Research
The NWSRG, (National Winter Service Research Group) is a members group dedicated to advancing understanding of best practice for winter service delivery, taking the best from currently available knowledge and supplementing any gaps with new knowledge and research.
Following the recommendations set out in the independent report, commissioned by DfT, “The Resilience of England’s Transport Systems in Winter often referred to as the “Quarmby Report” , the NWSRG Steering Group is now a Technical Sub-Group of the UK Roads Board. In turn this is part of the UK Roads Liaison Group family of organisations. The NWSRG Steering Group comprises of members elected by the NWSRG membership and other invitees from the public sector representing national interests. Thus the NWSRG provides oversight and liaison for the development of guidance and new knowledge for the UK public roads sector.
- Foreword - Foreword and Using the Guide
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The NWSRG are pleased to present the latest version of the Practical Guide for Winter Service. This version of the guidance is the culmination of a process of detailed review to ensure that it continues to fit in with the requirements of the current national Code of Practice, ‘Well-managed Highway Infrastructure’.
The guidance endorses the risk-based approach advocated by the Code of Practice, which is a change from previous, more quantitative guidance and recommendations. This approach will provide authorities with increased flexibility to implement a winter service in full accordance with local needs, priorities and affordability. - Section 2 - Planning for Winter Service Delivery
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Good planning before the winter season commences is crucial to the success of the service. This includes ensuring that agreed and appropriate policies have been developed, service levels have been defined, an effective management and decision making system is in place, sufficient resources are available, and that all relevant staff are aware of, and familiar with, their roles and responsibilities. This section of the NWSRG Practical Guide will help authorities to review their current policies and practices, as well as providing references to further relevant information within other sections of the guidance.
- Section 3 - De-icer Types
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This chapter explains the principal de-icer types used on UK roads and footways. This chapter provides information on de-icer products typically used for treating UK paved assets to help prevent the formation of ice and for the treatment of snow and ice as well as to help provide a debonding layer to facilitate removal of snow and freezing rain.
- Section 4 - Salt Storage
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This section contains information on how salt should be stored and the options that are available to help maintain the salt in optimum condition. The most economical treatment rates are available when salt is maintained within the optimum moisture content range and the production of fine particles through handling is minimised. Proper storage is essential to maintaining this good condition however the condition of the salt should always be adequately monitored.
- Section 5 - Treatment Methods and Technologies
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This section provides guidance on the principal methods for the spreading of de-icing materials, applied by vehicles or other mechanical means.
- Section 6 - Spreader Management
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Calibration and testing is important to demonstrate that the correct amount of de-icer is being discharged by a spreader and that the de-icer that is being discharged is being correctly positioned on the highway. For this reason, it is important that every vehicle is individually calibrated and tested. In addition, it is also important that once a vehicle is calibrated; there is a continuous form of monitoring throughout the season to determine if a recalibration is required. It is expected that any vehicles manufactured to current standards should be capable of being calibrated in accordance with this document.
- Section 7 - Winter Service Decision Making
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This section of the NWSRG Practical Guide contains information and guidance relating to the winter service treatment decision making process.
In line with the approach advocated in the national Code of Practice ‘Well-Managed Highway Infrastructure’ the guidance contained within this section of the NWSRG Practical Guide is not prescriptive and is designed to assist authorities in taking a risk based approach to the decision making process they adopt for their networks.
As acknowledged by the Code of Practice, the quality of treatment decisions will be the key factor in determining both the effectiveness of the winter service and how it is perceived by users and the community. It is therefore an integral and crucially important factor in the delivery of an effective and successful service.
The content of this section of the NWSRG Practical Guide should be considered in conjunction with the information and guidance contained within other sections, notably those relating to Winter Service Planning, Treatment Methods, Spread Rates for Precautionary Salting, Treatments for Snow and Ice, and Treatments for Extreme Cold. These other sections provide important further information and guidance relating to a range of issues that impact upon the decision-making process, much of which should be considered before the winter season commences.
Winter service treatments are either ‘precautionary’ or ‘reactionary’ in nature. Precautionary treatments are carried out before, and to prevent, predicted winter weather hazards arising, whereas reactionary treatments are carried out to remove or ameliorate winter weather hazards that already exist. - Section 8 - Spreading Rates for Precautionary Salting
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This section of the NWSRG Practical Guide contains information regarding spread rates for precautionary salting operations undertaken in response to predictions of frost and ice formation in normal winter weather conditions on the UK road network.
- Section 9 - Treatments for Snow and Ice
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This section provides guidance on effective treatments for snow, ice and freezing rain based on the operational experience of practitioners and in combination with a review of the available research and literature.
- Section 10 - Treatments for Extreme Cold
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In this section we will consider extreme cold conditions when more generally available treatments are less effective.
The spreading of sodium chloride without suitable additives are considered to be less effective at or below -5oC at the time of spreading in low humidity conditions (below 100% relative humidity) and at or below -7oC in normal UK winter humidity conditions (at or above 100% relative humidity).
Based on research, the NWSRG consider that -15oC is the lowest practically effective temperature for salt as a de-icer on the road surface. Guidance is provided in this section for the use of alternative de-icers to (or with) salt in extreme cold conditions, including:
- Types of de-icer available
- Storage requirements
- Spreading equipment requirements
- Spread rates and treatment strategies
- Environmental and infrastructure considerations - Section 11 - Treatment of Footways and Cycleways
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The Footways & Cycleways Management Group (FCMG) pedestrian and cycle infrastructure definitions apply to this guidance and are shown below. These definitions are consistent with those presented in the Well-managed Highway Infrastructure Code of Practice and further information, including example photos and diagrams is available in the FCMG section of the UKRLG website.
- Section 12 - Weather Forecasting and RWIS
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Winter Service Decision Makers (WSDM) are faced with the challenge of determining the necessity, extent and timing of treatments, as well as the treatment rates to be applied, to mitigate the impact that winter conditions can have on the highway network. These decisions are based on the best judgement of the decision maker using the information available to them and within the overall context of the authority’s winter service policies and the content of their Winter Service Plan.
Weather forecasts are a key element of the information that WSDM should have available to assist with their decision-making process. Observation data from weather stations and sensors also form an important part of decision making and the monitoring process, allowing WSDM to see what is happening across their network and monitor the accuracy of forecasts.
This section of the NWSRG Practical Guide will help authorities to understand the suitability of different types of forecast for their local circumstances. It also provides practical guidance on issues including location and installation considerations for weather stations and sensors.
When considering a forecast it is important to remember that it is not a factual document but a prediction of the future state of the atmosphere and road surface. It will carry some degree of uncertainty which should be factored into the decision-making process.
This guidance will aid effective decision-making and support a risk-based approach to winter service decision making. - Section 13 - Route Selection and Optimisation
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Local circumstances, including authority risk appetites, financial and other resource constraints, vary widely across the country. Different parts of the UK are also subject to different statutory duties which will influence decisions taken. The guidance is designed to assist authorities to review and amend their winter service routes based on their local needs by adopting a risk and evidence based approach. This approach is recommended in Well-managed Highway Infrastructure Section B.7 Winter Service. In addition, it supports the case for authorities (excluding London) to apply for Department for Transport incentive element funding.
Using the principles outlined in this guidance, authorities should be able to justify winter service route network categorisation and demonstrate how individual treatment routes are selected, reviewed and amended using a consistent and transparent process.