First look at BART's 2nd Transbay Tube renderings

The first renderings of what a second Transbay Tube would add to the Bay Area have now been made public. 

One concept, by Amtrak’s Capitol Corridor, now known as Link 21, shows a new BART station at San Francisco's Mission Bay.

Both possible plans have new stations in Alameda, downtown Oakland and Jack London Square. 

Both also have BART extending to the Salesforce Transit Center.

Link 21 is currently working with state leaders to improve the Bay Area's rail network.

The Chronicle reports that the idea is decades away, with a possible completion date of 2040 and an estimated cost of $29 billion.