Top transport bodies and researchers have called for more work on comparing the benefits of pre-wet salt and brine road treatment solutions for winter service, after an initial study failed to provide conclusive results.
The study was carried out by the National Winter Service Research Group (NWSRG), working with the Transport Research Laboratory (TRL) and national partners including Transport Scotland and the former Highways Agency now Highways England.
Coordinated trials took place on three sites across the UK - A1, A9 and M27 - in the winter 2014/15 to compare the rate of loss of pre-wet and brine on roads in conditions close to freezing.
The sites incorporated road surfacings relevant to trunk road operators and local authorities and measured the rate of salt loss on the roads.
A full report released today by the NWSRG states: ‘It cannot currently be concluded that that there would be a significant difference between the percentage salt losses measured for brine and pre-wetted salt on UKPTS if equivalent amounts of salt were spread for each method.’
Findings did show that in the first two hours after spreading there is a higher rate of salt loss for pre-wet in direct comparison to the brine in UK specification Propriety Thin Surfacing (UKPTS) trials. Thereafter there was a similar loss for each type of treatment over the next few hours.
However it adds this direct comparison ‘is between a higher salt spread rate for the pre-wetted salt than the brine’.
It also found based on these comparisons: ‘Residual salt levels after brine spreading on hot rolled asphalt (HRA) would appear to exhibit greater longevity than salt levels after pre-wet spreading. It seems feasible similar behaviour would be seen on other dense surfaces such as denser types of SMA.’
The report states there is ‘potential for using brine-only treatments in certain circumstances’ but calls for more research to help create guidance on effective treatment methods for different conditions, as well as economic evaluations.