The GO system map shows seven train lines (or corridors), all departing from Toronto's Union Station and mostly named respectively after the outer terminus of train service. Although colours are assigned in a consistent fashion to each line in all official media, in colloquial parlance lines are only ever referred to by their names. Buses are numbered in blocks of 10, corresponding to the nearest train line, with the 40s and 50s reserved for express services along the 407 ETR corridor which does not have a corresponding train line.