A money train is one or more railcars which have been remove from revenue service in a subway system for use in transporting fare collection from stations to the transit authority's headquarters, presumably to allow deposit of collected revenues into the bank. This train is typically used to carry money bags guarded by transit police to deter robberies. It is generally necessary because of difficulties in getting to and from stations using over street transport, and because, since the subway reaches every station, it makes sense to use the rail system itself to collect money from fare machines.