Transbay Blended Tunnel

Blended Systems Concept

In my previous article, I asked if we could unify our rail systems? Unfortunately, I used the wrong buzz word. The term that everyone is using today to refer to a unifyed solution is “blended“.

As an example of a blended system concept, let’s look at the current proposal for a second Transbay Tube. ^[1] ^[2] The thing I like the most about the current discussions is that they are not talking about another non-standard solution, using BART’s non-standard gauge and equipment.

“We’re not looking at anything as a stand alone project. It’s a statewide project,” added Ratna Amin. By that she means that High Speed Rail, Caltrain, Amtrak, ACE and all regional rail systems that use standard gauge tracks need to be able to use the new tube. “A new tube—it is either standard gauge or it is both.”^[3]

In November 2014 BART presented SPUR with a Vision Update^[4]. It included a proposal to reduce congestion along the Richmond line and the I80/580 Corridor using a high-frequency Diesel Multiple Unit (DMU) service. This service would use the existing Capitol Corridor tracks^[5]. BART Eastshore DMU

Recently, Roland Lebrun placed an addition proposal on the table^[6], to extend that DMU solution through the new Transbay tunnel. He suggests the creation of three new eDMU routes: Martinez to Oakland Coliseum, Oakland Coliseum to Bayshore and Martinez to Bayshore, shown in blue. proposed blended routes The key factor here is that the final product will not be limited to use by one technology, but will be open to use by any of the competing, standard gauge rail lines.

We must also remember that the cost to build such an extension, according to BART, can be as much as 60% less^[7] than an equivalent BART system.

Tunnel Type

The one other thing I would like to mention is the type of tunnel design. I don’t have a personal bias, but I would like two different designs to be considered.

I suspect everyone is assuming the new tunnel would be a twin-bore design, such as Roland Lebrun used in his proposal.I would like to see a comparison made between the twin-bore design and the single-bore design that has been proposed by the VTA for the BART San Jose Phase II project.^[8]

Just for the record, I would like to see the two styles compared for compatibility, cost and safety. After all, I have proposed BART Phase II in San Jose be built as a blended system. It seems to me that both tunnels should share the same architecture. This would allow those building the second one to learn from the experience of the first team.

Going Forward — 100% Blended Designs

Going forward, all new projects must be designed to support any standard gauge equipment. We cannot continue to paint ourselves into corners where system and equipment maintenance expenses become the lead factor in budgeting. The only real decision we need to make is, should the transbay tunnel support single or double-deck EDMUs (EMU/DMU hybrids). As always, I would suggest support for both options. We could start with a single deck service and then add double-deck when the demand requires it. Flexibility is nice and, considering the savings over installing a BART system, affordable.