The winter viability plan

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A 24/7 service in severe weather conditions

AgentsOver 250 Council agents are mobilised from the end of November to the beginning of March to ensure the winter road service - weather surveillance, patrols in the field by officers from ten sectors in the department, with feedback and broadcasting of information, equipment maintenance, gritting in the event of black ice or snow and salt stock management.

In liaison with Météo France, the road service keeps a constant eye on weather conditions. As soon as forecasts indicate a potential risk for the roads, the ten operational managers, responsible for a sector in Orne, are put on alert. Depending on the conditioins observed locally during their patrol, they decide on what action to takeWhen traffic conditions worsen, special road information is provided at 8:30 am each morning (6:30 if circumstances require) to the prefecture, the regional road information and coordination centre in Rennes and the local media, including France Bleu Basse-Normandie and Normandie FM.

In winter, roads are treated in order of priority

  • Priority n°1: Main structural network – 450km – 27/7 action.
  • Priority n°2: Main non-structural network – 530km – action 24/7 after P1.
  • Priority n°3: Secondary access network, – 1,960km – action during the day, after P2.
  • Priority n°4: Other secondary network – 2,860km – action to ensure safety (not systematic) during the day, after P3.

New measures for school transport

Experimented in three school sectors this year (Gacé, Le Theil and Rémalard): In the event of black ice or snow this winter, school transport will be ensured on adapted circuits, using gritted, cleared roads with priority P1, P2, or P3. The aim is to prevent interruptions to school transport as far as possible or to reinstate services as quickly as possible on pre-established circuits, linking town or village centre bus stops.

The goal is to transport three-quarters of all pupils, by ensuring 40% of the regular circuits. Information will be provided to schools and families upstream and via e-mail, internet, SMS and the press.

The principles of service

Preventive treatment

Salting roads to prevent or delay the formation of ice, only of the main highways (P1 level).

Curative treatment

  • For ice Salting
    the roads using specific doses of salt or salt mush - on level P2, P3 and occasionally P1 when preventive measures have not been taken,
  • For snow
    Use of a snow plough to remove as much snow as possible, the remaining layer will be salted to help remove it as traffic flows.

There isn’t really any preventive treatment for snow! The salt spread on the roads can only delay the point at which snow starts to settle. To melt of layer of 5cm of snow when temperatures are at -5°C, you would need 350g of slat per m², i.e. 20 times the current dose.

Salt stocks: 7,000 stored by Orne Council

Stocks de sel The quantities of salt spread during winter depend on how severe weather conditions are: They can vary from 2,500 tons in a mild winter to over 10,000 tons during a very severe winter.

To meet these requirements, Orne Council has salt stocks located around the department, making a total of 7,000 tons available at the start of winter. This stock is regularly replenished but can go down rapidly during a severe weather period, when up to 600 tons a day can be spread.

Some useful info on the use of salt

Grains of salt

This form is effective up to -6°C and should mainly be used for curative treatment. On a dry road, it is soon projected on to the verges by passing traffic.

Brine

Salt is disolved in water to form brine, which is effective beyond -6°C, but its action is limited in time because as the ice melts, the salt concentration falls. Brine is particulary well suited to preventive use on dry roads.

Pre-wetted salt

A mixture of the two previous forms, pre-wetted salt offers the benefits of both forms, but none of the drawbacks: Stays on the road, and is fast and durable.

Stay alert! Road conditions and adherence do not return to normal immediately after the salt spreader has been!

Use of sand

Sanding is different from salting and is the use of abrasives which do not make the snow or ice melt, but which only help to « nail » it to the surface to improve adherence. This method is used when deicing substances are ineffective or not available…

Salt and the environment

During each operation, 90-180kg of salt per kilometre is spread, depending on the dosage. For the full duration of the winter period, this means – depending on how harsh the winter is – one to twelve tons per kilometre on a (P1) level road.

While the impact on fauna and the water tables are negligeable, run-off water does see an increase in chlore (CI-) ion content, and the penetration of salt into the ground can reduce ites permeability.

This is why road agents ensure that the the right dose of salt is always used.

The winter service equipment

Generally called « gritters », the winter service vehicles are trucks fitted with an automatic spreader and a snow plough. Orne Council’s services have 33 vehicles, 22 of which are mobilised 24/7. They are used to clear snow on the main road network.

Key figures

  • 250 agents mobilised
  • Period: from 28th November 2011 to 27th Febraury 2012
  • 35 winter service vehicles
  • 7,000 tons of salt in stock

The cost of the winter service

Engins d'entretienThe cost of keeping the roads viable throughout the winter varies depending on how harsh conditions are. From €0.7 million during a mild winter, it can reach €1.7 million during a severe weather, as in 2009-2010 for example.

These figures include the deicing products, the depreciation of the winter service vehicles, and the remuneration of stand-by and overtime of agents.

Driving in winter: Hints and tips

As the start of winter

Check and prepare your vehicle, fitting « winter » tyres where appropriate.

Before leaving

Check the weather forecast and road conditions, and take the relevant measures (chains, warm clothing, water, warm non-alchoholic drinks, food in case you are immobilised).