Steve Gooding, director of the RAC Foundation and former DfT director general, discusses the impact of April showers, subsoil issues and what could make a good inclusion in the Department for Transport's newly launched Structures Fund.

Looking to the skies as I write, I am reminded, as I am sure many Highways readers are, of the opening lines of Geoffrey Chaucer's Canterbury Tales:

Whan that Aprille with his shoures soote,

The droghte of March hath perced to the roote,

And bathed every veyne in swich licóur

Of which vertú engendred is the flour

…

Thanne longen folk to goon on pilgrimages 

Or, in other words, there's nothing quite like a much-welcome April shower to bring out the Spring flowers and turn people's minds to making a road trip. I'm not sure whether Geoffrey had much to say about road conditions.

According to the Met Office last winter ranks among the wettest on record (since the series began in 1836) for some parts of the UK: West Midlands, Cornwall and Leicestershire. Several other counties - including Dorset and Warwickshire, which recorded their second wettest winter - fell within their top ten wettest winters since 1836, and Southern England saw its fourth wettest winter – its wettest in over a decade.

Showers, yes. Sweet? Not so much.

Can you stand the rain?

I can think of three particular highway-related problems related to rainfall. There's a road safety issue – skidding, aquaplaning, spray and poor visibility, not helped by some poor driving behaviour. 

Second, the heavy downfalls that have become a new normal as the climate changes overwhelming drains and gullies and causing run-off – an environmental issue that has risen up the agenda. 

Third, which to my eye has had much less attention to date, is the impact the changing pattern and weight of rainfall could be having on ground conditions – the ground on which the highway sits. Or sinks.

We are all well aware of the pothole plague - even the transport secretary has been hit with a bill for pothole-related car tyre damage (as our press was eager to report). But what's behind, or more to the point, beneath this issue?

Beneath the surface

To some extent, it's clear that the surface defects we're experiencing are the product of past works needed to maintain the services that run beneath the carriageway. However good the standard of reinstatement, I have yet to be persuaded that the road is ever the same again until fully resurfaced. And what we have now reflects decades of carriageways being repeatedly broken and patched.

Then there's wear and tear – work we are pursuing at the Foundation will be shedding some light on this shortly. I recall being told that the axle-loading of trucks was the big issue, not the general level of traffic, but that may well not be the case particularly where there's been water ingress.

And then there's what's happening with the sub-soil. I'm no engineer but I've read about ‘shrink-swell' of clay and destabilisation of subsoil in the pages of Highways, and the evidence of my eyes on many of the roads I've seen, particularly in the East of England, is that sections of the carriageway have sunk such that one side of the road is markedly lower than the other. 

My worry is whether we'll find we've been focusing too much on the symptom – the prevalence of potholes - rather than the real structural problem.

My advice to my former colleagues in the Department for Transport is to earmark some of their Structures Fund for projects that could serve as pathfinders for testing different approaches for addressing the issues of ground movement and sub-surface stability and thus, hopefully, identify some innovative – affordable - solutions.

Steve Gooding is a regular contributor to Highways Magazine. For more from him, along with other great and informative content, click here to sign up and access the magazine - both online and in print.