Electrification and San Francisco Downtown Extensions are not an either/or. These two projects are in fact complementary to each other. A fully electrified Caltrain serving Downtown San Francisco will produce the highest ridership and the best riding experience for Caltrain.
Without full electrification, Caltrain can still be extended to Downtown San Francisco using dual-mode locomotives, which will operate in electric mode underground and in diesel-mode above ground. However, dual-mode locomotives are not as reliable and have the same performance as diesel locomotives outside Downtown San Francisco.
Electrification without San Francisco Downtown Extension will still provide enormous benefits for all three Caltrain counties by reducing travel time, noise, and air pollution. Electrification also allows Caltrain to provide more frequent and faster service at smaller stations that are not served by Baby Bullet trains currently.