Ash Dieback Management: Highways Act Section 154 Duties

Ash dieback disease has emerged as one of the most significant threats to UK woodlands and roadside trees in recent decades. With an estimated 80% of ash trees expected to succumb to this devastating fungal disease, landowners adjacent to highways face increasingly complex legal responsibilities under Section 154 of the Highways Act 1980. Understanding these duties is crucial for property owners, as failing to manage diseased ash trees appropriately can result in substantial legal liabilities, enforcement notices, and potential prosecution. This comprehensive guide explores the intersection of ash dieback management and highway safety obligations, providing essential information for UK landowners navigating this challenging landscape.

Understanding Ash Dieback and Its Impact on UK Trees

Ash dieback, caused by the fungus Hymenoscyphus fraxineus, first appeared in the UK in 2012 and has since spread rapidly across the country. The disease affects both young and mature ash trees, causing leaf loss, crown dieback, and ultimately tree death in most cases.

Key symptoms of ash dieback include:

• Diamond-shaped lesions on bark
• Wilting and blackening of leaves
• Progressive crown dieback
• Epicormic growth (shoots from the trunk)
• Increased susceptibility to secondary infections

The Forestry Commission estimates that the UK hosts approximately 150 million ash trees, with the disease now present in every county from Cornwall to the Scottish Highlands. Areas particularly affected include Kent, Norfolk, Suffolk, and parts of Wales, where the disease first established itself. The economic impact is staggering, with removal and replacement costs potentially reaching £15 billion nationwide.

For landowners with ash trees near highways, the progression of this disease creates an urgent need for proactive management, as infected trees become increasingly brittle and prone to sudden limb failure or complete collapse.

Section 154 of the Highways Act 1980: Legal Framework

Section 154 of the Highways Act 1980 grants highway authorities specific powers to address vegetation that poses risks to road users. This legislation is particularly relevant in the context of ash dieback, as diseased trees represent a significant hazard to highway safety.

Under Section 154, highway authorities can require landowners to:

• Remove dead, diseased, or damaged trees overhanging the highway
• Cut back branches obstructing visibility or traffic signs
• Fell trees that present an immediate danger to road users
• Maintain vegetation to prevent obstruction of street lighting

The legislation applies to all trees within falling distance of the highway, not just those directly overhanging the road. This means that large ash trees up to 30 metres from the carriageway may fall within scope, depending on their height and condition.

Highway authorities, including local councils and Highways England for major roads, can serve notice requiring works within 14 days. In cases of imminent danger, authorities may undertake emergency works without notice and recover costs from the landowner. Failure to comply with a Section 154 notice constitutes a criminal offence, potentially resulting in fines and prosecution.

Landowner Responsibilities for Ash Trees Near Highways

Property owners bear primary responsibility for trees on their land, regardless of who planted them or when they became diseased. This duty of care extends to ensuring trees do not pose risks to highway users, neighbouring properties, or the general public.

Essential landowner obligations include:

• Regular inspection of ash trees for disease symptoms
• Commissioning professional arboricultural assessments
• Maintaining appropriate public liability insurance
• Documenting all inspections and management actions
• Responding promptly to highway authority notices

The frequency of inspections should reflect the tree’s condition and proximity to the highway. Trees showing advanced ash dieback symptoms near busy roads may require monthly monitoring, whilst those in early disease stages might need quarterly assessments. Professional tree surgeons typically charge £150-£350 for detailed condition assessments, depending on the number and accessibility of trees.

Landowners in high-risk areas such as the Chilterns, Peak District, and Yorkshire Dales, where mature ash populations line many rural roads, face particular challenges. The cost of managing multiple diseased trees can be substantial, with removal of a single large ash tree near a highway potentially costing £800-£2,500, depending on size and location.

Risk Assessment and Tree Safety Inspections

Implementing a robust risk assessment programme is essential for demonstrating reasonable care and potentially defending against liability claims. Professional arboriculturists use various assessment methods to evaluate ash trees affected by dieback.

Common assessment approaches include:

• Visual Tree Assessment (VTA): Basic inspection identifying obvious defects, typically costing £75-£150 per hour
• QTRA (Quantified Tree Risk Assessment): Statistical approach calculating failure probability, usually £200-£400 per assessment
• THREATS (Tree Hazard: Risk Evaluation and Treatment System): Comprehensive evaluation considering multiple factors, approximately £300-£500

Key risk factors specific to ash dieback include basal lesions, which significantly compromise structural integrity, and the presence of honey fungus or other secondary pathogens. Trees retaining less than 50% live crown are generally considered high risk and may require immediate action.

Documentation is crucial for legal protection. Maintain detailed records including inspection dates, findings, photographs, remedial actions taken, and rationale for management decisions. This evidence proves invaluable if authorities challenge your management approach or accidents occur.

Management Options and Best Practices

Managing ash dieback near highways requires balancing safety, ecological considerations, and financial constraints. Not all infected trees require immediate removal; management strategies should reflect individual tree conditions and site-specific factors.

Retention and Monitoring

Trees showing minor symptoms in low-risk locations may be retained with increased monitoring. This approach suits trees with:

• Less than 25% crown dieback
• No basal lesions
• Good overall vitality
• Sufficient setback from highways

Pruning and Crown Reduction

Selective pruning can extend safe retention periods whilst maintaining some ecological value. Professional pruning typically costs £200-£600 per tree and may include:

• Removing diseased branches
• Reducing crown weight
• Creating wildlife habitat through monolith retention

Complete Removal

Trees presenting unacceptable risks require felling. Factors necessitating removal include:

• Advanced crown dieback exceeding 50%
• Significant basal damage
• Proximity to high-traffic routes
• Evidence of root plate movement

Removal costs vary considerably based on location, with roadside trees requiring traffic management adding £500-£1,500 to standard felling charges. Work on A-roads and motorways requires specialist contractors with appropriate certifications, potentially doubling costs.

Working with Highway Authorities and Compliance

Establishing positive relationships with highway authorities facilitates effective ash dieback management. Most councils employ tree officers who can provide guidance on local policies and expectations.

When engaging with authorities:

• Request written confirmation of verbal discussions
• Seek pre-application advice before major works
• Provide comprehensive management plans
• Demonstrate proactive risk management

If served with a Section 154 notice, respond immediately. Authorities generally show flexibility when landowners demonstrate genuine engagement and present reasonable timescales for completing necessary works. Negotiating phased approaches for multiple trees can help manage costs, potentially spreading expenses over several financial years.

Some local authorities, including Derbyshire County Council and Devon County Council, have published specific ash dieback guidance for landowners. These resources outline local procedures and may identify grant funding opportunities.

Financial Implications and Available Support

The financial burden of managing ash dieback can be substantial, particularly for landowners with extensive roadside boundaries. Total costs for surveying, felling, and replanting a single mature ash tree typically range from £1,500-£3,500.

Potential funding sources include:

• Countryside Stewardship Grants: Up to £1,200 per hectare for woodland management
• Tree Health Restoration Grant: Covers felling costs for diseased trees
• Local Authority Grants: Variable schemes offering 50-75% cost contribution
• Insurance Claims: Some policies cover diseased tree removal

The Woodland Trust and Forestry Commission provide additional support through advisory services and subsidised replacement trees. The England Woodland Creation Offer provides up to £10,200 per hectare for establishing new woodlands, potentially offsetting ash removal costs.

Tax relief may be available for woodland management expenses, with professional fees and safety works potentially qualifying as allowable deductions. Consulting an accountant familiar with forestry taxation is advisable for substantial projects.

Future Planning and Replanting Strategies

Whilst managing immediate ash dieback risks is essential, planning for long-term landscape recovery is equally important. Replanting with diverse, resilient species helps maintain highway screening, ecological value, and landscape character.

Recommended replacement species include:

• Native alternatives: Oak, field maple, wild cherry, small-leaved lime
• Disease-resistant selections: Some ash cultivars show tolerance
• Climate-adapted choices: Species suited to projected future conditions

Consider establishing replacement trees before removing diseased ash where possible, ensuring continuous canopy cover and minimising landscape impact. This approach particularly suits rural highways where mature ash trees contribute significantly to local character.

The UK Government’s England Tree Action Plan aims to treble tree planting rates by 2024, with specific provisions for replacing trees lost to disease. Engaging with local tree strategies ensures replanting efforts align with broader landscape objectives.

Conclusion

Managing ash dieback whilst fulfilling Highways Act Section 154 duties presents significant challenges for UK landowners. The intersection of tree disease, legal obligations, and highway safety demands careful navigation, substantial resources, and proactive engagement with authorities. By implementing robust inspection regimes, maintaining comprehensive documentation, and adopting risk-based management approaches, landowners can fulfil their legal duties whilst managing costs effectively. As ash dieback continues spreading across the UK, collaboration between landowners, highway authorities, and arboricultural professionals becomes increasingly vital for maintaining safe highways whilst preserving our treasured landscape heritage. Early action, though potentially costly, ultimately proves more economical than reactive management following enforcement notices or, worse, accidents resulting from fallen trees. The coming decade will test our collective ability to manage this unprecedented tree health crisis whilst maintaining the safety and character of our highway networks.