A half-track is a civilian or military vehicle with regular wheels at the front for steering and continuous tracks at the back to propel the vehicle and carry most of the load. The purpose of this combination is to produce a vehicle with the cross-country capabilities of a tank and the handling of a wheeled vehicle. Performance The main advantage of half-tracks over wheeled vehicles is that the tracks reduce the pressure on any given area of the ground by spreading the vehicle's weight over a larger area, which gives it greater mobility over soft terrain like mud and snow, while they do not require the complex steering mechanisms of fully tracked vehicles, relying instead on their front wheels to direct the vehicle, augmented in some cases by track braking controlled by the steering wheel. It is not difficult for someone who can drive a car to drive a half-track, which is a great advantage over fully tracked vehicles, which require specialized training. Half-tracks thus facilitate moving personnel and equipment successfully across varying terrain. The main disadvantage is the increased maintenance to maintain track tension, and the reduced life span of tracks (up to 10,000 km) compared to tires (up to 80,000 km). History Kégresse track The French engineer Adolphe Kégresse converted a number of cars from the personal car pool of Tsar Nicholas II of Russia to half-tracks in 1911. His system was named after him: the Kégresse track, which used a flexible belt rather than interlocking metal segments. He applied it to several vehicles in the imperial garage, including Rolls-Royce cars and Packard trucks. The Imperial Russian Army also fitted the system to a number of their Austin Armoured Cars. From 1916 onward, there was a Russian project by the Putilov Plant to produce military half-tracks (the Austin-Putilov model), along the same lines, using trucks and French track parts. After the Russian Revolution and the establishment of the Soviet Union, Kégresse returned to his native France, where the system was used on Citroën cars between 1921 and 1937 for off-road and military vehicles. Steam log hauler The concept originated with the hauling of logs in the northeastern US, with the Lombard Steam Log Hauler built by Alvin Lombard of Waterville, Maine, from 1899 to 1917. The vehicle resembled a railway steam locomotive, with sled steering (or wheels) in front and at the rear, crawlers driven by chains instead