The Caltrain Modernization Program will electrify the main line between San Francisco and the San Jose Tamien station, allowing transition from diesel-electric locomotive power to electric rolling stock. Proponents say electrification would improve service times via faster acceleration, allow better scheduling and reduce air pollution and noise. Electrification would also allow future expansion to downtown San Francisco. Electrified vehicles require less maintenance, but electrification will increase required track maintenance by about the same dollar amount, at least initially. The plan calls to electrify the system between San Francisco 4th and King Street station and San Jose Tamien station. Originally scheduled for completion by 2020, the schedule had slipped after three months of construction to December 30, 2021 and then April 22, 2022. At that point, Caltrain plans to use electric multiple units and increase service to six trains per hour in each direction.