Rail is an iron beam. Its main function is to provide a most economical, smooth and level surface for the smooth passage of heavily loaded vehicles at great speed. The two RAILS of the track also serve as a lateral guide for the running of the wheels.
It is of I section or Dumb-bell section. It is the original rail. The idea was that when the head of the rail was worn out during the period of service, the rail could be inverted and reversed without incurring any extra expenditure. Such RAILS have to be supported in chairs which rest on sleepers.
Later it was found that during the service the bottom table of the rail was dented by the long and continuous contact with the chair to such an extent that it was impossible to reuse it. Hence it was rejected and other types of rail were searched.
It is similar in shape to double headed rail with only difference that in bull headed rail more metal is added to the head to allow the greater wear and tear. The lower head or table was kept of just sufficient size to be able to withstand the stresses to be induced by moving loads. This rail also required chairs for fixing it to the sleepers. This proved the greatest drawback of this rail.
It is in inverted T-shaped rail. Having greater stability. It was developed by charles Vignoles as early as 1836.