The work is part of a larger program to enhance safety at railroad crossings in San Mateo County.

Work on a $2.8-million project to add additional signals to the Caltrain signal system will take place in Redwood City from Sept. 12-16 between 8 p.m. and 4 a.m., and in San Mateo Sept. 14-18 between 7:30 a.m. and 3:00 p.m.

A $2.1-million project to improve the radio communications system that operates the signals and switches on the railroad tracks is under way. The project will add a second radio channel, which will increase the system's capacity. Work will take place Sept. 8-10 between 5 a.m. and 4 p.m. at several locations near the Diridon and Tamien stations in San Jose.

On Sept. 16-17, crews will weld and grind the switches and replace worn asphalt, rails, ties and ballast on the tracks between the San Francisco and San Bruno stations. Sept. 14-17, crews will weld and grind the switches on the tracks between the Millbrae and San Mateo stations. Sept. 13-17, crews will replace worn asphalt, rails, ties and ballast on the tracks near the Sunnyvale station.