Unlike Turku and London, the city of Brussels has kept its trams running continuously since 1869. However, the future of one particular line, number 55, has become uncertain.

Route 55 on the Brussels tramway is scheduled for replacement by a new metro line (M3) which will connect the north and south of the city. M3 is intended to complement four existing metro lines and create efficient transport links. With costs estimated at 2.3 billion euros, the construction of the M3 is arguably one of the biggest transport projects in Brussels.