Caltrain's experiment with weekend express trains has proven to be a success, according to transit officials.

The weekend Baby Bullet train service started in January, Caltrain officials said. The pilot program was only supposed to last three months but the service has been extended due to its popularity.

The express service adds two round-trip express trains to the schedule. The trains travel between San Francisco and San Jose stations, stopping at Millbrae, San Mateo, Hillsdale, Redwood City, Palo Alto, Mountain View and Sunnyvale.

Express service cuts travel time between San Francisco and San Jose from one hour and 36 minutes to 57 minutes.

Caltrain officials said that ridership went up 30 percent on the bullet trains as well as on the local weekend trains.

"This is a strong indication that the new weekend Baby Bullet service is not just existing riders who changed to the Baby Bullet trains, but a real increase in overall ridership," Caltrain director of transportation Michelle Bouchard said in a statement.

Transit officials said that Caltrain's ridership overall has increased, with the average weekday ridership up 12.7 percent over last year and average weekend ridership up 21 percent from last year.