National low emission framework

Methodology for local authorities to undertake air quality assessment through the National Low Emission Framework (NLEF) to inform decisions on transport-related actions.

1. Introduction

1.1 Purpose

1.1.1 The National Low Emission Framework (NLEF) is an air quality-focused, evidence-based appraisal process developed to help local authorities consider transport related actions to improve local air quality, where transport is identified as the key contributor to air quality problems.

1.1.2 The NLEF supports and builds on the work already being done through the Local Air Quality Management (LAQM) system.

1.1.3 Local authorities in Scotland should have regard to NLEF when undertaking their local air quality management duties, as required under section 88(2) of the Environment Act 1995.

1.1.4 Local authorities that have declared Air Quality Management Areas (AQMAs) should have regard to the NLEF when developing their air quality action plans.

1.1.5 The guidance should be considered in conjunction with the LAQM Policy Guidance PG(S)(16) and LAQM Technical Guidance TG(16).

1.2 Context

1.2.1 The vision set out in Cleaner Air for Scotland – The Road to a Healthier Future (CAFS) is for Scotland to have the best air quality in Europe and to protect and enhance health, wellbeing and the environment and ensure placemaking and sustainable economic growth are supported by improved air quality across Scotland.

1.2.2. The NLEF will contribute to this by assisting in the consideration of actions that will reduce the impacts of pollutants such as nitrogen dioxide (NO2) and particulate matter (PM) in a way that supports public health and the local economy, making urban areas more attractive places to live, work, do business and spend leisure time.

1.2.3 The NLEF also has a correlation to the National Transport Strategy key strategic outcomes, which has a particular focus on reducing emissions to tackle climate change, air quality, health improvement, along with cross-over to elements such as congestion and accessibility.

1.3 Aims and objectives

1.3.1 The primary aim of the NLEF is to improve local air quality in areas where Scottish Air Quality Objectives (AQOs) are exceeded, or likely to be exceeded, and transport is identified as the key contributor.

1.3.2 It may not be feasible to remove an exceedance of an AQO in a particular area through implementing any individual action identified through the NLEF appraisal process. The process will, however, support the consideration of actions that could reduce the magnitude, extent or timescale required to remove an exceedance.

1.3.3 The focus of any action considered under the NLEF should be on the particular pollutant or pollutants which exceed Scottish AQOs in an AQMA. Whilst an action focused on reducing NO2 would also potentially result in a reduction in PM10 and PM2.5 concentrations, this should be considered a secondary benefit, rather than an absolute requirement. Care will, however, be required to ensure that actions do not have the unintended consequence of increasing levels of non-target pollutants.

1.3.4 Whilst actions to improve air quality could potentially result in a reduction in CO2 emissions due to vehicle owners switching to electric vehicles or to other modes of transport, reducing CO2 emissions is not a primary objective or requirement of actions being considered under the NLEF appraisal process. Local authorities are, however, encouraged to consider whether actions identified through the NLEF appraisal process can help support reductions in emissions of CO2 within their areas where possible; e.g. by encouraging active travel and supporting the uptake of low emission vehicles so that benefits in both local air quality and emissions of greenhouse gases are realised together.

1.4 Roles and responsibilities

1.4.1 This guidance has been developed to support local authorities but is relevant to a range of organisations, including the Scottish Environment Protection Agency (SEPA) and the Scottish Government, who have an overseeing role to play in improving local air quality.

1.4.2 The NLEF appraisal should be a collaborative process between a range of local and national bodies.

1.4.3 Within local authorities a collaborative approach will be required, encompassing transport planning, traffic engineering, environmental health, sustainability, planning and legal and finance specialists. Input from those who have implemented transport schemes and those with air quality expertise will be key to ensuring that the NLEF appraisal process is undertaken in a robust manner.

1.4.4 Stage one of the NLEF process, the screening exercise, will be undertaken by local authorities using existing data, compiled as part of existing LAQM review, assessment and action planning duties and incorporating consideration of wider land use and transport planning work. Stage two, the assessment process, will be carried out by local authorities supported by SEPA through the National Modelling Framework (NMF).

1.5 National Low Emissions Framework and Local Air Quality Management

1.5.1 The NLEF is intended to support and complement the existing LAQM system which is already well defined and developed. Those local authorities with declared AQMAs are required to develop an air quality action plan within one year of declaration. This details the measures identified by the local authority as contributing to meeting the air quality objectives in the future.

1.5.2 The relationship between the LAQM system and the NLEF appraisal process is illustrated in the flowchart included as Figure 1 below.

1.5.3 The NLEF process will be undertaken by all local authorities with an AQMA where transport emissions are the primary reason for declaration and should form part of future air quality action planning. Results of the NLEF screening and, where appropriate, assessment processes will be reported in the Annual Progress Report (APR) submitted by local authorities in June of each calendar year.

1.5.4 The air quality action plan will also be updated with these findings and the proposals for measures to be implemented.

Figure 1 – Relationship between NLEF and LAQM system

Figure 1 – Relationship between NLEF and LAQM system

1.6 National Modelling Framework

1.6.1 The National Modelling Framework (NMF) is a key strand of CAFS which will develop a national, two-tiered modelling approach for air quality within Scotland. The NMF aims to standardise data collection requirements, analysis processes and presentation of outputs to provide local authorities with information required to appraise measures for improving urban air quality.

1.6.2 The development of regional NMF models will support decision-making around placemaking and transport planning in relation to air quality management across city regions.

1.6.3 Local NMF models will represent a standardised approach to modelling air quality for local authorities undertaking a stage two NLEF assessment. The focus will be on identifying detailed traffic-related source apportionment across the appropriate area, with the outputs providing quantitative evidence to support decision-making, including on the potential benefits of introducing a Vehicle Access Restriction Scheme (VARS) to improve air quality.

1.6.4 It is expected that local NMF models will provide a significant proportion of the quantitative evidence required within the NLEF appraisal process, producing outputs and visualisation tools to aid decision-making.

1.6.5 In addition, the NMF will link traffic model outputs and air quality modelling, allowing local authorities to consider wider traffic management measures in the context of improving local air quality.

1.6.6 The NMF approach ensures that the analysis and generation of evidence to support decision-making is consistent across Scotland despite transport issues and sources of emissions differing between geographical areas.

1.7 Low Emission Zones

1.7.1 Cleaner Air for Scotland set out a number of measures for consideration as part of the NLEF, including Low Emission Zones, Clean Air Zones (as defined by the City of York in relation to buses, rather than as defined by Defra through work in the National Air Quality Action Plan), other Access Regulation Schemes, Traffic Management and Vehicle Licensing Regulations. With the exception of traffic management and vehicle licensing, all aim to restrict vehicles within a geographical zone, with the type of vehicles subject to restrictions dependent upon the objective set. For example, bus lanes generally restrict vehicles other than buses and taxis in order to improve the efficiency of bus operations.

1.7.2 In relation to improving air quality, in Clean Air Zones and Low Emission Zones the restrictions imposed are generally based on an emission standard. As such, these definitions have been brought together and will be referred to as Low Emission Zones (LEZs) throughout this document.

1.7.3 Scottish LEZs will be based on VARS which allow the exclusion of vehicles that do not meet the relevant criteria within a defined geographical area. The relevant criteria will be based on a nationally agreed standard for emissions. Once an LEZ has been declared, affected vehicles would be required to meet the relevant emission standard in order to enter the designated area. Any vehicle not meeting the relevant emission standard (other than those exempt from the requirements) would be subject to a financial penalty.

1.7.4 LEZs are primarily intended to ensure the use of more polluting vehicles is reduced and that those vehicles which enter the zone meet more stringent emissions standards. The potential benefit comes from the reduction in emissions associated with vehicles. LEZs may also encourage consideration of modal shift to public transport and active travel with the potential for fewer vehicles overall to enter the zone.

1.7.5 There is the potential for vehicle access restrictions introduced for reasons other than air quality and other traffic management measures, such as changes to traffic light sequencing, to help improve air quality. It is anticipated that these options will be considered as part of stage one of the NLEF appraisal process. The NMF approach at stage two, whilst focusing on consideration of LEZs, will also provide information to support local authorities in considering a range of other transport-related actions.

1.7.6 This document does not include discussion of road access charging (i.e. zones which vehicle owners would be charged to access). The Scottish Government is committed to any vehicle access restrictions put in place to support air quality improvements being introduced on a penalty basis in order to incentivise compliance.

1.7.7 The NLEF approach will support:

  • consideration of options that reflect specific, localised situations
  • targeting locations where exceedances of air quality criteria are occurring or are likely to occur
  • flexibility for local authorities to influence the specific vehicle class or classes that are the primary contributors to poor air quality in their area

1.7.8 The NLEF appraisal process will assist local authorities to determine whether an LEZ is appropriate to address air quality issues in their area. Where it is determined that an LEZ is an appropriate option, the process will help local authorities to define the boundary of the zone and to consider the scope of the vehicle classes to be included in order to achieve the air quality improvements required.

1.7.9 All vehicle types should be considered for inclusion in an LEZ and be assessed as part of the NLEF appraisal process. Depending upon the outcome, a single vehicle type or a combination of vehicle types could be subject to the LEZ requirements.

1.7.10 Generally, the more vehicle classes which are included in an LEZ then the greater the associated potential for improvement in local air quality. It will be particularly important to consider the scale of the air quality exceedances and the vehicle types which are making the most significant contribution as a key consideration in determining the requirements of any individual LEZ.

1.7.11 Further information on Low Emission Zones can be found in Appendix 2.


Email: Andrew Taylor

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