Although some countries use very country-specific methods and apparatus, gritting around the world is carried out in largely the same fashion. Globally, the highest priority for gritting and snow removal tends to be urban routes, and most cities in countries that have regular snowfall maintain a fleet of gritting and snow clearing vehicles. Gritters are the first vehicles to be dispatched when snow hits, working the road for public safety and to keep the roads open.
Gritting is sufficient on its own in temperate countries as it can melt ice and make roads safe. In high snowfall countries, gritting prepares the surface for snow removal by melting the snow, giving snow ploughs more traction.
In those countries, once the snow stops falling, snow ploughs push snow away to the side of the road, but then gritters return for a second run to deal with remaining ice and snow. In the example below, a snow plough is working the streets of Moscow.
Responsibility for gritting
The individual homeowner is usually tasked with clearing paths and pavements in front of their home in suburban areas. In some countries this is punishable with a fine (ie USA), but in Europe the attitude is usually less punitive. Motorways and public roads tent to be different: councils and municipal bodies usually have the responsibility for these.
Snow removal after gritting
In urban centres where snow accumulates over the winter it is also further necessary to remove piles of snow after gritting the surface that build up on the side of the roads. There are a number of methods of doing this.
- Pulling snow is done when temperatures rise high enough for traffic to melt snow. The piles are broken up and spread over the road.
- Casting is the moving of snow by means of a shovel or plough to nearby public lands.
- Winging back is done on motorways, which means pushing snow banks further away from the road
The most expensive option, but necessary when there are no nearby places to dump the snow, is to remove it completely. This is usually done by snowblowers; vehicles that suck up piles of snow at the side of the road and load it into dump trucks, as illustrated below by a snow blower operating in the USA.
Gritting chemicals used around the world include:
- Sodium chloride - NaCl
- Calcium chloride - CaCl2
- Potassium chloride - KCl
- Magnesium chloride - MgCl2
- Ammonium nitrate - NH4NO3
- Ammonium sulfate - (NH4)2SO4
- Potassium acetate - CH3COOK
- Urea - (NH2)2CO
- Propylene glycol - C3H8O2
- Calcium magnesium acetate - C4H6O2Ca & C4H6O2Mg
- Sodium ferrocyanide - Na4Fe(CN)6•10H2O
- Methyl alpha-D-glucopyranoside - C7H14O6
In the European Union, 98% of chemical treatment material used in 2000 was salt: sodium chloride (NaCL). Salt suits the relatively mild European winter: effective down to −5 °C, at the most −7 °C. For colder temperatures, calcium chloride (CaCl2) is added to salt in some countries, but deployment is limited as it costs about 6 times as much as gritting salt. Gritting salt can either be pure marine salt or mined gritting salt. The latter is cheaper but the former is cleaner.
Other substances are used rarely and experimentally. Urea, alcohols, glycols are used at airports, beet juice has been used for pre-treatment and in Wisconsin, USA, surplus brine from cheese making has been used for this purpose. Other materials used as grit include:
- Wood ash