There are plans for new rail bridges, new stations, and rehabilitation of the rail line to serve a commuter rail service to connect Union City, Fremont, and Newark to San Francisco and San Jose.
The proposed Dumbarton Rail Corridor service would provide six westbound trains originating from a rebuilt Union City intermodal station; after crossing the rebuilt Dumbarton Cut-off bridges, three trains would proceed north to San Francisco and three trains would proceed south to San Jose, making limited stop service at the existing Caltrain stations.
From Union City, trains would stop at stations in Fremont (Fremont Centerville Station), Newark and Menlo Park/East Palo Alto before joining the main Caltrain line at Redwood City (northbound) or Menlo Park (southbound).
In the afternoon, the six trains would return from San Francisco and San Jose to Union City.
No reverse commute, mid-day, or night-time trains would be part of the initial service.
Two more stations could be added in Redwood City (2nd Avenue) and Hayward (Hayward BART) if rider participation would justify the cost.

SamTrans purchased the entire Dumbarton Cut-off from Redwood Junction to Newark Junction for US$6,900,000 (equivalent to $11,900,000 in 2019) in early 1994, with the help of a loan from Caltrans.
Although the Dumbarton Rail Corridor was almost fully funded in 2001 (the Metropolitan Transportation Commission estimated the total capital cost for the Dumbarton Rail Corridor was US$129,000,000 (equivalent to $186,300,000 in 2019); of that, 91% had been secured or was pending via local sales taxes in San Mateo, Alameda, and Santa Clara Counties), subsequent studies, including the 2003 Dumbarton Rail Corridor Project Study Report, identified several deficiencies in the existing infrastructure.
The 2003 Project Study Report proposed replacing the Dumbarton Rail Bridge swing span with a new bascule span, with the option for remote control from the Caltrain operations center or local control; the report also proposed replacing the Newark Slough Bridge swing span with a simpler steel girder swing span under local control, normally left closed to prioritize rail traffic over marine traffic.
Other proposed improvements included a proposed fourteen-span bridge over Alameda Creek to separate freight and passenger traffic.

The required improvements to infrastructure drove up project costs dramatically.
In 2004, the total capital cost had increased to an estimated US$277,600,000 (equivalent to $375,800,000 in 2019).
However, Regional Measure 2 (RM2) was approved by a majority of Bay Area voters in March 2004, raising toll rates by US$1 on the region's toll bridges.
US$135,000,000 (equivalent to $182,700,000 in 2019) was allotted to the Dumbarton Rail Corridor project from the increased tolls as one of the headline projects cited by supporters of RM2.
In 2008, US$91,000,000 (equivalent to $108,100,000 in 2019) in RM2 funds were loaned from Dumbarton Rail Corridor to BART for work on the Warm Springs Extension.
The 2008 estimate for DRC capital costs had risen to US$596,000,000 (equivalent to $707,700,000 in 2019), compared to the nearly US$300,000,000 (equivalent to $406,100,000 in 2019) in available funding that had been committed with the passage of RM2 in 2004, reducing the feasibility of Dumbarton Rail Corridor.
The $91 million loan would become a grant in 2014 when the Metropolitan Transportation Commission voted to forgive the terms of the loan.
With RM2 funds deprogrammed from Dumbarton Rail Corridor, the project was suspended.
Efforts continue to revive the project.
There are plans for new rail bridges, new stations, and rehabilitation of the rail line to serve a commuter rail service to connect Union City, Fremont, and Newark to San Francisco and San Jose. The proposed Dumbarton Rail Corridor service would provide six westbound trains originating from a rebuilt Union City intermodal station; after crossing the rebuilt Dumbarton Cut-off bridges, three trains would proceed north to San Francisco and three trains would proceed south to San Jose, making limited stop service at the existing Caltrain stations. From Union City, trains would stop at stations in Fremont (Fremont Centerville Station), Newark and Menlo Park/East Palo Alto before joining the main Caltrain line at Redwood City (northbound) or Menlo Park (southbound). In the afternoon, the six trains would return from San Francisco and San Jose to Union City. No reverse commute, mid-day, or night-time trains would be part of the initial service. Two more stations could be added in Redwood City (2nd Avenue) and Hayward (Hayward BART) if rider participation would justify the cost.
SamTrans purchased the entire Dumbarton Cut-off from Redwood Junction to Newark Junction for US$6,900,000 (equivalent to $11,900,000 in 2019) in early 1994, with the help of a loan from Caltrans. Although the Dumbarton Rail Corridor was almost fully funded in 2001 (the Metropolitan Transportation Commission estimated the total capital cost for the Dumbarton Rail Corridor was US$129,000,000 (equivalent to $186,300,000 in 2019); of that, 91% had been secured or was pending via local sales taxes in San Mateo, Alameda, and Santa Clara Counties), subsequent studies, including the 2003 Dumbarton Rail Corridor Project Study Report, identified several deficiencies in the existing infrastructure. The 2003 Project Study Report proposed replacing the Dumbarton Rail Bridge swing span with a new bascule span, with the option for remote control from the Caltrain operations center or local control; the report also proposed replacing the Newark Slough Bridge swing span with a simpler steel girder swing span under local control, normally left closed to prioritize rail traffic over marine traffic. Other proposed improvements included a proposed fourteen-span bridge over Alameda Creek to separate freight and passenger traffic.
The required improvements to infrastructure drove up project costs dramatically. In 2004, the total capital cost had increased to an estimated US$277,600,000 (equivalent to $375,800,000 in 2019). However, Regional Measure 2 (RM2) was approved by a majority of Bay Area voters in March 2004, raising toll rates by US$1 on the region's toll bridges. US$135,000,000 (equivalent to $182,700,000 in 2019) was allotted to the Dumbarton Rail Corridor project from the increased tolls as one of the headline projects cited by supporters of RM2. In 2008, US$91,000,000 (equivalent to $108,100,000 in 2019) in RM2 funds were loaned from Dumbarton Rail Corridor to BART for work on the Warm Springs Extension. The 2008 estimate for DRC capital costs had risen to US$596,000,000 (equivalent to $707,700,000 in 2019), compared to the nearly US$300,000,000 (equivalent to $406,100,000 in 2019) in available funding that had been committed with the passage of RM2 in 2004, reducing the feasibility of Dumbarton Rail Corridor. The $91 million loan would become a grant in 2014 when the Metropolitan Transportation Commission voted to forgive the terms of the loan. With RM2 funds deprogrammed from Dumbarton Rail Corridor, the project was suspended. Efforts continue to revive the project.
Dumbarton Rail Bridge