Your winter watch questions answered

Gritting roads and pavements

Who is responsible for gritting roads?

Highways authorities (county, unitary, metropolitan and London borough councils) are responsible for nine out of every 10 miles of road – about 225,000 miles throughout the UK. England and Wales has 174 highways authorities covering about 200,000 miles. They grit on average 40 per cent of their roads  80,000 miles.

What are the legal duties on clearing snow and ice from roads?

Under the Highways Act 1980 (England and Wales):

Section 41(1A) – "a highway authority is under a duty to ensure, so far as is reasonably practicable, that safe passage along a highway is not endangered by snow or ice."

Section 150 puts a responsibility on the highway authority to clear snow from the highway, but only if it is causing an obstruction.

A House of Lords ruling (Goodes v East Sussex County Council – 2000) concluded that a highway authority had an absolute duty to keep the fabric of the highway in a good state of repair so as to render it safe for ordinary traffic at all seasons of the year, but that did not include a duty to remove the formation or accumulation of ice and snow on the road.

The Traffic Management Act 2004 (England) requires authorities to do all that is reasonably practicable to manage the network effectively to keep traffic moving. In meeting the duty, authorities should establish contingency plans for dealing promptly and effectively with unplanned events, such as unforeseen weather conditions, as far as is reasonably practicable.

UK Roads Liaison Group – 'Well-maintained Highways: Code of Practice for Highways Maintenance and Management (2009)'

Given the scale of financial and other resources involved in delivering the Winter Service it is not reasonable either to – provide the service on all parts of the network; ensure running surfaces are kept free of ice or snow at all times, even on the treated parts of the network.

Why don't councils grit all roads?

Councils in the UK are responsible for about 225,000 miles of road. It would cost hundreds of millions of extra pounds to grit all roads. Also, many roads are simply too narrow or too steep for gritting lorry to navigate. Instead, councils try to find other solutions like supplying local grit bins for residents, liaising with parish councils and community groups to grit more residential or remote areas and working with farmers to clear rural areas.

Are councils responsible for gritting pavements?

Technically, most pavements are considered highways and so fall under he remit of councils. Decision on which surfaces to treat are based on factors such as how frequently and by how many people they are used, if there are alternative routes that could be used by pedestrians and whether there is a more practical way of clearing them such as community schemes.

Can people be sued if someone falls on a path or pavement they have cleared?

There is no law against people clearing pavements or public spaces. Ministers have repeatedly welcomed "public-spiritedness" and said "common sense" and "benefit of the doubt" should always prevail when considering litigation. A court would have to deem someone as having been "wholly incompetent or irresponsible" for another to successfully sue them for injury.

The Department for Transport published a Snow Code to clarify any confusion

What information to do councils use when deciding to grit?
As well as being updated with regular national forecasts and local information for nearby weather stations, Winter Duty Managers monitor a network of sensors embedded in roads across the UK. Each is connected by cable or mobile phone technology to an automatic weather station (grey box by the roadside) and measures road and air temperatures, rain, dew and salt levels. The sensors are sited either on a representative stretch of road (no nearby trees, buildings or bridges, which offer some protection from the cold), or traditional cold spots. The weather stations then beam back information to an intranet for officials to monitor, along with analysis by meteorologists using local weather forecasts.

Grit supplies

How much grit did councils order ahead of this winter?

Councils ordered about 1.3 million tonnes of salt ahead of this winter gritting season (Oct 1 to March 1). This is almost double the 700,000 tonnes used through all of last winter, and 100,000 more than was used during the severe winter of 2010/11.

We don't know if 1.3 million is more than councils have ever had, but it's the most in recent years since detailed national figures started being collated.

How much grit are councils expected to have for each winter?

The 2010 Quarmby Review on Winter Resilience recommend English highways authorities set a 'winter resilience benchmark' for councils of 12 days/48 runs-worth of salt ahead of each gritting season (October 1 to late March 1). The Department for Transport says these recommendations should be adopted.

How much do they use throughout winter?

It all depends on how much snow and ice we have, and how long it lasts.

Last winter was relatively mild and about 700,000 tonnes was used. The severe and early cold during November 2010 saw councils use about 300,000 tonnes, and during the course of that winter 1.2 million tonnes was used.

The Department for Transport carries out regular audits of local authorities to monitor salt levels.

What contingency plans are in place should a council run out?

Many councils have set up arrangements with neighbouring authorities to share supplies if stocks get low and gritting equipment if weather is particularly severe in some areas and not others.

The Department for Transport has a strategic stockpile for use as a last resort. This year it's about 305,000 tonnes, with a further 120,000 being held by the Highways Agency. Salt from the national stockpile, spread between depots throughout the UK, is released on a weekly basis to the councils which the Department for Transport considers are the most in need.


How much do councils spend on gritting over the winter?

It will vary dramatically from region to region and between years, depending on the weather, but the 2010 Quarmby Review estimated the total winter maintenance budget for councils across England to be about £160 million a year.

How much does grit cost?

Prices are in the order of £30 – £40 per tonne in normal market conditions. The cost can vary depending on how far it is being transported and the time of year it is ordered. Some councils will also join together to buy in bulk, thus getting at discount price.

What contingency plans are in place should a council run out?

Many councils have set up arrangements with neighbouring authorities to share supplies if stocks get low and gritting equipment if weather is particularly severe in some areas and not others.

The Department for Transport has a strategic stockpile for use as a last resort. This year it's about 305,000 tonnes, with a further 120,000 being held by the Highways Agency. Salt from the national stockpile, spread between depots throughout the UK, is released on a weekly basis to the councils which the Department considers are the most in need.

Impact on council services

When and why do councils close schools?

Routes to large schools are gritting priorities for councils as they know how important keeping them open is both in terms of continuity of teaching for pupils and avoiding costly and disruptive childcare for parents. It's either the headteacher or the local council which makes the decision to close a school. It is not a decision taken lightly and advice from the emergency services will be considered, as will the weather forecast. Reasons to close a school include dangerous road conditions nearby, a shortage of teachers who can safely make it in or problems with vital supplies such as heating or water. Schools appreciate it can be a huge inconvenience to parents but the safety of pupils and teachers are the primary concern.

When and why are bin collections cancelled?

Last year virtually all councils were able to continue rubbish collections as normal and of the few that couldn't, arrangements were made to collect at the earliest opportunity. However, the public's safety always comes first. Sending a 26 tonne dustcart down an icy residential street packed with cars and pedestrians is extremely dangerous. Where collections are missed they will be made up at the earliest possible opportunity, for example, at weekends. In some areas, collections of regular household waste will be prioritised over the collection of recycling, which does not rot. When outside temperatures are below zero, there is no risk to public health by rubbish being left out for a short while longer than normal.

Technical questions

What is road grit?

The most common material used to treat road surfaces prior to freezing is rock salt. Rock salt is mined from underground mines. It can also be combined with grit which helps to provide traction and grind up the salt. Rock salt is a brown colour because it is unrefined and contains impurities, so it is often referred to as grit.

How does gritting the road work?

Grit works by lowering the temperature at which water freezes. It relies on the action of vehicle tyres to be spread over the road, so requires traffic to be effective.

Where does road grit come from?

Most of the salt is mined in Cheshire. The main supplier is Salt Union, which can produce 6,000 tonnes per day. Cleveland Potash, in Middlesbrough, produces salt as a by-product of its main operations and usually produces about 3,200 tonnes per day. This year about one in 10 councils have arranged contracts with salt suppliers abroad, but this approach would not be a practical solution for all councils.

Does grit keep?
Yes, if it is kept under cover and not exposed to rain. This is why councils keep their salt under a waterproof sheet or in barns. In these conditions stockpiles will keep for a couple of years at least and probably much longer, but we never find out because councils have normally used and replaced stocks in that time. If a pile is left out in the open it will still keep for months, depending on the amount of rain, but gradually become soggy to the point where the gritter can't spread it evenly. The pure salt will also dissolve leaving a higher percentage of the orange-brown impurities making it less effective at thawing ice.

How does gritting work?
Rock salt lowers the freezing point of moisture on the road surface, stopping ice from forming and causing existing ice or snow to melt. For grit to work most effectively it needs traffic to crush and spread it across the road. When it snows heavily at night, though a road is gritted the snow will often still settle. Unfortunately that means for the first few drivers it may be slippery.

Why do councils grit the same stretch of road repeatedly?
This normally happens during prolonged snowfall when the sludge, caused by previous gritting and traffic flow, starts to wash older grit away and so risks the road surface freezing. Rain will also wash away salt. Ahead of a sub-zero night, gritting ideally needs to take place after rain but before freezing as grit spread on ice needs to then be worked into it by moving traffic to make it thaw. The often very small window of opportunity may be missed, or a surprise downpour may take place after a road's been treated so councils will re-run an area if needed. Councils sometimes have to contend with 'freezing rain' – supercooled rain which falls when the surface temperature is below zero, freezing on impact – which means they may need to re-grit areas.

Can it get too cold for grit to work?

Yes. Salt will work at temperatures down to minus 8-10 degrees C. Below that temperature salted roads will still freeze.

Don't councils put stone grit on the roads as well as rock salt?

Stone grit is only usually used on hardpacked snow and ice. In conditions where snow has already settled, grit can be mixed with salt to provide traction and help break up frozen surfaces.

What is pre-wetted salt?

Pre-wetted salt is salt that is mixed with water. It can come in a number of different forms and works at similar temperatures to rock salt. The advantages to pre-wetted salt are that it can be spread more evenly and more quickly, cutting salt usage by up to 25 per cent, and it gets to work faster as it doesn't have to dissolve first. But the equipment needed to spread the material is more expensive.

Can you use any other sorts of salt to grit the roads?

Pad white salt – a waste product of table salt – can also be used as a de-icer, but it is more expensive and needs to be used in combination with rock salt and grit.

Some highways authorities also combine molasses, an agricultural by-product, with rock salt. This material is more expensive, but improves adhesion so that more of the salt mixture ends up on the road surface rather than spraying onto verges.


20 November 2015

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