Diridon Delusions

San Jose is striving to redesign and expand its Cahill Street station, named for the (still living) former Santa Clara County board of supervisors chair Rod Diridon, to meet the needs of future rail service including BART and high-speed rail. The station's context was discussed here in 2017.

The process led by the Joint Policy Advisory Board, made up of representatives from the city and relevant transportation agencies, has now reached the key juncture of presenting a small number of alternatives to the public. Before we dig into this, let's pause to consider an alternate plan.

The HSR Environmentally Cleared Project

This design is already
environmentally cleared.

The California High-Speed Rail Authority, as part of its San Jose to Merced project, has already obtained full federal and state environmental clearance to build the simple Diridon station concept shown at right. This plan adds a couple of overpass mezzanines above the existing platforms, and rebuilds two of these platforms for compatibility with high-speed trains, using the newly established standard height of 48 inches above top-of-rail and lateral offset of 73 inches from the track center. The 48" x 73" platform standard was agreed in June 2023 between the Authority, the FRA, and other prospective high-speed rail operators such as Brightline West. Due to budget pressures, the HSR project took a rather minimalist approach to this station, electing to build it at grade within the footprint of the existing facility, but pledged to work harmoniously with other agencies on more ambitious concepts. Think of it as a minimum viable product that has already cleared CEQA and NEPA, before we turn to what is now brewing for San Jose.

The Diridon JPAB Alternatives

In any public alternative evaluation process, it is important to carry a sacrificial alternative. This serves the same role as an unlikable character in a movie, whose demise is heavily foreshadowed and brings relief to the viewer when it occurs. The sacrificial alternative can be eliminated in an overt display of due diligence, reassuring the public that the authorities are being thrifty and mindful of the interests of riders and taxpayers. In this case, the "stacked" alternative seems to serve this purpose, and warrants no further discussion because it will shortly be eliminated.

Note similarity of elevated and at-grade options.

This leaves a choice between two alternatives known as "at grade" and "elevated," actually a distinction without much difference. Both designs are driven by an overarching requirement to create an expansive concourse level below the tracks and platforms, purporting to imitate grand European train stations but far more likely (this is America!) replicating the airport experience for train passengers. Early architectural renderings show this as an open and airy space resembling an Apple Store, paying no heed to the fact that the sky will be completely obstructed by tracks and platforms built on a dense forest of beefy concrete columns. No matter how pretty the architects try to make it, this will be a heavy elevated structure built on alluvial soils near seismically active faults. The light-filled and soaring station canopy will be enjoyed by nobody for any length of time, since all waiting areas will be in the basement.

Things to Watch For

The effectiveness of a station modernization project should be measured by its operational efficiency. The primary focus should be on shaving seconds off travel times, to include:

• Removing slow zones in the station approaches. On the north side, this means removing the CEMOF double reverse curve, a self-inflicted obstacle added in 2005 that limits all trains to 40 mph over a mile before the station. Main tracks MT2 and MT3 should be restored to their former alignment on the west side of the maintenance facility, with a flatter curve allowing trains to pass the facility at higher speeds. On the south side, this means greatly increasing the speed limit between San Jose and Tamien, currently just 35 mph, and providing at least two electrified tracks.
   
  
• Re-configuring the layout of north and south station interlockings (a.k.a. "station throats") to enable swift and parallel train moves into and out of the station, on turnouts rated for much higher speeds than 15 mph of the current layout. Nobody in Europe or Asia would accept a train crawling slowly along a platform while dinging insistently; trains arrive and depart swiftly and quietly.
  
  
• Ensuring that all Caltrain traffic will shoot through on just two platform tracks and one island platform. Despite the "south terminal" school of thought still prevalent at Caltrain headquarters, San Jose Diridon should become just another intermediate stop on the way to further destinations in the greatly under-served but densely populated southern parts of the city, which the BART-fixated county agency seems to have completely forgotten about. A great way to sell this extension would be as a "South San Jose to BART Regional Connector Project." Cutting Caltrain's footprint to just two tracks and one island platform will free up ample space for other operators.
  
  
• Providing excellent vertical circulation, which means short vertical circulation. This is one benefit of putting the concourse under the tracks: people are shorter than trains. Architects should resist the urge to make the ceilings in the passenger concourse vault too high because this needlessly extends the reach of stairs, escalators and elevators. Likewise, structural engineers should resist the urge to put the tracks on top of enormous concrete box girders. The early concept renderings show 15-foot ceilings with 9-foot structure depth, while 12-foot ceilings and 3-foot structure depth (using through-girders) would bring the entire structure 9 feet down. This saves every single passenger ten seconds of vertical transport, worth an hour per year for each commuter! Don't go for drama, go for ruthless efficiency: form must follow function.
   
  
• Providing a straight-shot escalator / elevator ride from the north end of the Caltrain platform to the west end of the underground BART platform. This simple shortest-path connection avoids a long and circuitous walking detour through the main BART entrance, located outside and east of the station footprint. Please don't let agency turf lead to lengthy and confusing transfers.
  

The unifying theme here is to save passengers time, whether on the train or in the station. Every second of the San Jose travel experience matters. A counter-intuitive fact about high-speed rail is that the best way to save time is to relentlessly focus on speeding up the slowest bits, like station approaches and escalator rides. In terms of capital costs, those are by far the cheapest seconds to save. California has already committed to the enormous expense of building a 220 mph system, and San Jose is not the place to wastefully undo those hard-won time savings.

If operational efficiencies are not realized in San Jose, and the opportunity to bring the station into the 21st century is not captured, then we'll end up with a new multi-billion dollar train basement that does little to improve regional transportation.