Running
Caltrain down the middle of the peninsula corridor, with
HSR tracks flanking it on the outside, would maximize operating flexibility. For both
HSR and
Caltrain, the many pros and few cons of this "fast-slow-slow-fast" (
FSSF) configuration were
discussed before. In this configuration, each
Caltrain station would have a single central island platform accessed via stairs, ramps and/or elevators from grade-separated streets or pedestrian tunnels running underneath and perpendicular to the tracks.
The archetypal
Caltrain station would consist of a 750-foot island platform (sufficient for 8-car trains), 30 feet across at its widest point. The tracks would slew apart and drape along either side of the platform along a gentle curve, with the platform tapering slightly at its ends. The technical term for such a track arrangement is a "wow" around the platform. Pedestrian access in the form of stairs and ramps could be built beyond the ends of the platform. Seen from above, the arrangement would look vaguely like an elongated football--hence the name, Football Island.
On Football Island, the typical station amenities would be shared among both northbound and southbound directions. One set of ticket vending machines, passenger shelters, benches, lighting, visual information displays, etc. would suffice to serve both directions. The platform space itself would be about twice as wide as today's
Caltrain platforms, providing a safe space for waiting passengers well away from any trains that might speed past the platform without stopping. Access to and egress from the platform would occur at both ends and near the middle (total 3 places) to provide a safe waiting space without confined dead-ends. More people would be present on a platform that serves both directions, so passengers would be less likely to feel isolated or unsafe.
Underneath Football Island, cross streets (as typically found near
Caltrain stations) would pass under the station, typically near the ends of the platform--although the design is flexibly adaptable to any local street configuration. Bus stops would be located right underneath the platform, allowing connecting passengers to switch between bus and train via a single flight of stairs (or a single ramp) without ever needing an umbrella during rainy season.
The station would connect into the pedestrian fabric of each town with six different approaches (3 paths under the tracks, each accessible from east and west.) There would never be any confusion as to which platform to wait on, and clear signage on the platform and trains would indicate the correct service direction to new users and regular commuters alike.
Football Island would be replicated at every
Caltrain station for a consistent look and feel, with minor variations to accommodate the local street configuration.
Yes But...The Football Island concept does not fit the stereotype of what an American commuter rail station looks like. That's why the people in charge of designing new stations for the peninsula corridor might initially be suspicious of the idea. Here is a list of objections they might raise.
- Platforms must be tangent (straight) to meet ADA regulations.
In today's regulatory environment, "curved platform" might seem like an oxymoron. Just like a turning semi-truck needs additional clearance on the inside of the turn, long train cars serving a curved platform need a wider gap to clear the edge of the platform. This eats into the maximum 3-inch gap permissible under ADA regulations. By how much? Football Island would be built on such a wide curve radius (10 km / 6 miles) that an 85-foot passenger car would have a maximum lateral displacement of 4.5 mm (3/16 inch), which amounts to just 1/16th of the permissible gap. For ADA level boarding purposes, Football Island is essentially a tangent platform. Unfortunately, the specifications for HSR (TM 2.2.4 section 6.1.3) limit platform curvature to a minimum of 20 km / 12 miles, and only under exceptional circumstances requiring special approval.
- HSR passengers would be uncomfortable with all the twisting and wowing around Caltrain stations. Straight tracks are necessary for a smoother ride.
The 10 km curve radius (zero-degree, ten-minute curve in ancestral railroad units) is very gentle for the 200 km/h (125 mph) maximum speed envisioned on the peninsula. The curve could be fully compensated by less than 50 mm (2 inches) of superelevation on the outside pair of HSR tracks, something exceedingly unlikely to cause discomfort or motion sickness, let alone spill anyone's coffee. The inside tracks for Caltrain would not need any superelevation at all. Again, unfortunately, the specifications for HSR (TM 2.1.2) state right up front that "Over four changes in direction per mile shall constitute an Exceptional condition." That's all well and good at 220 mph, when a mile flashes by in 16 seconds, but this standard is overkill at a more sedate 125 mph.
- Curved track is more difficult and expensive to maintain than straight track.
For card-carrying AREMA members accustomed to laying out freight tracks, this principle may hold true. Not so for high-speed passenger rail: the precise alignment and maintenance required to operate at 200 km/h (125 mph) is equally demanding on straight track and curved track. As to complexity of the alignment, we can safely say that ancestral 100-foot chains have been replaced by lasers, GPS and computer-driven tamping and lining machines that can dress track to millimeter accuracy, regardless of whether it is straight or ever so slightly curved as in the case of Football Island. The wheel-rail interface won't know the difference between tangent track and a 10 km (6 mi.) radius curve driven at just 200 km/h (125 mph); additional wear will be nil.
- Football Island would require much more land, to provide clearance for the tracks to wow around the platform.
Not that much more.
Compared to a traditional arrangement with 16-foot outside platforms (blue lines), Football Island (red lines) requires 2220 m2 (24,000 square feet or 0.5 acres) of additional space. This extra space is shown by the area shaded green in the figure at right, assuming that the right-of-way boundary is 4.5 m (15 ft) from the nearest track center line.
Compared to yet another candidate configuration, a one-sided wow with three straight tracks and one track wowing around an island platform with a radius tightened to 7.7 km (to account for slower commuter train speeds), Football Island uses about 0.2 acres less land. See figure at left; the blue side-wow configuration uses additional area shaded green, minus the portion shaded gray. The green area is larger than the gray area, showing why the side-wow configuration uses more land than the Football Island configuration.
- Placing an island platform between the tracks impedes passenger access.
While an island platform indeed prevents direct access along its entire length from the local area around the station, consider that a typical Caltrain passenger will use the same station twice per trip: once on each leg of the journey, using the northbound and southbound platforms once each. Therefore, even with outside platforms, the passenger must use grade-separated undercrossings on at least one leg of the journey. If you tally the number of stairs and the distance walked through access facilities on a roundtrip journey--an objective measure of accessibility--Football Island is no worse than a grade-separated conventional outside platform, especially if the station is elevated.
- Nobody else does it that way.
Anybody in Silicon Valley would tell you that's no reason to be afraid to innovate. Nevertheless, there is a precedent as shown in the opening photo: the FSSF configuration with island commuter platforms is used to great advantage in Stockholm, Sweden, where the 200 km/h (125 mph) non-stop Arlanda Express runs on the outside tracks, with local commuter service on the inside tracks with island platforms. The photo above was taken from about 1:40 in this video. Another video shows an amazing side-by-side race with an Arlanda Express, shot from the cab of a commuter train; note crossovers providing access between slow and fast tracks.
The Football Island concept deserves serious scrutiny for the Analysis of Alternatives process currently underway for the peninsula rail corridor, and it should not be dismissed out of hand just because a couple of poorly conceived requirements stand in the way.
Football island would enhance the peninsula commute while ensuring the smooth flow of local and express traffic, without requiring hulking flyover structures or stacked arrangements to provide flexible access between slow and fast tracks.
The tree survey includes a detailed tree-by-tree assessment of some of the densest tree canopies along the rail corridor, such as Atherton and Burlingame. It also includes a mile-by-mile summary of vegetation intensity on each side of the corridor, graphed in the figure at right. 1 = generally clear, 2 = scattered or intermittent, and 3 = dense with long stretches of continuous canopy.
One possible way to quantify the relative HSR impacts to trees along the rail corridor is to combine the vegetation intensity index with the corridor width from San Francisco to San Jose. It's an interesting exercise because more trees will be impacted where the corridor is narrow. Take the sum of the vegetation intensity on both sides of the corridor, subtract two (so that we don't count "generally clear" areas), and simply divide by the width of the corridor. This is the formula for a Vegetation Grief Index (VGI), which is highest when the corridor is narrow and the vegetation is dense. The result is shown at left.
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