The Metro has three major lines extending throughout the city: A (green), B (yellow) and C (red). A fourth Metro line D is planned, which would connect the city centre to southern parts of the city (as of 2021, the completion is expected in 2028). The Prague Metro system served 589.2 million passengers in 2012, making it the fifth busiest metro system in Europe and the most-patronised in the world on a per capita basis. The first section of the Prague metro was put into operation in 1974. It was the stretch between stations Kačerov and Florenc on the current line C. The first part of Line A was opened in 1978 (Dejvická – Náměstí Míru), the first part of line B in 1985 (Anděl – Florenc).