HOT TOPICS - WINTER MAINTENANCE
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24 June 2009

Highways Term Maintenance Association renews call for strict approach on alcohol and drug misuse

22 June 2009, London, UK: The Highways Term Maintenance Association (HTMA) has renewed a call for a blanket ban on alcohol and drug misuse after welcoming action by one of its members to dismiss guilty employees, following random testing.

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9 June 2009

HTMA contribute to industry report on winter maintenance

9 June 2009, London, UK: The Highways Term Maintenance Association (HTMA) have contributed towards a report to parliament on the lessons for winter service by highlighting how they continued to deliver services and coped with the unprecedented demand on salt treatments, during the severe weather at the start of this year.

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Contents

Good Winter Maintenance is rarely noticed

Winter MaintenanceWinter maintenance teams will do their absolute best to keep the main routes through the UK clear this winter.

Spreading salt on the roads to make them safe is a vital task. The de-icing of roads in wintry conditions is a matter of concern for every family in the country, as well as every business. Good Winter Maintenance is rarely noticed: only when things go wrong does it become a public issue. When sudden bouts of cold weather bring traffic chaos, icy roads receive high-profile coverage in the media and local authorities are criticised, often unfairly, for not affording greater protection.Generally, the winter maintenance season lasts from October to April, during this period arrangements are made to ensure that highway authorities are able to respond to any weather conditions at any time, but preparations are started long before the winter is upon us, The vehicle fleet is maintained throughout the year to keep it in good condition. Drivers are trained and familiarised with their treatment routes. Decision-makers are trained by weather forecast providers to help them make the correct decisions. Duty rotas are drawn up to ensure 24 hour coverage. Simulation exercises are carried out across the country to emulate severe weather to ensure all the communication processes and decisions are tried and tested before the first frost of winter. The salt is ordered and stockpiled in the depots.

In order to provide an adequate winter maintenance service throughout the winter season highway authorities need resources including: Winter maintenance vehicle fleet fitted with snow ploughs; Loading facilities or vehicles; Snowblowers for extreme conditions; Sufficient drivers to provide the service for 24/7 cover; Increasing usage of Global Positioning Systems fitted on the vehicles; Data loggers to monitor salt usage; Decision making staff; Depots with salt stock management systems; System of weather stations on the network to monitor conditions. Every precaution is taken to make sure we are prepared for the unexpected, which of course can happen…

Facts and Stats

Did you know that in one winter season a typical HTMA member company:-

  • Operates as many as 200 gritters
  • Uses as much as 100,000 tonnes of salt
  • Has as many as 950 people involved
  • Covers as much as 10,000km of road network

What's up with the weather?

The weather we experience in the UK is unique – we have an atmosphere heavily influenced by the Gulf Stream, which keeps our weather warm and wet. During the winter our weather tends to be very marginal giving rise to nights where temperatures are just above or below freezing, making the decisions made by winter maintenance engineers very difficult. A frost forms when the moisture within the air condenses out by cooling. The temperature at which this takes place is known as the Dewpoint. If the surface on which the condensation is formed is or falls below freezing then a hoar frost will occur.

A mistake often made is assuming that if a frost has formed on grass verges and car windscreens, then a frost has formed on the road surface. During daylight hours road surfaces will be warmed by the sun, this heat is transferred down into the road creating a heat reservoir. During the night when the surface cools, the heat is conducted upwards and tends to warm the road surface.

In the British Isles the weather is changeable and that has an impact on daily life. The weather can change through extremes within the space of a day, hour or even minutes. This is where the British fascination with weather stems from. With research and advances in computing, however, weather forecasts are becoming more accurate. From thousands of bits of data collected by satellites, weather balloons and the global weather observing network, the Met Office's ‘supercomputer’ builds up a picture of the current state of the atmosphere. The Met Office run model simulations of the atmosphere, which is what all forecasts are based on.

Some people wonder if our hot summers are due to global warming. The scientific consensus is that humans are contributing to the greenhouse effect, leading to global warming.. One of the predictions over the coming decade is that snow will become less frequent in the British Isles; we are expecting milder winters, although the real threat of heavy snow and bitter temperatures remains.

And now for the winter weather forecast

Each year, the Met Office usually releases at least one severe weather warning for winter, predicting heavy snowfalls and bitter temperatures to come, although some areas of the UK, Scotland and the North of England for example, will have more than their fair share of severe weather warnings. In truth, the science of long-range forecasting is inexact, which is why the Met Office uses words such as probably, most likely or good chance. It is certainly better than tossing a coin, although if you were planning a country stroll in January or a picnic on the beach in March, it wouldn't be much help. But if you were a local authority wondering about grit and salt for roads, you'd be grateful for the warning.

On the forecast of snowfall highway authorities will instigate a number of measures. Some highway authorities may set up special “snow desks” to allow the co-ordination of resources when dealing with the event. Immediately prior to its arrival salt will be spread to ensure that the network is kept as free from snow as possible. The vehicle fleet will be fitted with snow ploughs and operatives will be placed on stand-by in their home depots. On snow arrival the fleet will be sent out to spread more salt and start to plough any snow accumulations on the network. This work will continue until the snow ceases and the network is clear. In extreme cases where snow has accumulated to considerable depths dedicated “Snowblowers” may be used. Work will continue until the network is completely cleared.

October 1987 hurricane

Long-range weather forecasters faced criticism for failing to predict the 1987 hurricane. The night before, BBC weatherman Michael Fish famously reassured viewers that the system would track along the English Channel but instead it cut a swath right across the south of the country. The storm ranks as the fourth most severe storm to hit Britain since records began. It cost a total of 18 lives, £1bn in repairs/clear-up costs and destroyed 15 million trees.

November 1999

Researchers predicted that winter 2000 would see a 20% above average number of "strong gale" and "whole gale" force winds. The research came from UK scientists Steven George and Dr Mark Saunders of University College London, who predicted that the south-east and east of England would see above average gales from December through to March, with Wales and the west of England also seeing above-average wind speeds. Their long-term gale forecast was the first to be approved by the UK Met Office and had proved accurate in predicting hurricanes in the US. In April 2000, gale force winds blew snow into drifts of up to 1.52m in depth.

The worst winters ever

1947 - the snowiest winter ever recorded, when blizzards raged for days and weeks on end, snowdrifts cut off large parts of the country and when the thaw finally came, it brought with it the worst floods ever recorded; 1963 - the coldest winter ever, when ice flows choked our rivers, the sea froze for 100 yards off shore, and millions of farm animals and wild creatures froze or starved to death; and, 1979 - 'The Winter of Discontent', when the savage snows and frosts were made worse by the strikes that paralysed Britain, causing power cuts, fuel shortages, transport snarl-ups, and left dustbins unemptied, hospitals unstaffed and bodies unburied for weeks on end.

Weather Forecasting and Decision Making

The Meteorological Office provides Highways Maintenance teams with weather forecasts which include road surface temperature information. The forecasts form part of a computerised Ice Prediction System, the system is monitored 24 hours a day throughout the winter and gives the Winter Maintenance Duty Officers the latest weather information as well as actual road surface temperatures and other information from various sensor sites around the UK. This information enables the Duty Officers to make their operational decisions. Precautionary salting is carried out when there is a clear probability of ice or snow, in that wet road surfaces are expected to fall to or below zero celcius The Ice Prediction System allows the Duty Officer to make a more accurate assessment of the need for salting - this results in a reduction of the risk of failing to salt when required but also provides a saving in costs since the number of unnecessary saltings is reduced. Decisions about what actions are required on the network for the forthcoming 24 hour period are made by suitably trained winter maintenance officers working for the highway authority. Training of these staff is provided by weather forecast providers. It provides officers with suitable background knowledge and information about the idiosyncrasies of our weather to enable the correct decisions to be made. In order to make a correct decision at the correct time officers need to be armed with a certain amount of information. Weather forecast providers provide a detailed road weather forecast on a daily basis this consists of: 24 hour text forecasts; Site specific graphical forecasts; Text forecasts for the next 2-5 days; Evening updates to the site specific graphical forecasts; Morning Summary of previous 24 hours’ weather; Telephone consultancy service; Thermal mapping of the network.

Officers are also able to obtain almost real-time data transmitted from the weather stations located at various locations adjacent to the road network. They provide detailed weather information relating to: Road Surface Temperature; Air temperature above the road surface; Dewpoint (Humidity of the air); Wind speed & direction; Road state (Dry, wet etc); Sensors in road that can detect the level of salt on the road. Once armed with this information winter maintenance officers will use their experience and knowledge of their network to make one of three basic decisions. Using a national standard decision-making matrix these are whether: To do a precautionary salt run; To defer the decision until further information is obtained; To take no action, but continue to monitor weather conditions.; In general every effort will be made to ensure that treatments are timed so that salt is spread on the network prior to the formation of ice. To ensure that salting has the maximum effect it is timed, wherever possible, to avoid the rush hour periods.

A night in the life of a winter maintenance controller

There is no such thing as a ‘typical’ winter maintenance night shift. During the winter season, circumstances change from night to night and from county to county and no two maintenance teams carry out the same tasks at the same time. But to give you some idea of what can happen during ‘a night in the life of a winter maintenance controller’ here are some real life scenarios:-

Winter Maintenance team is either diverted from its normal daily work or, if the gritting is needed at night, they are also on call round-the-clock from home. Over the summer we’ve been busy reassessing all our gritting routes so we can be even more efficient in how we deploy our machines. We have a fleet of gritting vehicles, the majority front line and a few spare. If the weather is really bad, all are called into service and, with several changes of driver, can work anything up to 24 hours without a break. Snow ploughs are able to be fitted to all vehicles when necessary. We can now grit all the A and B roads, and some important minor roads in about two and a half hours.

8pm Clock on at the depot and check the weather outside. Collect information about the night’s weather and decide about when and where to send out the gritting lorries, althought decisions are usually made well in advance of this. It sounds simple but with information coming in from several different sources there are some tough decisions to be made. If we decide not to grit will the roads be dangerous? If we send the lorries out unnecessarily money and resources will be wasted.

9pm First task of the evening is to check on reports from the Met Office weather centre. They are linked to our computer and send regular highways specific weather forecasts outlining air temperature, road surface temperature and potential weather heading our way .A computerised ice detection system is also used, so that when snow or ice is likely, the vehicles are able to swing immediately into action, carrying out precautionary gritting and snow clearing If the Met Office forecasts temperatures well below freezing. There’s no doubt about it – the roads need gritting tonight.

10pm Because we have invested in technology we can now make constant checks on the weather conditions from our control centre. We have weather stations throughout the county and sensors on strategic roads feeding vital information into our system. Tonight is our first really cold snap of the season – much later than usual. We frequently get called out to grit in October and even occasionally in September.

10.30pm All our lorries have satellite navigation systems on board. We have a computer record of where they grit and the amount of salt used along with speed and distance travelled. As we have to deal with insurance claims of damage allegedly caused by gritting lorries, this information is highly valuable.

11.00pm The Police call to ask for a specific stretch of minor road to be gritted. We check on the computer which gritter is closest and ask them to take a detour to the scene.

1.00am Information from the Met Office showed a possibility of rain in the early hours of the morning. We are watching the temperature and road sensor readings carefully as it could mean sending the gritting teams out again.

3.00am If it all stays quiet the lorries will shortly return to the depot and be washed down ready for action again. I give the Met Office a call to see if they have any further information on the potential rain. It looks like the rain has stayed further south so it should stay dry. Time, then, to make sure the paperwork is in good order for tomorrow’s shift.

5am Lock up and go home.

How can we get it wrong?

No matter how accurate the forecast, there are situations where we cannot salt the network prior to icy conditions. Such situations include:

  • When rain is followed by rapidly clearing skies, salting will normally start after the rain has stopped (to avoid the salt being washed away). Sometimes temperatures may fall by as much as 5°C per hour and the wet roads may well freeze before we have been able to salt them.
  • 'Dawn frost' occurs on dry roads, when early morning dew develops, falls on a cold road, and freezes on impact. It is impossible to forecast with any accuracy where and when this will occur.
  • Rush hour snowfall. When rain turns to snow coinciding with the rush hour, early salting cannot take place as it would be washed away and gritters cannot make progress due to traffic congestion.

Gritting: Which roads are treated?

Gritting is often not understood by the public. Firstly, it needs the action of traffic to work efficiently – otherwise it only clears the specific area where it falls. The car movement spreads it around the surface area. Secondly, if rain falls, it can wash away salt so the road needs to be treated again. If snow falls it’s the same.

Roads which are salted are usually dealt with in the following priority order : We may need to say that policies vary from County to County (although standard for HA) but generally work to similar principles/priorities (you will be able to come up with the words!).

Priority 1 Routes are all ‘A’ Class carriageways, and designated routes to A & E Hospitals. Then in order to maximize efficiency and scale of economy, other classes of carriageway which are required to be driven as part of the route, in linking up the ‘A’ Class network, will also receive this level of treatment. These will be as identified on the Winter Gritting Route Plans;

Priority 2 Routes are other major commuter roads (‘B’ class), major commuter/distributor roads carrying 4 service buses or more per hour between 06.00 and 10.00am, roads serving emergency services/public transport centres/comprehensive and secondary schools/higher education establishments, roads with gradients greater than 10% and carrying more than 1000v/day and main access roads to rural communities/villages. Third party funded Public Highways are also treated, however this will only continue for the duration of the external funding being made available. These will be as identified on the Winter Gritting Route Plans;

Other Carriageways it is NOT considered practical because of resources and costs to pre-treat all highways and Other Carriageways will not be pre-treated. The aim is that these will only be post-treated to remove ice or snow only after all the Priority 1 and 2 routes are treated and open to traffic and when snow or ice is likely to persist for a continuous period of 24 hours. This will also depend upon available resources.

Materials

Rock Salt

In order to prevent ice forming on roads there are a number of different treatments that can be used to treat the road surface prior to freezing conditions. Generally, the substance we spread on our roads is rock salt. This material, often mistakenly referred to as grit, is mined from underground mines. The mined salt, which, unrefined is a brown colour, is crushed and transported to salt stores managed by highway authorities throughout the United Kingdom. There are two sizes of granule spread on the UK network 6mm and 10mm.

Salt works by lowering the temperature at which water freezes. It is hydroscopic, which means that water is attracted to it as it dissolves and it relies on the action of vehicle tyres to be spread over the road surface. It will work at temperatures down to minus 10oC. At temperatures lower than this salt starts to become ineffective.

Pre-wetted Salt

This material can come in a number of different forms. Some highway authorities use pre-wetted salt to treat their network. It is effective to similar temperatures as described above. Advantages are that the salt usage can be reduced by about 25% It can be spread more evenly in the target areas. It can be applied at a faster application rate and the anti-icing effect is more immediate as it does not need to turn from a solid to liquid. However, the equipment needed to spread the material is expensive.

Agricultural By-products

A recent innovation has been the introduction of rock salt treated with agricultural by-products or molasses. This material, although slightly more expensive, is more widely being used. Manufacturers claim that 30% more material ends up on the road surface, rather than the adjacent verge, due to its adhesion properties,) thereby allowing highway authorities to reduce the spread rates. There is also evidence that it is less corrosive than pure rock salt and has less effect on bridges and street furniture.

Alternative Anti-icers

There are a number of other materials that are effective in preventing ice forming on carriageways these are: Urea & Konsin, Acetate and Ethylene Glycol. In general these materials are less widely used as they tend to be much more expensive than rock salt, are difficult to store and expensive plant is required to spread them.

Environmental Issues

The relationship between the UK road network and the environment is an important priority for the HTMA .As with all highway maintenance activities, there are environmental implications from winter road maintenance. Highways depots, spreading vehicles and the de-icing agent all contribute, but with good management(,) this impact can be minimised. The HTMA are committed to optimising winter maintenance practices in order to protect the environment. We know that the use of salt has an impact on the environment as it can damage plants and trees on the verge, cause water pollution and change the properties of soil. The Highways Agency has commissioned research into a more effective salting technique known as pre-wetted salt. This technique has environmental benefits because it uses about 25% less salt than during dry salting and there is less bouncing of salt to the roadside verge during spreading. The HTMA supports this research initiative and other environmentally beneficial techniques such as the correct storage of the salt / grit used for winter maintenance to avoid leaching and the calibration of spreaders to avoid over use of the salt. Rock salt when spread on the carriageway under normal winter maintenance activities is not considered to have an adverse effect on the environment. However, large concentrations in the form of water run-off from salt stockpiles can cause pollution of groundwater and adjacent watercourses unless correctly managed. Measures include storing salt on concrete hard-standing areas, installing drainage arrangements around these areas to prevent water entering the local drainage system, use of a modern well-maintained vehicle fleet and ensuring that decision-makers are properly trained to make correct judgements about the timing of their decisions so that salt is not wasted. All gritter vehicles ensure the correct salt spreading rates with some vehicles using computerised recording systems. We aim to ensure all salt is accurately spread at the minimum rates necessary to achieve safe conditions.The HTMA also supports the work of the National Salt Spreading Research Group (NSSRG), a group of Highway Authorities, Road Operators and Consultants that carry out pioneering research into de-icing materials to aid the removal of ice and snow from the trunk road network. The NSSRG strive to improve the winter maintenance provided on trunk roads by investigating the most efficient and effective methods of de-icing. For more information on the future research planned by this organisation please see the NSSRG publicity leaflet.

The Law

Highway Authorities have a duty under Section 41 (1A) of The Highways Act 1980 to ensure, “so far as is reasonably practicable, that safe passage along a highway is not endangered by snow or ice”. Highway Authorities achieve this by treating carriageways with an anti-icing agent. It is important to note that, apart from trunk roads and motorways, not all roads within the UK are treated to prevent ice formation. The cost and the effect on the environment would be too prohibitive. Routes that require treatment are determined traditionally by class of road and traffic usage, but, under the new legislation, highway authorities are required to undertake a risk assessment of the whole of their network. Once decided upon, treatment routes are designed to ensure that the treatment time does not exceed pre-agreed times.

Winter - respect the elements

The British winter is unpredictable. Bad weather can strike suddenly so the best advice when severe weather hits is to stay off the road. If you must drive, make sure you are prepared for the conditions. For advice about winter driving, click on the following link: www.thinkroadsafety.gov.uk/advice/winterdriving.htm

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