Snow chains

Snow chains, or tire chains, are devices fitted to the tires of vehicles to provide increased traction when driving through snow and ice. Snow chains attach to the drive wheels of a vehicle or special systems deploy chains which swing under the tires automatically. Although named after steel chain, snow chains may be made of other materials and in a variety of patterns and strengths. Chains are usually sold in pairs and often must be purchased to match a particular tire size (tire diameter and tread width), although some designs can be adjusted to fit various sizes of tire. Driving with chains reduces fuel efficiency, and can reduce the allowable speed of the automobile to approximately , but increase traction and braking on snowy or icy surfaces. Some regions require chains to be used under some weather conditions, but other areas prohibit the use of chains, as they can deteriorate road surfaces. Snow chains were invented in 1904 by Harry D. Weed in Canastota, New York. Weed received for his "Grip-Tread for Pneumatic Tires" on August 23, 1904. Weed's great-grandson, James Weed, said that Harry got the idea of creating chains for tires when he saw drivers wrap rope, or even vines, around their tires to increase traction on muddy or snowy roads. At this time, most people in rural Northern regions wouldn't bother driving automobiles in the winter at all, since roads were usually rolled for use with horse-drawn sleighs, rather than plowed. Automobiles were generally not winter vehicles, for a variety of reasons until the 1930s or 1940s in some areas. Only in urban areas was it possible to remove snow from streets. He sought to make a traction device that was more durable and would work with snow as well as mud. In July 1935, the Canadian Auguste Trudeau obtained a patent for his tread and anti-skidding chain. In snowy conditions, transportation authorities may require that snow chains or other traction aids be installed on vehicles, or at least supplied for them.