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Road surface treatment: a stitch in time saves cash and carbon

It’s no coincidence that the increase in potholes in our roads coincides with a decrease in surface treatments, according to Paul Boss, chief executive of the Road Surface Treatment Association (RTSA).

Between 2012 and 2022, there was a 44% reduction in surface dressing applied to UK roads, while the cost and number of pothole repairs has risen.

Boss was speaking last week [18 March], alongside Lincolnshire County Council’s footways and surface treatments programme leader Andrew Creasey, at a seminar aimed to educate highway authorities on the benefits of the timely application of surface dressing.

Surface dressing involves the application of polymer modified emulsion and chippings to a road surface. If applied at the right point in a road’s life, before defects become visible, it will stop potholes forming at all, according to RTSA. For heavily trafficked roads, this is around 10 years after it was laid and for lightly trafficked roads 15 years.

Boss presented some calculations comparing lifetime costs of a carriageway in both pounds sterling and tonnes of carbon. He reckoned that for a heavily trafficked road over a 60-year lifespan, with surface dressing every 10 years, the cost per square metre would be £39 and the carbon emissions 9kg CO2 per square metre.  He compared this to renewing the surface course every ten years, and the binder course after 30 years which would lead to a lifetime cost of £116 per square metre and carbon emissions of 39 kg CO2 per square metre.

Creasey gave an honest insight into the juggling act that all local authorities face with a funding pot that won’t stretch to the maintenance and upkeep that their road networks require. He said that the authority had filled 18,000 potholes in the first two quarters of the financial year 2023/24 and – given recent weather conditions – expected that figure to rise significantly.

Lincolnshire’s approach is very much data based, said Creasey. Decisions on schemes for surface dressing, resurfacing or reconstruction are guided by data – as well as political pressures.

The amount of surface dressing applied by the council has fallen in the last couple of years, said Creasey. This was because the ‘green’ and ‘amber’ roads – those in better condition – had been treated first. ‘Red’ roads in poor condition require investment to get them up to scratch before surface dressing can be applied. For instance, a 15,000 sq m section of road earmarked for surface dressing in the next financial year will require a £300,000 investment first to patch it, said Creasey.

There were some reasons to be hopeful, though. Creasey showed a graph which mapped out the council’s total roads maintenance budget against a variety of states it has modelled: from managed decline to steady state to gradual improvement. Should the Department for Transport’s additional funding kick in as promised, the highways department could go from steady state of its roads to improvement. What had been labelled “the graph of doom” was hopefully now a “graph of optimism”, he said.

An interesting point Creasey made was the need to educate members of the public, many of whom have a negative perception of surface dressing. He said the council puts out information through its website, Facebook community groups and other social media to try and counter that misconception. Getting the sweeping regime right, when loose chippings are removed from a newly surface dressed road, is also really important for keeping road users on side, he added.


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