The improvements will bring the stations up to par with the Americans with Disabilities Act and also improve track capacity and safety.
At the main Palo Alto station on University Avenue existing pedestrian underpasses and ramps will be modified and the platforms will be replaced with longer ones.
The California Avenue station will have the center-boarding platform replaced with outside-boarding platforms on both sides of the tracks. A new underpass will be added and a fence between platforms will also be added to prevent passengers from crossing between tracks, according to Caltrain.
Both stations will remain in service during construction and work will be carried out during the weekends, according to Caltrain spokesman Jonah Weinberg.
Caltrain expects few delays due to construction and any disruption would be announced and planned in advance to minimize inconveniences.