General

Rail transport is an energy-efficient [3] and capital-intensive means of mechanised land transport and is a component of logistics. Along with various engineered components, rails constitute a large part of the permanent way. They provide smooth and hard surfaces on which the wheels of the train can roll with a minimum of friction. As an example, a typical modern wagon can hold up to 113 tonnes of freight on two four-wheel bogies or trucks. The contact area between each wheel and the rail is tiny, a strip no more than a few millimetres wide, which minimizes friction. The track distributes the weight of the train evenly, allowing significantly greater loads per axle and wheel than in road transport, leading to less wear and tear on the permanent way. This can save energy compared with other forms of transportation, such as road transport, which depends on the friction between rubber tires and the road. Trains have a small frontal area in relation to the load they are carrying, which reduces air resistance and thus energy usage, although this does not reduce the effects of side winds.