Subway construction of steel support needs qualification
Qualification required.The subway is referred to as the "underground railroad", city rail transit system in narrow sense refers to operation of the underground.
But in general, because many such systems in order to cooperate with the construction of the environment, may also have existing ground sections, so usually covers the metropolitan area of all underground and on the ground of the high density transportation system.
From a professional point of view, the difference between light rail and subway, is not in heaven and earth, but in the heavy rail and the maximum cross section passenger flow: Rail weight per meter 60 kg per hour, 15 thousand passengers to 30 thousand passengers called light rail; rail weight per meter 60 kilograms, call the subway traffic per hour to 30 thousand 60 thousand passengers.
