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A winter service vehicle ( WSV), or snow removal vehicle, is a vehicle specially designed or adapted to Snow removal. Winter service vehicles are usually based on a dump truck chassis, with adaptations allowing them to carry specially designed snow removal equipment. Many authorities also use smaller vehicles on , Trail, and . Road maintenance agencies and contractors in temperate or polar climate areas often own several winter service vehicles, using them to keep the roads clear of road debris and safe for driving during winter. Airports use winter service vehicles to keep aircraft surfaces, , and free of snow and ice, which, besides endangering aircraft takeoff and landing, can interfere with the aerodynamics of the craft.
The earliest winter service vehicles were snow rollers, designed to maintain a smooth, even road surface for , although horse-drawn and gritting vehicles are recorded in use as early as 1862. The increase in motor car traffic and aviation in the early 20th century led to the development and popularisation of large motorised winter service vehicles.
However, with the increase in paved roads and the increasing size of cities, snow-paving fell out of favour, as the resultant slippery surfaces posed a danger to pedestrians and traffic. The earliest patents for snowplows date back to 1840, but there are no records of their actual use until 1862, when the city of Milwaukee began operating horse-drawn carts fitted with . The horse-drawn snowplow quickly spread to other cities, especially those in areas prone to heavy snowfall.
The first motorised snowplows were developed in 1913, based on truck and tractor bodies. These machines allowed the mechanisation of the snow clearing process, reducing the labor required for snow removal and increasing the speed and efficiency of the process. The expansion of the aviation industry also acted as a catalyst for the development of winter service vehicles during the early 20th century. Even a light dusting of snow or ice could cause an aeroplane to crash, so airports erected around airfields to prevent , and began to maintain fleets of vehicles to clear runways in heavy weather.
With the popularisation of the motor car, it was found that plowing alone was insufficient for removing all snow and ice from the roadway, leading to the development of Gritter, which used sodium chloride to accelerate the melting of the snow. Early attempts at gritting were resisted, as the salt used encouraged rusting, causing damage to the metal structures of bridges and the shoes of pedestrians. However, as the number of car crash increased, the protests subsided and by the end of the 1920s, many cities in the United States used salt and sand to clear the roads and increase road safety. As environmentalism increased through the 1960s and 1970s, gritting once again came under criticism due to its environmental impact, leading to the development of alternative de-icing chemicals and more efficient spreading systems.
Other common changes include the replacement of the factory stock tires with or mud and snow tires and the shortening of the vehicle's wheelbase to improve maneuverability. For smaller applications smaller trucks are used. In Canada, pickup trucks are used with snow removal operations with a blade mounted in front and optional de-icing equipment installed in the rear. Underbody scrapers are also used by some agencies and are mounted between axles, distributing plowing stresses on the chassis more evenly.
In most countries, winter service vehicles usually have amber light bars, which are activated to indicate that the vehicle is operating below the local speed limit or otherwise poses a danger to other traffic, either by straddling lanes or by spreading grit or de-icer. In some areas, such as the Canadian province of Ontario, winter service vehicles use the blue flashing lights associated with emergency service vehicles, rather than the amber or orange used elsewhere. In Michigan, green flashing lights are used. Many agencies also paint their vehicles in high-contrast orange or yellow to allow the vehicles to be seen more clearly in whiteout conditions.
Some winter service vehicles, especially those designed for use on footpaths or , are built on a far smaller chassis using small tractors or custom made vehicles. These vehicles are often multi-purpose, and can be fitted with other equipment such as brushes, lawnmowers or cranes—as these operations are generally unable to run during heavy snowfalls, there is generally little overlap between the different uses, reducing the size of the fleet required by the agency or contractor.
Modern winter service vehicles will usually also have a satellite navigation system connected to a weather forecast feed, allowing the driver to choose the best areas to treat and to avoid areas in which rain is likely, which can wash away the grit used—the most advanced can even adapt to changing conditions, ensuring optimal gritter and plow settings.Institution of Civil Engineers, pp. 53–54 Most run on wheels, often with or studded tires, but some are mounted on caterpillar tracks, with the tracks themselves adapted to throw the snow towards the side of the road. Off-road winter service vehicles mounted on caterpillar tracks are known as . Snowcats are commonly fitted with snowplows or Snow grooming, and are used by to smooth and maintain and snowmobile runs, although they can also be used as a replacement for .
Military winter service vehicles are heavily armoured to allow for their use in combat zones, especially in Arctic warfare and mountain warfare, and often based on or . Military winter service vehicles have been used by the United Nations, Kosovo Force, and the US Army in Central Europe during the Kosovo War, while during the Cold War, the Royal Marines and Royal Corps of Signals deployed a number of tracked vehicles in Norway to patrol the NATO border with the Soviet Union.
Winter service vehicle drivers usually work Part-time job, before and during inclement weather only, with drivers working a 12- to 16-hour shift. Main roads are typically gritted in advance, to reduce the disruption to the network. Salt barns are provided at regular intervals for drivers to collect more grit, and bedding is provided at road maintenance depots for drivers to use between shifts in heavy or prolonged storms.
Weather conditions typically vary greatly depending on altitude; hot countries can experience heavy snowfall in mountainous regions yet receive very little in low-lying areas, increasing the accident rate among drivers inexperienced in winter driving. In addition, road surface temperatures can fall rapidly at higher altitudes, precipitating rapid frost formation. As a result, gritting and plowing runs are often prioritised in favour of clearing these mountain roads, especially at the start and end of the snow season. The hazardous roads through mountain passes pose additional problems for the large winter service vehicles. The heavy metal frame and bulky grit makes hill climbing demanding for the vehicle, so vehicles have extremely high torque transmission systems to provide enough power to make the climb. Furthermore, because the tight found on mountain slopes are difficult for long vehicles to navigate, winter service vehicles for use in mountainous areas are shortened, usually from six wheels to four.
Aircraft 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.
In road snow and ice control, brine is often used as an anti-icer rather than a de-icer. A vehicle carries a tank of brine, which is sprayed on the road surface before or at the onset of the storm. This keeps snow and ice from adhering to the surface and makes mechanical removal by plows easier. Solid salt is also wetted with brine or other liquid deicer. This speeds de-icing action and helps keep it from bouncing off the pavement into the gutter or ditch.Cornell Local Roads Program, Snow and Ice Control Operations for Local Highway Officials 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.
Airport runways are also de-iced by sprayers fitted with long spraying arms. These arms are wide enough to cross the entire runway, and allow de-icing of the entire airstrip to take place in a single pass, reducing the length of time that the runway is unavailable.
Salt reduces the melting point of ice by freezing-point depression, causing it to melt at lower temperatures and run off to the edge of the road, while sand increases traction by increasing friction between car and roadways. The amount of salt dropped varies with the condition of the road; to prevent the formation of light ice, approximately is dropped, while thick snow can require up to of salt, independent of the volume of sand dropped.Institution of Civil Engineers, p. 27 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.
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 spread less dangerous potassium acetate or urea onto the runways instead, as these do not corrode the aircraft or the airside equipment.
Gritters can also be used in hot weather, when temperatures are high enough to melt the bitumen used in Asphalt concrete. The grit is dropped to provide a protective layer between the road surface and the tires of passing vehicles, which would otherwise damage the road surface by "plucking out" the bitumen-coated aggregate from the road surface.
The development of more advanced electronic systems in the 1980s allowed manufacturers to produce snow groomers which could work on and replicate a much wider range of terrains, with the most modern even able to produce and Mini ramp for snowboarding. Snow groomers are also used in conjunction with , to ensure that the snow produced is spread evenly across the resort. However, snow groomers have a detrimental effect on the environment within the resort. Regular pressure from the grooming vehicle increases the infiltration rate of the soil while decreasing the field capacity. This increases the rate at which water can soak through the soil, making it more prone to erosion.
Because 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 , with the largest being hauled by semi-trailer . In addition, the complicated melting process means that snow melting vehicles have a much lower capacity than the equivalent plow or blower vehicle; the largest snow melter can remove 500 metric tons of snow per hour, compared to the 5,000 metric tons per hour capacity of any large snow blower.
Snow melters are in some ways 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, because the snow is melted on board, the costs of transporting snow from the site are eliminated. On the other hand, snow melting can require large amounts of energy, which has its own costs and environmental impact.
In the event that specially designed winter service vehicles are not available for plowing, other service or construction vehicles can be used instead: among those used by various authorities are , , , pickup trucks and . can also be used to plow snow. Either a snowplow attachment can be mounted on the loader's arm in place of the bucket, or the bucket or snowbasket can be used to load snow into the rear compartment of a snowplow or dump truck, which then hauls it away. Snowplows are dangerous to overtaking; 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 can obscure the vision of other road users.
The most common chemical is rock salt, which can melt snow at high temperatures but has some unwanted side effects. If the salt concentration becomes high enough, it can be toxic to plant and animal life and greatly accelerate corrosion of metals, so operators should limit gritting to an absolute minimum. The dropped salt is eventually washed away and lost, so it may not be reused or collected after gritting runs. By contrast, the insoluble sand can be collected and recycled by Street sweeper and mixed with new salt crystals to be reused in later batches of grit.
Sea salt may not be used, as it is too fine and dissolves too quickly,British Standard 3247:1991, BSI Group. so all salt used in gritting comes from salt mines, a renewable source. As a result, some road maintenance agencies have networks of ice prediction stations, to prevent unnecessary gritting, which not only wastes salt but can also damage the environment and disrupt traffic.
The U.S. state of Oregon uses magnesium chloride, a relatively inexpensive chemical similar in snow-melting effects to sodium chloride, but less reactive, while New Zealand uses calcium magnesium acetate, which avoids the environmentally harmful chloride ion altogether. Urea is sometimes used to grit suspension bridges, as it does not corrode iron or steel at all, but urea is less effective than salt and can cost up to seven times more, weight-for-weight.Pearson, p. 436
In some areas of the world, including Berlin, Germany, dropping salt is prohibited altogether except on the highest-risk roads; plain sand without any melting agents is spread instead. While this may protect the environment, it is more labour-intensive, as more gritting runs are needed; because the sand is insoluble, it tends to accumulate at the sides of the road, making it more difficult for to pull in at bus stops. (1991). 9780419156703, Spon Press. ISBN 9780419156703
Grit is often mixed with hydrate sodium ferrocyanide as an anticaking agent which, while harmless in its natural form, can undergo photodissociation in strong sunlight to produce the extremely toxic chemical hydrogen cyanide. Although sunlight is generally not intense enough to cause this in polar and temperate regions, salt deposits must kept as far as possible from waterways to avert the possibility of cyanide-tainted Surface runoff entering fishery or farms.Pearson, p. 435
Gritting vehicles are also dangerous to overtaking; as grit is scattered across the entire roadway, loose pieces can damage the paintwork and windows of passing cars. Loose salt does not provide sufficient traction for motorcycles, which can lead to skidding, especially around corners.
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