Engine Idling Investigation Improvement Report

2.1
ESS was established under the UK Withdrawal from the European Union (Continuity) (Scotland) Act 2021 (‘the Continuity Act’)[8] to fill the environmental governance gap caused by the UK’s departure from the European Union. ESS is an independent body, accountable to the Scottish Parliament. The role of ESS is to ensure there is effective scrutiny of public authorities’ compliance with environmental law, alongside the effectiveness of environmental law and the way it is being implemented and applied in Scotland. ESS may investigate matters in response to concerns brought to its attention (known as representations), or on its own initiative.

2.2
ESS’ remit covers a broad range of environmental law, including all aspects of environmental protection and harm, particularly in relation to human beings and their enjoyment of the environment. All public authorities, including the Scottish Government and its agencies, as well organisations carrying out functions of a public nature, fall within the remit of ESS. Public authorities are under a duty to cooperate with and assist ESS, and to try to swiftly resolve any matters that ESS raises with them. The Continuity Act provides ESS with powers to:

• issue an information notice requiring a public authority to provide ESS with any information ESS requires to carry out its functions
• issue a compliance notice requiring a public authority to take the steps specified in the notice to address its failure to comply with environmental law (and to prevent that failure and the environmental harm associated with it from being repeated in the future)
• issue an improvement report where ESS considers that the actions of a public authority have failed to comply with environmental law, make effective environmental law, or implement or apply environmental law effectively
• make an application for judicial review (or apply to the court for permission to intervene in civil proceedings) where ESS considers that the conduct of a public authority constitutes a ‘serious’ failure to comply with environmental law and it is necessary to prevent, or mitigate, ‘serious’ environmental harm
• make recommendations in relation to any matter relevant to ESS’ functions

[8] UK Withdrawal from the European Union (Continuity) (Scotland) Act 2021

3.1
Vehicle idling (even for short periods) can generate disproportionate emissions; research indicates that vehicles left idling for as little as 30 seconds can produce significantly higher emissions than switching engines off and restarting[9]. Engine idling contributes to emissions of nitrogen oxides (NO_X) and fine particulate matter (PM₅), both of which are known to have significant adverse effects on human health. These pollutants are associated with respiratory and cardiovascular disease and contribute to long‑term illness and premature mortality. PM_2.5 is particularly harmful because particles are small enough to penetrate deep into the lungs and enter the bloodstream[10]. Recent assessments indicate that long‑term exposure to outdoor air pollution contributes to an estimated 1,800 to 2,700 deaths annually in Scotland[11].

3.2
Evidence also demonstrates that exposure to NO₂ and PM₅ is not evenly distributed across the population. Within Scotland’s urban areas, people living in income‑deprived neighbourhoods, people from minority ethnic backgrounds, people with mental‑health conditions and people living in rented accommodation are more likely to experience higher than average concentrations of these pollutants which exceed WHO guidelines[12]. Vehicle idling is a preventable source of localised air pollutant emissions which can contribute to elevated pollutant concentrations in locations where vulnerable populations are more likely to be exposed.

3.3
Recent research[13] has found that air quality monitoring is unlikely to reflect the on-site conditions at many schools in Scotland given the significant distances from monitoring sites. Pollution from short‑lived and episodic sources, such as vehicle queuing and idling associated with drop‑off and pick‑up activity, may therefore be under‑represented.

3.4
The Scottish Government’s public communications recognise the health impacts associated with vehicle idling, noting that it ‘creates harmful air pollution – a major threat to human health’[14] and that ‘even low pollutant concentrations can impact a wide range of both short and long term health conditions’[15].

3.5
Although Scotland has seen an improvement in air quality, ongoing and increased action will be required to maintain and build on this progress. This is particularly the case in the context of the Scottish Government’s stated ambition to take continued action to drive down pollution levels still further.

[9] TRL Engine Off Summary Infographic – Final.pdf

[10] Air quality, energy and health

[11] Chemical hazards and poisons report: issue 28

[12] Air Pollution and Inequality in Scotland: Examining Differences in Pollutant Concentrations across Scottish Neighbourhoods

[13] Proximity of city schools in Scotland to air quality monitors: an exploratory geomapping study in five Scottish cities | BMJ Public Health

[14] Vehicle Engine Idling: Switch Off When You Stop, June 2025

[15] Environmental Standards Scotland air quality investigation – Scottish Government improvement plan

4.1
Stationary engine idling in Scotland is controlled through multiple, interacting provisions:

• Regulation 98 of the Road Vehicles (Construction and Use) Regulations 1986 (as amended)[16] requires drivers to switch off the engines of their vehicles when stationary to prevent noise or exhaust emissions
• Section 42 of the Road Traffic Act 1988[17] makes contravention of Regulation 98 of the 1986 Regulations (stationary idling) a criminal offence
• the 2003 Regulations provide powers to ‘authorised persons’ (a person authorised by a designated local authority) to regulate engine idling

4.2
Under Regulation 12(1) of the 2003 Regulations an authorised person who has reasonable cause to believe a ‘stationary idling offence’ is being committed, may require the driver to turn off their vehicle engine. A driver who fails to comply with this requirement is guilty of a criminal offence (Regulation 12(2)) and liable on summary conviction to a fine not exceeding level 3 on the standard scale (currently £1,000).

4.3
Regulation 13 of the 2003 Regulations enables an authorised person who considers that a ‘stationary idling offence’ has been committed to issue a FPN to the driver of the vehicle. The current penalty amount is set at £20 (Regulation 8(b)).

4.4
In 2003, the Scottish Government issued statutory guidance under Section 88 of the Environment Act 1995[18]. The purpose of the statutory guidance was to provide day-to-day operational guidance to authorised persons when exercising their functions under the 2003 Regulations, including the use of enforcement powers.

[16] The Road Vehicles (Construction and Use) Regulations 1986

[17] Road Traffic Act 1988

[18] Environment Act 1995

5.1
The representation raised concerns that the statutory guidance was restricting how local authorities used enforcement powers. It was suggested that references to FPNs being used only as a ‘last resort’, limited the circumstances in which FPNs could be used and were associated with low levels of enforcement and variation in practice across local authorities.

5.2
In order to understand how the statutory guidance on vehicle idling was being interpreted, applied in practice and the extent to which it influenced enforcement activity, ESS sought information from the four major urban local authorities in Scotland (City of Edinburgh, Glasgow, Dundee and Aberdeen). This included data relating to complaints and enforcement activity (including in the context of Low Emission Zones), the use of alternative intervention measures such as warnings or educational approaches, any local policies or procedures relating to vehicle idling enforcement, as well as any data or evidence held on the deterrent effect of FPN levels.

5.3
The responses received highlighted several recurring issues, including:

• misunderstandings arising from the guidance, such as the view that officers must always issue a warning or allow additional time before issuing an FPN; this appeared to arise from wording in the guidance suggesting that FPNs should be used only as a ‘last resort’
• the view held by some authorities that a Regulation 12 instruction must always precede the issuing of a Regulation 13 FPN

5.4
On review of the available evidence, ESS concluded that, while local authorities are responsible for deciding how best to use enforcement powers, the statutory guidance did not provide sufficient clarity to support consistent and effective enforcement. In particular, the guidance:

• contained ambiguous information about when and how enforcement could take place
• created uncertainty around exemptions by blurring the distinction between legal requirements and discretionary judgments, such as references to ‘common‑sense’ decisions or ‘mitigating circumstances.’ This created a risk that officers could not clearly determine when an exemption applied as a matter of law and when discretion was intended to be exercised
• failed to clearly set out the two distinct offences, namely the failure to comply with a direction to switch off an engine (a criminal offence under Regulation 12) and the separate stationary idling offence for which a FPN may be issued under Regulation 13

5.5
In ESS’ view, the above issues risked incorrect enforcement practice and undermined the intended function of the regulatory framework for managing engine idling and reducing unnecessary emissions. Accordingly, ESS recommended that the statutory guidance should be reviewed and updated to address in particular, but not necessarily limited to, the above points and deliver clear, comprehensive, and unambiguous guidance to authorised persons to facilitate the effective and proportionate use of enforcement powers.

5.6
The Scottish Government accepted ESS’ recommendation, and revised statutory guidance was published on 5 March 2026[19].

5.7
ESS has reviewed the revised statutory guidance and notes that references to FPNs being used only as a ‘last resort’ have now been removed. ESS considers that this change addresses a key source of ambiguity identified during the investigation, thereby reducing perceived barriers to the use of enforcement powers and providing clearer direction to local authorities.  ESS also considers that the revised guidance provides greater clarity regarding the distinction between legal pre-requisites and the exercise of discretion, as well as clearer explanation of the two separate idling offences. Accordingly, ESS considers informal resolution of this issue to have been achieved.

[19] 2. Vehicle idling enforcement – How to use the powers – Vehicle idling: guidance for local authorities – gov.scot

6.1
The representation raised concerns about the recording and reporting of stationary engine idling enforcement activity by local authorities. In particular, it was suggested that the absence of consistent and comparable reporting, including the non‑submission of six-monthly returns to the Scottish Government as envisaged by the original statutory guidance, limited transparency and made it difficult to understand how enforcement powers were being used in practice. Concerns regarding limited transparency and the absence of national oversight have also been raised through parliamentary processes, including Public Petition PE1944[20], indicating wider stakeholder and public concern about the effectiveness of current arrangements.

6.2
The statutory guidance set out an expectation that local authorities would record the use of stationary engine idling enforcement powers. The guidance stipulated active and regular reporting by local authorities, stating that a standard form should be completed by all local authorities every six months and forwarded to the Scottish Government. The purpose of this requirement was to support national oversight of the enforcement regime, enabling Scottish Ministers to monitor how the 2003 Regulations were being applied in practice and to assess the consistency and effectiveness of enforcement activity.

6.3
ESS found that no national monitoring or reporting of enforcement activity is taking place. Although some local authorities hold internal records of enforcement activity, these systems vary significantly and lack standardisation. As a result, the information available consists of a combination of complaints data, informal reports, and anecdotal accounts, none of which provide a reliable or comprehensive basis for assessing enforcement activity or compliance trends. Complaints relating to vehicle idling are also recorded in different forms across local authorities, limiting their comparability and making meaningful interpretation challenging.

6.4
The Scottish Government acknowledged these inconsistencies but emphasised that local authorities maintain their own internal systems and that it does not consider centralised reporting to be necessary. The Scottish Government explained that the available evidence suggests drivers are generally compliant and switch off their engines when asked, and that the absence of centralised reporting did not therefore indicate operational failure. No supporting evidence was cited in support of this position. The Scottish Government also noted that establishing a mandatory, standardised reporting mechanism would place an administrative burden on local authorities and indicated that it intends to explore the sharing of case studies and examples of local monitoring as part of its next phase of work, rather than pursuing national standardised reporting.

6.5
Whilst acknowledging the Scottish Government’s position, ESS considers that the absence of consistent and comparable data across local authorities limits the ability to assess the scale of vehicle idling activity, to evaluate how the 2003 Regulations are being implemented in practice, and to determine whether the statutory regime is functioning as intended.

6.6
ESS intends, on a time‑limited basis, to issue a request to all local authorities requiring them to provide annual data on engine idling offences and associated enforcement activity. The exercise is intended to address the current evidence gap and the information gathered will be used by ESS to undertake an assessment of the operation and effectiveness of the 2003 Regulations.

[20] PE1944 Enforce engine idling ban | Scottish Parliament Website

7.1
The representation raised concerns that the current £20 FPN for stationary engine idling offences is too low to act as an effective deterrent and does not reflect the environmental and public health harms associated with the practice. It also suggested that the comparatively low level of the penalty may discourage enforcement.

7.2
ESS considers that in order for an enforcement penalty to be effective, it must have clear deterrent value, be publicly visible and consistently enforced. These principles are echoed by the findings of the Scottish Government’s Fly Tipping Prevention Review[21].

7.3
In their evidence to ESS, local authorities set out that:

• the current £20 fine is too low and unlikely to influence driver behaviour
• the penalty compares unfavourably with other transport and environmental related penalties
• the administrative cost of issuing a FPN often exceeds the value of the fine, creating a practical disincentive to take enforcement action

7.4
Parliamentary scrutiny has also highlighted the limited use of FPNs for engine idling offences. In considering Public Petition PE1944, the Scottish Parliament’s Citizen Participation and Public Petitions Committee was advised that FPNs for idling were rarely, if ever, issued[22].

7.5
Further evidence gathered through ESS’ investigation has found that:

• the penalty level has remained unchanged for over 23 years and has not been updated to reflect inflation, significantly eroding the fine value
• the penalty level is lower than that for other environmental and traffic offences (see Annex 1)
• the penalty level is not in keeping with wider developments within the UK and the European Union. For example:

1. Westminster City Council has set the fine level for engine idling offences at £80 (since 2017) to reflect the increased exposure risks associated with poor air quality hotspots and high levels of pedestrian activity
2. From September 2026, engine idling offences in Wales will be subject to fines ranging from £75 to £150 to ‘…reflect the serious consequence of air pollution which idling contributes to’[23].
3. Across Europe, penalties for engine idling offences are higher than in Scotland with fines of €49 in Luxembourg[24], €80 in Germany[25], €130 in Belgium[26] and €135 in France[27].

7.6
Having reviewed the evidence, ESS considers that Regulation 8(b) of the 2003 Regulations is ineffective environmental law. Whilst the issuing of FPNs has been viewed as a ‘last resort’, the evidence suggests that, in reality, the low value of the FPN acts as a barrier to enforcement as the costs of administering an FPN can be greater than the value of the penalty itself. In addition, the current level of the fine is disproportionately low compared to other offences and risks failing to provide a credible deterrent.

7.7
Given the above, ESS recommended to the Scottish Government that it should review Regulation 8(b) (which prescribes the current FPN fine level) and give consideration to the level at which the FPN would function as an effective deterrent for stationary idling offences. For the following reasons, the Scottish Government did not accept this recommendation:

• idling penalties in England also remain set at £20
• higher penalties for other offences (such as fly‑tipping) reflect different policy considerations
• any legislative change would require robust evidence and parliamentary resource
• idling activity is declining due to technological advances, including start/stop technology, increased uptake of electric vehicles, and cleaner bus fleets associated with LEZ implementation
• stationary idling contributes only a small proportion of overall air pollution

7.8
The Scottish Government further advised that its current focus is on education and public engagement rather than increasing penalty levels but indicated that the outcomes of the Welsh Government’s reforms will be considered in due course, once sufficient evidence is available, when assessing whether similar changes may be appropriate in Scotland.

7.9
ESS recognises the Scottish Government’s position, including its emphasis on proportionality, evidential requirements and wider policy considerations. However, as set out above, the effectiveness of enforcement depends in part on whether penalties operate as a credible deterrent. In relation to technological advances, while measures such as stop‑start systems, fleet electrification and cleaner vehicles are expected to reduce emissions over time, available evidence suggests that transition is uneven and varies across regions and socio-economic groups[28]. Additionally, between 2003 and 2024, there has been a 20% increase in petrol and diesel vehicles licensed in Scotland[29] (480,000 vehicles), with 90% of cars on the road in 2024 being petrol or diesel engined. On this basis, it is important that the deterrence principle inherent within the 2003 Regulations remains effective.

7.10
ESS considers that an enforcement system that is rarely used on the basis of the cost to administer it is structurally flawed and risks defeating the purpose of the statutory regime. Accordingly, ESS maintains its position that Regulation 8(b) should be reviewed with a view to increasing the level of the value of the FPN so that it no longer amounts to an operational barrier to local authorities, and acts as a credible and thus effective deterrent to drivers committing stationary idling offences.

[21] The effectiveness of enforcement measures – Litter and flytipping offences – enforcement review: final report – gov.scot

[22] Citizen Participation and Public Petitions Committee – PE1944 – Note by the Clerk

[23] Tackling stationary engine idling | GOV.WALES

[24] Grand-Ducal Regulation of 22 April 2009 amending the … – Legilux

[25] Keeping the engine running – Nature & Environmental Protection 2026

[26] Wallonia to fine drivers who keep car engine running | The Bulletin

[27] France Traffic Fines – Cosmos Legal

[28] Psychological interventions for environmental impact: A field experiment on reducing engine idling – ScienceDirect

[29] Transport Scotland – Transport statistics 2025 (road transport vehicles)

8.1
The adverse effects of poor air quality on human health are well established. These impacts may be particularly pronounced at a local level, where emissions from idling vehicles may create concentrated exposure in locations such as outside schools. Reducing avoidable emissions plays an important part in protecting public health and will be increasingly important should Scotland move towards more ambitious air quality standards.

8.2
In ESS’ view, the concerns raised within the representation are well made with the evidence demonstrating that:

• the statutory guidance lacked clarity and risked contributing to inconsistent application and, in some cases, incorrect interpretation of the law
• the absence of reliable and comparable data prevents meaningful assessment of how effectively the statutory regime is being applied across Scotland
• the FPN level set under the 2003 Regulations lacks credible deterrent value and is rarely used in practice because it is too low to justify the use of enforcement powers. In ESS’ view, this amounts to a failure to make effective environmental law

8.3
While ESS welcomes the steps taken by the Scottish Government to strengthen the statutory guidance, ESS accordingly recommends that Scottish Ministers take the following remedial measures:

• review and increase the level of the FPN to ensure it provides an effective deterrent
• introduce a mechanism that would allow for future adjustments to the penalty level, ensuring it maintains its deterrent value over time, including indexation in line with inflation
• finalise proposals for legislative amendment of the 2003 Regulations to implement the above changes within twelve months of the laying of this report in the Parliament, with parliamentary consideration taking place at the earliest possible opportunity

8.4
In accordance with Section 30 of the Continuity Act, Scottish Ministers must now prepare and lay an Improvement Plan before the Scottish Parliament setting out what they propose to do in response to this recommendation.