Snow tires (winter tires) are tires designed for use in winter conditions, such as snow and ice. They are an alternative to the use of snow chains.
Snow tires are usually tires with a different rubber composition from all-weather tires. Cold-weather tires include a greater percentage of natural rubber and silica so there is not as much hardening as found in synthetic rubber in cold conditions: they provide better traction at lower temperatures. Snow tires provide more small-tread areas, increasing traction on snow and, in wet conditions, allowing water to escape from under the tire more easily. This reduces the risk of hydroplaning. In much of Scandinavia winter tyres have metal studs to improve grip on packed snow or ice, but such tires are banned in most other countries for the damage they cause to the road surface. Snow tires do not eliminate skidding on ice and snow, but they greatly reduce the risk.
In the United States and Canada, a "snowflake on a mountain" symbol means that the tire has exceeded the industry requirement for a reference (non-snow) tire.
In Europe, snow-tire requirements vary by country: in Austria, Estonia, Finland, and Sweden, the use of snow tires is a legal requirement during winter months (usually November to mid-April) or if snow or slush is present on road surfaces: failure to comply can result in on-the-spot fines from the police. Andorra, Italy, Norway and Switzerland all recommend snow tires but do not require them. Snow chains fitted to tires are required in Andorra, Austria, France, Germany, Italy, Norway and Switzerland in certain winter conditions.
Although there is no legal requirement to use winter tires, drivers in the United Kingdom are encouraged to use them by motoring organisations such as the AA, following the adverse winter weather conditions of 2010. Conversely, the same drivers were discouraged from using winter tires by car insurance companies who, owing to a failure to understand the safety benefits, reportedly charged higher premiums to drivers who fit winter tires. This has since been clarified as incorrect practice by the Association of British Insurers (ABI).
Snow chains, or tire chains, are devices fitted to the tires of vehicles to provide superior traction when driving through snow and ice.
Snow chains are attached to the drive wheels of a vehicle. Chains are usually sold in pairs and must be purchased to match a particular tire size (tire diameter and tread width). Driving with chains will reduce fuel efficiency and can limit the speed of the automobile to approximately 30 mph (50 km/h).
In snowy conditions, transportation authorities may require snow chains or other traction aids on vehicles. This could apply to all vehicles, or only those which do not have traction features, such as four-wheel drive or snow tires. Local requirements may be enforced at checkpoints or by other inspection. Snow chains should always be fitted to one or more drive axles of a vehicle, with varying requirements for dual-tire or multi-driven-axle vehicles that range from 'one pair of tires on a driven axle' to 'all tires on all driven axles' being required to have snow chains fitted whenever and wherever conditions and/or sign-age require it.
