Rethink on use of liquid brine to prevent ice on roads

Winter roads

If trials this winter prove liquid brine is effective at preventing ice forming on roads, this approach is likely to be more widespread for UK winter service says Justin Ward.   

Liquid brine spreading as a treatment method to prevent ice forming on roads, think of a big tank of salty water and a number of spray nozzles, is not currently widely used for winter service in the UK.  However, a number of countries across Europe and North America are starting to use it as their preferred treatment option and the practice in the UK could be set to change.

The research from Germany found that liquid brine, as compared against pre-wet salt, took effect more quickly and actually stayed on the road surface for a longer period of time. 

Commencing early next year trials by the Highways Agency, Transport Scotland and Lincolnshire County Council will be exploring the use of liquid brine on their networks.  If successful, this method of precautionary winter treatment might become more commonplace both on the strategic and local road networks in the UK.

A study was undertaken in 2011 by TRL on behalf of the Highways Agency that led to the decision not to use liquid brine as the research failed to recover a sufficient level of residual salt on the road. The technique is used to a limited extent on the strategic road network but the case was not made for it to be the preferred default approach.  However, this conclusion is being questioned in light of the findings from a study from Germany that was presented at the International Winter Road Congress, held in February this year. 

Since then, the UK members of the World Road Association Winter Service Technical Committee (TC), have been gaining further insight and evidence on how liquid brine is actually effective as a winter service treatment.  This has led to the decision to appoint TRL to undertake the research on behalf of the National Winter Service Research Group (NWSRG) - a sub group of the UK Roads Board that sits under the UK Roads Liaison Group (UKRLG).

The research from Germany found that liquid brine, as compared against pre-wet salt, took effect more quickly and actually stayed on the road surface for a longer period of time.  Additionally as liquid brine is sprayed onto the road surface it is apparently less likely to be dispersed as pre-wet salt.  Balanced against this is the additional weight of liquid that has to be transported by the spreading vehicle.  Pre-wet is the most common winter treatment method in the UK, although dry salt and dry salt with an agricultural by-product added to it are also used. 

Stewart Leggett, strategic impacts manager at Transport Scotland said:  “Experience from overseas is suggesting that through brine only pre-treatments more salt is staying on the road and for longer, therefore giving a more resilient and safer winter service. In Scotland we have made significant advances in our winter service since 2010 and we see real potential for this brine treatment technique”.

Martin Hobbs, the Highways Agency’s head of asset resilience and a member of the TC said:  "Brine treatments could provide benefits across our network and specifically with the further roll out of smart motorways will allow more flexible operation in challenging conditions as the technique acts faster than pre-wetted salt”.  

Brine treatment may make it possible to spread closer to the optimum treatment time and therefore avoid peak traffic flows; there is also a resilience argument as liquid brine could be more responsive to changing circumstances.  The Environment Agency would also welcome any reduction in the amount of sodium chloride used and finding its way into water courses and groundwater. 

The trials will facilitate a direct comparison between pre-wetted salt and liquid brine on the same night, with the same atmospheric conditions, traffic levels and road surface.  The aim will be to fully understand the level of residual salt on the road surface and hence the effectiveness of the precautionary winter service treatment method.

Even if the trials are successful it is unlikely that there would be a significant change in the next couple of years or so.  There would need to be a strong case for investment in new spreading equipment and implementation is likely to be influenced by timings for highway maintenance contracts.  When changing to pre-wetted salt the Highways Agency invested some £45m and so any shift to liquid brine spreading, even partially, would need to be fully justified and budgeted.   


Justin Ward is Senior Policy Officer at the Chartered Institution of Highways & Transportation (CIHT).  CIHT provide the Secretariat support to the World Road Association (UK).  The concept of Resilient Networks, was the theme of the World Road Association UK Technical Seminar, Dinner Debate and Congress, that took place on the 4/5 November in Belfast.  To see more about the event, along with the presentations, please visit