Summer heat and the defensibility of highway claims

Every winter highway authorities observe that, “bad weather causes potholes”. Despite some public cynicism, it is correct - water ingress, followed by repeated freezing and thawing, has long been regarded as the main, forgive the pun, driver of potholes. That makes the winter a busy time for Highway Inspectors.

The RAC has now added good weather to the causes of highway deterioration. It recently published research showing that, although potholes are usually linked with cold or wet winters, sustained hot and sunny weather also damages the network, because intense UV exposure and heat oxidise the bitumen binding the asphalt, leaving surfaces brittle and liable to crack. The warning follows a summer that has provisionally been declared the hottest on record, with five heatwaves and a peak temperature of 38.1C at Kew Gardens.

For highway authorities, this is not simply an engineering point. It has a direct bearing on the incidence of highway claims.

The statutory framework

Section 41 of the Highways Act 1980 imposes a duty on the highway authority to maintain the highway. Where a claimant establishes that a defect rendered the highway dangerous and caused their loss, there is a claim. However, the authority may rely on the statutory defence under s.58: that it took reasonable care to make sure that the part of the highway in question was not dangerous to traffic.

Two points should be kept firmly in mind. First, the burden lies on the claimant to identify the specific defect said to have caused the damage. An assertion that a road was generally in poor condition is not sufficient. Second, local authorities relying on a s.58 defence need to be sure it has two things in place: a regular cyclical inspection regime, with frequencies determined by risk, and a reactive system which responds promptly to defects reported by the public.

What counts as reasonable is informed by national guidance. Well-managed Highway Infrastructure: A Code of Practice endorses a risk-based approach, under which a heavily used distributor road may warrant monthly inspection and a lightly trafficked rural lane an annual one. Proximity to schools and shopping centres, residential density and traffic volumes all also factor into that assessment.

The RAC research adds a new factor to the public’s understanding of highway deterioration and we can expect to see claimants’ solicitors using it.

Why the RAC's findings matter

A risk-based regime is only as sound as the risk assessment underpinning it. If road surfaces are now under stress throughout the year, a maintenance programme premised on a quieter summer period will become more difficult to justify as reasonable.

Heat is not the only emerging pressure. Electric vehicles are materially heavier than their petrol and diesel equivalents. HGVs remain the principal cause of serious structural damage. New housing developments and large logistics sites can alter traffic patterns significantly and quickly. A lane which served a single farm may, within a short period, become the main access route for 200 new homes, carrying construction traffic well before those homes are occupied. In short, roads and their upkeep were – in a vast majority of cases – built and designed for uses that might now have shifted dramatically.

A policy that was set several years ago and has not been revisited will be vulnerable to challenge on those facts. Highway authorities should be able to demonstrate that their approach is dynamic: that it takes account of new evidence, including research of the kind the RAC has published, and adapts when the use of a road changes.

Practical steps

But what can a local authority actually do to better defend against pothole claims? There are three practical routes to consider.

The first is inspection capacity. Increased inspection will identify more defects and will therefore increase repair costs, and authorities should approach this with that consequence in view. It is, however, important to be clear about what the law requires. Defects can and do develop between inspections. A pothole which was not present at the last inspection does not of itself defeat a s.58 defence, provided the inspection frequency was reasonable.

The second is technology. A number of authorities have already deployed vehicles equipped with AI scanning to identify carriageway defects, and drone-based surveys are said to be in development. Such tools can extend coverage without a proportionate increase in resource, and they generate a detailed, time-stamped record of network condition which may prove valuable evidence.

The third, and frequently the decisive, factor is documentation. Policies should be grounded in research and reviewed at regular intervals. A highways manager giving evidence must be able to explain why each road is inspected at its particular frequency. The Court of Appeal in Wilkinson v City of York Council [2011] EWCA Civ 207 confirmed that limited resources will not of themselves justify an inspection regime which falls below a reasonable standard. The answer lies in a clear, evidence-based rationale recorded at the time decisions are taken.

Misconceived settlement strategies

It is important to be aware of the dangers caused by not taking a proper liability-based approach to these cases.

The most common claim is for damage to alloy wheels, typically valued at under £250. Some authorities have adopted a threshold approach. If the value of the case is below a certain level, claims are paid without investigation, on the basis that the cost of handling exceeds the value of the claim.

The rationale is understandable, but carries real danger. Many authorities will already receive thousands of wheel damage claims each year, and generative AI tools now enable any motorist to produce a persuasive letter of claim within minutes. A known practice of paying below a set figure is likely to encourage further claims, and volumes can only be expected to rise.

A better course for local authorities is to defend those claims which are defensible, including those of modest value. Where an authority has a sound inspection regime, has responded promptly to reports and can evidence both, it should say so and decline to pay. Plainly, that sends a clear message: an authority which is not at fault will not settle simply to dispose of a claim.

The pressure on the local road network shows no sign of easing. It is therefore critical that highway authorities treat their inspection and maintenance policies as living documents, keep them under review in light of emerging evidence, and record the reasoning behind them.

Henry Bermingham is a Partner at Weightmans.