Spanish Solution

The Spanish solution (also called Barcelona solution) has two railway platforms, one on each side of the line, to speed up boarding and alighting: passengers board from one side and alight to the other. If there are three platforms (one island platform and two side platforms) with two tracks, generally the center platform will be a shared exit platform, as there is no benefit in segregating arriving passengers. At most locations doors for exit open a few seconds before those for entry.

The principle was first used in 1895 at the (now closed) King William Street tube station in London, but came into wide use on (and takes its name from) the Barcelona Metro in the 1930s.

The solution was used in the United States in 1912 at Park Street Under on the MBTA's Red Line in Boston, and at Chambers Street on the New York City Subway in 1913, where the center platform is now closed.

On people movers at airports there are often dedicated platforms for boarding and alighting. This can have the additional advantage of preventing travellers heading in the wrong direction when alighting, and ensuring passenger segregation. The same principle is often used on ferries, monorails, and cable cars, fairground rides such as roller coasters, and in buildings such as theaters.

At a terminal station where trains are bi-directional (double ended) it is advantageous for the center platform to be for boarding and the side platforms to be for alighting. This permits an incoming train to enter on either track and remain in the station until it is ready to begin the next trip. Passengers boarding then do not have to know in advance which track the next train will depart from.