Last week blogdowntown reported the final two options for the 1.5-mile Regional Connector that will provide a one-seat ride into and across downtown between the Blue / Expo Lines and the Pasadena / Eastside Gold Line.
These images (click to enlarge) are updated from Metro's February presentation. (Turns out my suggestions last November didn't work structurally to connect with the existing Gold Line bridge at Aliso.)
In Alternative 3B the existing Flower Street tunnel would be extended up to street level at 4th for a station, cross 3rd at-grade, cut through the 2nd Street tunnel wall, then run on the south side of the tunnel and middle of 2nd (image below). A one-way couplet on Main and Los Angeles completes the route up to Temple and the Gold Line.
Alternative 5 is a subway extension up Flower and beneath 2nd Street. It would ramp up from a portal at 2nd and Central across the Office Depot lot to cross Alameda at-grade. Alameda would be depressed below 1st Street.
This rendering shows the proposed at-grade alignment on 2nd Street. It does all fit in the 60' street right-of-way (5' sidewalk, 10' station platform, 24' trackway, 11' traffic lane, and 10' sidewalk).
But detailed study and the relatively-small price difference — $650 million vs. $800 million — is likely to conclude that the subway is the best choice, for a faster ride with less traffic and train disruption.