The Welsh Government is trialling two new materials for low-noise highway surfaces, after disappointment with the longevity of previous materials.
It hopes the new materials will retain their integrity for at least 12 years. Reducing the harmful effects of noise pollution from roads is a key element of the Welsh Government’s draft 2018-23 action plan on noise.
Interventions over the last five years have included installation of noise barriers at key locations on the trunk road network.
The draft action plan explains that previous low-noise materials and processes have not achieved the desired design life, causing disruption during maintenance interventions and potentially worsening noise pollution as vehicles traverse roughened surfaces.
A Welsh Government spokesman told Highways that in some cases the actual life was shorter than the five-year warranty, but claiming against the warranty was difficult because the process could be clouded by factors such as ‘supervision recording, substrate condition and subjective assessment of condition’.
The news may concern some in Highways England where low noise surfacing is being used in key projects such as the A14 in order to support the environmental elements of the scheme, despite the potential to lower durability.
For the past 25 years, the Welsh Government has applied proprietary thin surface course systems (TSCSs) to its trunk roads.
‘These have varied greatly in quality, which is influenced primarily through installation and composition,’ he said. ‘In general TSCSs last between six and 11 years for Welsh strategic roads.’
Over the past year, the Government has been trialling a low noise stone mastic asphalts of its own specification. This is similar to materials used on German and Scottish roads but graded to incorporate the characteristics of Welsh aggregates.
It is made with a polymer modified binder and has been specified for three separate stone sizes.The Government expects this material to last for 16 years and more.
The material is undergoing a three-stage type approval test, starting with laboratory testing.The second stage saw the material installed at a quarry entrance. The third stage involves a location on the A55 Expressway.
The second low-noise material under trial is a cold applied ultra-thin surface course system (CAUTS), made with a smaller stone size (6mm) than regular systems and trialled with varying rates of binder application. This again uses a polymer modified binder.
The trial began in July on a 300-metre section of the A40 between Raglan and Abergavenny. The material’s adherence to concrete surfacing and its noise properties are being monitored. This material is expected to last for at least 12 years.
The Government is also studying possible treatment of concrete carriageways on the A55 at Ewloe, Flintshire, and the A483 at Wrexham.
The spokesman added: ‘The treatment utilises smaller stone sizes, which have been advantageous in TRL [Transport Research Laboratory] noise reduction tests, and a “lock in” treatment of fine binder spray to assist with retention of aggregate.’
