Winter service vehicle

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A winter service vehicle (WSV), often known as a snow removal unit or snow removal vehicle due to its primary function, is a vehicle used to perform snow removal, the clearing of roads or other thoroughfares of ice or snow, which is difficult to cross and reduces the traction of motor vehicles. Winter service vehicles are usually based on dump trucks, with adaptations allowing them to carry specially designed snow removal equipment, although many authorities also keep a number of smaller vehicles for use on pavements, footpaths and cycleways. Many road maintenance agencies and contractors own multiple WSVs in order to keep the road network clear and safe for driving.^[1]

Winter service vehicles are also employed by airports, in order to keep runways and taxiways free of snow and ice, which if left untreated could cause accidents.^[2] In most countries, winter service vehicles usually have amber light bars, which are activated to indicate that the vehicle is working or moving at below the local speed limit.^[1] However, in some parts of Canada, blue flashing lights are used instead.^[3]

Contents 1 Types of WSVs 1.1 Gritter 1.2 Snowplough 1.3 Snow blower 1.4 Surface friction tester 1.5 Snow melting vehicle 1.6 De-icer 2 References 3 See also

[edit] Types of WSVs

[edit] Gritter

A gritter, also known as a salt spreader or salt truck,^[1] is the most common type of winter service vehicle. Gritters are used to spread grit, a mixture of sand and rock salt, onto roads. The grit is stored in the large hopper on the rear of the vehicle, and spread across the roadway by an impeller. Salt reduces the melting point of ice by a process called freezing-point depression, causing it to melt at lower temperatures and run off harmlessly to the edge of the road, while sand increases traction by increasing friction between car tires and roadways. The amount of salt dropped varies with the condition of the road; to prevent the formation of light ice, approximately 10 g/m² is dropped, while thick snow might require 40 g/m². Winter service vehicles can also be used in hot weather, when temperatures are high enough to melt the bitumen used in asphalt. Grit is dropped to provide a fine insulating layer between the road surface and the tires of passing vehicles, which can damage the road surface.^[4] The grit is sometimes mixed with molasses to help adhesion to the road surface. However, the sweet molasses often attracts livestock, who lick the road and can become addicted to the sugar.^[5] The grit is sometimes heated as it is passed out of the nozzle; this helps melt the ice and improves the solubility of the salt.

The salt dropped by gritters comes from a non-renewable source, and high concentrations of salt in soil kill plants. As a result, road maintenance agencies have advanced networks of ice prediction stations, to prevent unnecessary gritting which can damage the environment and disrupt traffic.^[6][7] Gritting vehicles are also dangerous to overtake; as grit is scattered across the entire roadway, damage can be incurred by passing cars, and the loose salt does not provide sufficient traction for motorbikes.^[1] Quieter rural roads may be considered too minor to grit, so grit bins are often provided for drivers and pedestrians to shovel onto the road themselves. In some areas of the world, including Berlin, dropping salt is prohibited altogether, except in on the highest risk roads. Instead plain sand, without any melting agents, is spread. Although this protects the environment, it is more labour-intensive, as more gritting runs are needed; and as the sand is insoluble, it tends to accumulate at the sides of the road, making it more difficult for buses to pull in at bus stops.^[8] Other areas, including Oregon, use chemicals similar in structure such as magnesium chloride, which are less harmful to the environment and cause less corrosion damage to metallic structures.^[9]

Gritters are among the winter service vehicles also used in airports, to keep runways free of ice. However, the salt normally used to clear roads can damage the airframe of aircraft and interferes with the sensitive navigation equipment. As a result, airport gritters spray less dangerous potassium acetate solution onto the runways instead.^[10]

[edit] Snowplough

Main article: snowplow

See also: Snowcat

Many winter service vehicles can be fitted with snowploughs, in order to clear roads which are blocked by deep snow. Many winter service vehicles include plough; 75% of the UK's Highways Agency vehicles can be fitted with a ploughing blade.^[11] In most cases, the ploughare mounted on hydraulically-actuated arms, allowing them to be raised, lowered, and angled to better move snow. In some areas of the United States and Canada, snowploughing is performed by graders. Front-end loaders can also be used to remove snow: they can use a snowplough attachment which mounts on the loader's arm in place of its bucket, or they can use their bucket or an attachment called a snowbasket to load snow into the rear compartment of a snowplow or dump truck which then hauls it away. Snowploughs are however dangerous to overtake; often, the oncoming lane may not be completely free of snow. In addition, the plow blade causes considerable spray of snow on both sides, which is a hazard to vision.^[1]

Most snowploughs run on wheels, often with snow chains, but some are mounted on caterpillar tracks, with the tracks adapted to throw the snow toward the side of the road.^[12] Off-road snowploughs mounted on caterpillar tracks are known as snowcats. Snowcats are used by ski resorts to for piste and snowmobile maintenance, and are also often used as a replacement for chairlifts.^[13] Snowcats have also been used by the Royal Marines for NATO in Norway during the Cold War.^[14]

[edit] Snow blower

Main article: snow blower

Sometimes known as rotating snowplows or snow cutters,^[15] snow blowers are used in place of snowploughs. Snow blowers typically clear much faster than ploughs, with some clearing in excess of 5000 tonnes of snow per hour,^[16] and can remove snow from the roadway completely, rather than piling it at the side of the road. ^[17]

[edit] Surface friction tester

Generally used at airports or major roadways before ice formation, the surface friction tester usually takes the form of a small car with a fifth wheel attached to the rear axle of the vehicle and canted slightly.^[18] Sensors calculate the friction between the wheel and the driving surface, and if friction falls below a safe threshold, alert the control centre to send out other winter surface vehicles to move the snow or ice from the runway, taxiways or apron.^[19]

[edit] Snow melting vehicle

See also: Metromelt

A snow melting vehicle works by scooping snow into a melting pit located in a large tank at the rear of the vehicle. Around the melting pit is a smaller tank full of boiling water, heated by a powerful burner. The gases from the burner are bubbled through the water, causing some of the water to spill over into the melting pit, melting the snow instantly. The meltwater is discharged into the storm drains.^[20]

As they have to carry the large water tank and fuel for the burner. snow melting machines tend to be much larger and heavier than most winter service vehicles, at around 18 meters (59.1 ft), with the largest being hauled by semi-trailer tractor units.^[21] In addition, the complicated melting process means that snow melting vehicles have a much lower capacity than the equivalent plough or blower vehicle; the largest snow melter can remove 500 tonnes of snow per hour, compared to the 5000 tonnes per hour capacity of the largest snow blower.^[16] However, snow melters are far more environmentally friendly than gritters, as they do not spray hazardous materials, and pollutants from the road surface can be separated from the meltwater and disposed of safely. In addition, as the snow is melted on board, the costs of removing the collected snow from the site is removed.^[22]

[edit] De-icer

See also: De-icing

Common at airports, de-icers spray heated de-icing fluid, often propylene glycol or ethylene glycol, onto icy surfaces such as the bodies of aircraft.^[10] These prevent ice from forming on the body of the aircraft while on the ground. Ice makes the surface of the wings rougher, reducing the amount of lift they provide. Ice also increases the weight of the aircraft and can affect the balance.

De-icing vehicles usually consist of a large tanker truck, containing the concentrated de-icing fluid, with a water feed to dilute the fluid according to the ambient temperature. The vehicle also normally has a cherry picker crane, allowing the operator to spray the entire aircraft in as little time as possible; an entire Boeing 737 can be treated in under 10 minutes by a single de-icing vehicle.^[10]

Some road contractors also chose to use de-icers as an alternative to gritters; the vehicle carries a tank of brine, which is sprayed on the road surface. Brine acts faster than solid salt and does not require compression by passing traffic to become effective. The brine is also more environmentally friendly, as less salt is required to treat the same length of road.^[23] At some airports, runways are de-iced by sprayers mounted with long spraying arms. These arms can cross the entire runways, and allow de-icing of the entire airstrip to take place in a single pass.^[24]

[edit] References

[edit] See also

• Cesspool emptier
• Emergency vehicle
• Engineering vehicle
• Gully emptier
• Street sweeper
• Waste collection vehicle