The use of coloured asphalt in road tunnels has helped to cut lighting costs without compromising driver safety. Are coloured roads a step towards achieving the holy grail of carbon and operational savings?
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Highways carbon management and the need to cut costs have brought the issue of lighting our roads to the fore.
A recent Highways Agency proposal to turn off the lights on a stretch of the M5 from midnight until 5am was met with a mixed response from road safety groups.
Meanwhile, a report by local authority body CSS has stated that the installation of remote monitoring systems, to control the brightness of lamps when roads are lightly-trafficked, could save local authorities up to £35M annually.
An alternative option
Now, the US government has started to talk about another option. According to Nobel prize-winning physicist Steven Chu, appointed by President Obama as energy secretary, a global initiative to produce light-coloured roofs, roads and pavements so that they reflect more sunlight and heat, could potentially deliver carbon emission savings equivalent to taking all the world’s cars off the roads for 11 years.
What does this mean for UK highways? Tarmac national special products manager James Freeman does not believe such changes signify the end for conventional asphalt.
Instead he thinks that on many stretches of road, as well as in specific locations such as tunnels and junction approaches, the reflective qualities of light-coloured asphalt surfacing have the potential to deliver even better driver visibility and could cut lighting costs.
“Light-coloured asphalt is as durable as the traditional black stuff. Adding quartzite aggregate, light-coloured pigments and high-quality polymers with binders ensures it is suitable for all highways applications.”
James Freeman, Tarmac
Freeman says: “There is a strong body of evidence gathered in mainland Europe which demonstrates that light-coloured asphalt pavements have managed to reduce lighting and deliver significant financial savings without compromising driver visibility or safety.
“While this doesn’t mean we can reach for the dimmer switch across the entire road network, light-coloured asphalt used in specific locations, in conjunction with a wider package of measures such as remote monitoring systems, could reduce energy and lighting bills.
“Light-coloured asphalt is also as durable as the traditional black stuff. Adding quartzite aggregate, light-coloured pigments and high-quality polymers with binders to enhance the mechanical stability of the asphalt mix ensures it is suitable for all highways applications,” says Freeman.
According to reports from surfacing manufacturer Colas Geneve, light asphalt surfaces in tunnels can deliver lighting savings of between 30% and 40%.
Opportunity in the UK
In the UK, the full potential for light-coloured asphalt has still to be realised.
Typically, it has been used to demarcate areas such as bus and cycle lanes. But the material’s luminance properties and durability, when a polymer modified binder is added, offer wider opportunities for surfacing.
Applicable areas include those where one would normally expect street lighting including many road stretches, tunnels, intersections and roundabouts.
Tarmac has developed Mastertint to provide local authorities with a high-quality, light-coloured asphalt. It provides all the qualities of conventional asphalt with pigment to ensure that the colour is retained.
Light-coloured asphalt is not the sole answer to cutting costs and carbon across local authority roads. However, it could be beneficial when used as part of a wider package of measures in specific locations to reduce costs, drive down carbon emissions, increase visibility and improve road safety.
In the Confignon Tunnel, near Geneva, Switzerland, field trials showed that one spotlight out of two could be turned off because of the increased luminance, or brightness, of the surfacing. In this project, savings made on lighting have meant that additional capital costs for resurfacing were recouped within four years.
Positive data about visibility and luminance performance of coloured pavements has also been sourced from the International Commission of Illumination.
A three-month study conducted by this organisation across several pavement types reveals that light-coloured asphalt delivers the highest specular reflection factor and luminance coefficient of any material.
Highways special: Lighting the way