It is common to think that the only difference between subways and trains is that the former run underground and the others on the surface. But… what about the subways that run on top of the earth? In fact, the differences between the two modes of transport are basically technological.
That of the trains is older: generally, the locomotive, which goes in front, pulls the other wagons along the tracks.
In some trains, there are two motorized cars, which guarantee more speed to the transport. Nothing, however, compared to the subway, where all cars are motorized, which allows for more efficient acceleration and braking rates.
Subways transport only passengers and circulate underground in urban centers. The cost of installing a subway line is usually much higher than that of a train. Mainly because tunneling underground is very expensive.
Generally, the money spent on works, tattoos and purchases of wagons powered by 600 volts of electricity is recovered in the long term with the sale of tickets.
On the other hand, freight trains, for example, have cheaper technology (locomotive engines can be powered by diesel oil and electricity), and thus it is less expensive to transport products.
That is why, if there is space on the surface to install a line, the natural choice is for the train. If the urban population density is high, it is best to put the wagons underground and use more advanced technology – in these cases, the preference is for the subway.
Trains and subways in Sao Paulo
In the capital of São Paulo, the compositions of Companhia Paulista de Trens Metropolitanos (CPTM) are powered by electricity, as are underground cars.
But don’t think that trains and subways in the metropolis are the same.
São Paulo trains are bigger than subway cars. They carry more passengers, but the wait between one train and another can be longer than the wait for the subway to arrive. The delay of trains also occurs because the distance between stations is greater than that of the subway.
In peripheral or less populated regions, trains are more common, because in these places it is (or was, at the time of construction) easier to install rails and erect stations without demolishing buildings or modifying avenues.
On average, on train lines, wagons travel more than two kilometers to reach the next station. On the subway, the distance between stations is greater than 500 meters and does not exceed 1.5 km.
Sources: Roberto Spinola Barbosa, professor at the Polytechnic School of USP, and press office at the São Paulo Metro (SP).