A dispute has broken out between National Highways and the suppliers of a roadside barrier with a coating designed to tackle toxic air pollution that was trialled on the strategic road network (SRN).
The national roads operator told Highways that it will not be using the barrier on the SRN, while the company behind the product said that ‘predictable’ problems with the trial meant that few conclusions could be reliably ascertained.
The SmogStop barrier, designed and marketed by Envision SQ and Gramm Barrier Systems, is a combined noise and air pollution barrier, designed to use a photocatalytic coating to remediate nitrogen dioxide (NO2) from vehicles.
According to the report on the trial, published last month, the barrier was tested on the M1 near Tibshelf from September 2020 until August 2021, in a comparison with a similar wooden barrier.
A SmogStop barrier 100 metres long was installed nine metres from the carriageway, with a total barrier height 3.5 metres.
A 100-metre, three-metre high long wooden control barrier without the photocatalytic remediation was installed immediately south of and adjoining the SmogStop barrier.
The report notes that a SmogStop barrier was previously trialled at a height of six metres in Toronto, Canada.
It states that the research, carried out by independent experts on behalf of National Highways and GRAMM, found that the barrier had little impact on NO2 levels when compared to having no barrier.
Using the Government’s Emissions Factor Toolkit, the researchers estimated the photocatalytic remediation of the NO2 emissions to be equivalent to the removal of around 230 vehicles per day, from 100,000 vehicles travelling along the barrier.
In a statement, National Highways told Highways: ‘National Highways will not be pursuing this product for use on our network. National Highways does not endorse or recommend any products for use on roads that are not part of the Strategic Road Network. As the research is now complete, we will not comment further on this product.’
Envision SQ CEO Scott Shayko told Highways that despite problems in the trial, ‘some of which were predictable, and communicated to National Highways in advance’ the research recorded 'statistically significant reductions in NO2 at distances of five and 15 metres behind the barrier, compared to the control barrier'.
He cited issues such as the unreliability of diffusion tube technology used for measurements, lost data due to numerous instrument failures, and the distance from the carriageway and height of the barrier used.
He said: ‘Initially, we were pleased to be selected to work with National Highways in a co-operative manner to trial SmogStop Barrier.
‘Unfortunately, due to the limitations of some of the equipment deployed for testing by National Highways and equipment failure, the testing yielded limited results, from which few conclusions could be reliably ascertained.’
As Highways has reported, a number of links on the SRN have levels of nitrogen dioxide above legal limits with National Highways struggling to identify mitigation measures.
