On 20 September 1976, this premetro line was converted into a heavy metro line, which was later split into two distinct lines on 6 October 1982: former lines 1A and 1B, both serving Maelbeek. , the lines were reorganised and renumbered 1 and 5.
On 20 September 1976, this premetro line was transformed into a heavy metro line, which was subsequently divided into two distinct lines on 6 October 1982: former lines 1A and 1B, both serving Maelbeek. The lines were reorganized and renumbered 1 and 5.