (Newcastle and Gateshead). Daily entry charges for non-compliant vehicles range from £7 for taxis in Bradford, to £100 for lorries, buses and coaches in Bristol.

Greater Manchester’s Clean Air Zone scheme is under review.

London’s ULEZ and LEZ

London has had a low emission zone for larger vehicles like buses, lorries and coaches, since 2008. It has been gradually expanded to cover all London boroughs. Daily LEZ charges for non-compliant vehicles are between £100 and £300.

In 2014 Boris Johnson, then Mayor of London, announced plans for an ultra low emission zone (ULEZ) which was introduced by his successor Sadiq Khan in April 2019, and applies to more vehicle types, including cars, motorcycles and vans. In October 2021 the ULEZ expanded to cover the area between the North and South Circular roads. The ULEZ charge is currently £12.50 per day for non-compliant vehicles.

On 25 November 2022, the Mayor announced that the ULEZ will expand again on 29 August 2023, to cover all London boroughs. The expansion decision was subject to a judicial review brought by five Conservative-led councils but the High court dismissed their case in July 2023.

Low emission zones in Scotland

In Scotland, low emission zones (LEZs) were introduced in May 2022, in Glasgow, Edinburgh, Dundee and Aberdeen. Only Glasgow’s LEZ is being enforced so far. Enforcement in Glasgow commenced on 1 June 2023, and is due to commence in the other cities in May and June 2024.

A key difference between LEZ scheme in Scotland and CAZ and ULEZ schemes in England is that LEZ schemes in Scotland do not allow non-compliant vehicles to enter at any time; there is no option to pay a daily charge. Drivers who enter the LEZ in non-compliant vehicles must pay a penalty of £60 a day.

The Transport (Scotland) Act 2019 provides the legal basis to enable the creation and civil enforcement of LEZs in Scotland.

Clean air zones in Wales

There are currently no charging clean air zones in Wales, and no plans for any. The legislation enabling the creation of clean air zones in England, Part III of the Transport Act 2000, applies to Wales as well.

In 2019, Cardiff Council decided that a CAZ in Cardiff was not necessary to meet its clean air plans, a decision that the Welsh Government accepted.

However, in April 2023 Cardiff Council said they were re-visiting the issue due to concerns over carbon emissions, air pollution and associated health risks in the city.

There is currently no legislation that allows for road user charging in Northern Ireland.

National road user charging

In 2022, the Transport Select Committee published its report into road pricing (PDF). This noted that the expected transition to electric vehicles will reduce tax revenues from vehicle excise duty and (especially) fuel duty, and it recommended the Government start work on a national road pricing system.

The committee report noted that there is currently a ‘patchwork’ of local road pricing mechanisms which may make it more difficult to introduce a national scheme, but that it was nevertheless important that the Government start work on a national road charging scheme urgently.

HM Treasury responded to the report by letter on 9 January 2023, saying “the Government does not currently have plans to consider road pricing.”

The air quality context

Road vehicles are sources of air pollutants such as particulate matter and nitrogen dioxide (NO2). Exposure to these pollutants can be harmful to human health, the severity of which can vary depending on the nature and duration of exposure. In 2022 the Chief Medical Officer summarised that air pollution is, “associated with impacts on lung development in children, heart disease, stroke, cancer, exacerbation of asthma and increased mortality, among other health effects.”

Legal air quality standards

There are several legal limits and targets in place for air quality, which stem from international agreements, retained EU legislation and domestic legislation.

The Air Quality Standards Regulations 2010 set limits for concentrations of specific pollutants which must not be exceeded. Under part IV of the Environment Act 1995, local authorities are required to regularly review and assess air quality in their areas against these limits.

Judicial review and the requirement to comply “in the shortest possible time”

The breach of air quality limit values for NO2 have been the subject of a series of judicial review proceedings brought by the environmental advocacy charity, ClientEarth. Following judicial review challenges in 2015, 2016 and 2017, the UK Government was directed by the courts to produce a series of plans to show how it would reduce NO2 “in the shortest possible time.” The most recent, and still current, plan is the UK plan for tackling roadside nitrogen dioxide concentrations: Detailed plan, July 2017.

Under this plan, the UK and Welsh Governments have identified local authorities that do not comply with NO2 limits and issued ‘Directions’ under the Environment Act 1995 to require them to demonstrate how they will remedy this.

Consideration of clean air zones

To comply with such a Direction, a local authority must consider the establishment of a clean air zone. This is because a clean air zone will often be the most effective way to deliver compliance, in the shortest possible time. However, it could also take other measures such as building bypasses, reducing speed limits, and retro-fitting buses with cleaner technology. Government funding has been granted to local authorities to assist with this work.

Impact of clean air zones on air quality

It can be difficult to assess the effectiveness of just one action alone on air quality. This is because many different factors, such as weather patterns, can affect air quality levels at any time. A small number of studies, however, have attempted to examine the evidence available. While a few studies have highlighted a reduction of air pollution after the introduction of clean air zones, this sits in the context of a general longer-term downward trend in air pollutants, influenced by other factors, such as improvements in vehicle emissions standards.