HSR across the Bay Bridge?

In my recent post introducing rapid rail as a concept, I included a map showing the potential of running HSR trains across the Bay Bridge. This was very tentative, mostly because I did not know if the bridge could support the weight of modern, lightweight UIC-compliant passenger trains.

Early on in its service life, the Bay Bridge used to carry electric trains, e.g. this trolley car from 1938:



In 1959, the rail tracks on the lower deck were converted to road lanes. In 1998, at the urging of their mayors, voters in San Francisco, Oakland, Berkeley and Emeryville passed a non-binding declaration of policy that rail service should be restored. Quentin Kopp, then in charge of the project to build a new east span, rejected the idea out of hand. Bitterly ironic, isn't it? See also the response by Emeryville's then-mayor Bukowski.

Nevertheless, MTC did commission a rail feasibility study that was published two years later. It concluded that sacrificing road lanes would not be acceptable due to an expected 22% increase in persons crossing the bridge by 2020. This was a complete non-sequitur, since a rail track can support a lot more person crossings than a road lane. Rather, the statement should be seen as evidence of the clout of the road lobby.

The study did conclude that rail tracks could be added to the west span, either slung underneath (subject to Coast Guard approval) or, on ugly cantilevers on either side. However, the cost for getting the western span "rail ready" in this way was estimated at almost $1.33-1.45 billion, excl. the actual tracks and western approach from the new TTC. With an underground train box there, only the (cheaper) alternative of tracks slung underneath the bridge was considered possible.

The new east span was designed to support five lanes of road traffic in each direction, plus emergency and wide bike lanes. Back in 2000, the design consisted only of the two skyways. The feasibility study concluded that the design of those structures would could support light rail, but only if the inside lanes were sacrificed. The outside lanes would have been preferable in terms of tunnel construction at Yerba Buena. Modifications to add light rail tracks were estimated at $546 million, provided the design changes were made before breaking ground.

All told, MTC study estimated a cost north of $3 billion just to get entire bridge and its approaches ready for two tracks of light rail plus five active road lanes in each direction. This was considered far too expensive at the time, so all rail services were dropped from consideration. The self-supporting suspension span that was added to the new east span at a later date for aesthetic reasons was probably not designed to support light rail.

For reference, the axle load of the latest generation of European bullet trains is below 17 metric tons. That's not much higher than the maximum permitted load on the rear axles of an eighteen-wheel heavy duty truck, 34,000 lbs (15.4 metric tons). In terms of weight per linear foot of track, a measure relevant for bridge loads, the FRA-compliant Acela Express comes in at a hefty 1800 lbs/ft. However, a fully decked out Alstom AGV comes in at 1370 lbs/ft, a shade below light rail at 1390 lbs/ft!

Competitive HSR products are at similar or slightly higher values, BART at lower ones. That suggests running either BART or HSR trains across the Bay Bridge just might well have been possible at reasonable cost, provided that road lanes had been sacrificed for the purpose. Otherwise, it would make more sense to build a second transbay tube one day, e.g. under Oakland harbor via Point Alameda.

Unfortunately, with the construction of the east span and the seismic retrofit of the western approach already underway and, the Transbay Terminal project set to break ground, it seems highly unlikely that bullet trains will ever cross the Bay Bridge.