The Metro Improvement Project is Muni's program to retrofit the overhead wires in the subway system in order to reduce maintenance costs and to provide users with more reliable service. The first phase of the Metro Improvement Project, which was completed on January 29, 2007, involved replacing the wires between Embarcadero and Church stations. Phase 2 began immediately following Phase 1's completion will replace the wires between Castro and West Portal stations. Phase 2 of the project is expected to be finished in January 2008.

What this means for riders is that the K, L and M lines experience service interruptions. At 9 pm on weekdays (including Friday nights), these trains are replaced with a shuttle, but only between Castro, Forest Hill and West Portal stations.