It's the Trip Time, Stupid

Components of trip time.
Electrification only improved
time in motion. Photos by
Mliu92, Evan0512, SaarPro.

Marco Chitti recently penned a great piece about Why Speed Matters, a critique of Toronto's recently opened and glacially slow Finch West light rail. It echoes some of the themes that have infused discussions about how best to improve Caltrain, and what to focus on next. Electrification had obvious speed benefits that have now been realized, resulting in a ridership boost recently recognized by an industry group as "America's Fastest-Growing Transit Agency." But what now? As the accolades die down and the catenary fades into the scenery, will Caltrain lose its sense of purpose and fall asleep on its laurels?

Their relentless focus must remain on trip time, which comprises more than the time in motion, the component of trip time that was so remarkably improved by electrification. Trip time also includes time at rest, made up of all those station dwell times, and time waiting for the train, which depends on service frequency. The peninsula rail corridor's entire capital program should be organized around reducing trip time; instead, we see attention and funding being scattered among an incoherent set of gold-plated projects that produce no discernible trip time improvements:

• stupendously expensive grade separation projects such as Broadway in Burlingame ($615M to $889M) or Rengstorff Ave in Mountain View ($395M to $453M) masquerading as train projects are actually massive road traffic sewer expansions that provide negligible benefit to the average train passenger, especially after Caltrain recently demonstrated major reductions in cars-on-tracks incidents.
  
  
• like the White House ballroom, a grandiose remodel of the San Jose station (the "Diridon Integration Station Concept Plan") will plow under (literally!) 3 to 6 billion dollars to over-deliver on Caltrain's need for a single island platform at this not particularly remarkable train stop.

None of these shameful nine- and ten-figure megaprojects do anything to attack the components of trip time. To improve trip time, these are the projects that actually matter, in order of small to large:

1. Fixed EMU door software to reduce each station dwell time by about ten seconds (the cost rounds to zero, serving as a useful litmus test of Caltrain's faith in trip time). Reduces time at rest.
    
2. Updated EMU step design, a prerequisite for the transition to level boarding. The prototype cost is $3M and fleet-wide deployment likely less than $10M. This is currently the most important capital project at Caltrain, whether the college intern assigned to it knows this or not. Enables future reduction of time at rest.
    
3. Twenty-minute base frequency, improved from today's half-hour, when the fleet grows to 21 (reliable!) trains. The capital cost is ~$0.4B but is already sunk. This adds operating cost, but only marginally since Caltrain has high fixed costs that can be better amortized over more riders. Reduces time waiting.
    
4. Level boarding, not as a consultant-bloated megaproject where all platforms are replaced, but as a simple and incremental project using the existing platforms as foundation slab with modular, lightweight elements added to raise the height up by two steps (14 inches). This is likely < $0.5B system-wide and reduces time at rest.
    
5. The four-track hub station in Redwood City, preferably with quadruple approach tracks (for simultaneous local+express arrivals and departures) from CP Dumbarton to San Carlos. This is the only grade separation project on the corridor that has any value for trip time. This one is likely about $1B. Reduces both time at rest (for the local being overtaken, thanks to the quadruple approach tracks) and time in motion (via cross-platform transfer to/from an express).
    
6. The SF downtown extension, another dazzlingly expensive megaproject that will only be worth its cost (>$10B) if San Francisco downtown office towers fill up again, if service is extended through a new Transbay Tube to destinations eastward as part of Link21, and if the federal government ever funds big transit projects again. Compared to a two-seat ride, a direct connection reduces time in motion, time at rest, and time waiting for a transfer.

Ridership and revenue follows from trip time, another way of saying that time is money. All other capital projects are at best value-maintaining, not value-adding.

Note: Trip time forms the basis of timetable scoring in the Taktulator, with the nerdy details laid out in the formulation of a service quality metric and the posts linked therefrom. Reading this material over a decade later, it still rings just as true.

Capital Spending for Better Service

Wouldn't it be great if you could quantify the service benefit of capital improvements, to compare and prioritize them by how much better train service results?  We can, and using our handy Taktulator, we will. This service pattern evaluation tool was formulated around time-based service quality metrics. We use it to explore future improvements to the peninsula rail corridor.

Today's 2022 Timetable: 94 service points -- The current peak schedule with four diesel trains per hour features very generous padding and SF - SJ trip times ranging from 66 minutes (express) to 99 minutes (local). The less-than-100 score indicates that service quality has dropped since 2011 when there were five trains per peak hour. The Taktulator score is calibrated such that the 2011 Caltrain timetable scores exactly 100 points.

Caltrain's 2040 service vision foresees eight trains per peak hour per direction (not counting HSR). Let's start with a service frequency of 8 trains per hour-- except for the sake of exploring and quantifying the value of capital improvements, we'll start from a hypothetical case that will never happen: eight trains per hour of today's diesel service, making all local stops.

Hypothetical diesel all-stops local, 8 tph: Score = 109 service points (+16%) -- The doubling of hourly frequency improves the service score by 16%, despite each train being slower. The extra time riding an all-stops trains is more than offset by the much shorter wait time at the station. For example, maximum wait times in Belmont plummet from one hour to just 7.5 minutes. Unfortunately, this service pattern would take an unrealistic 32 trains to operate, because each train takes 94 minutes to go between SF and SJ. The hypothetical scenario still illustrates the magnitude of the effect of doubling frequency.

Add electrification: Score = 121 service points (+11%) -- Electrification is worth another +12 points relative to diesel, thanks to the shorter trip times that come from the higher acceleration capability of EMUs. Those savings accrue to a full ten minutes between SF and SJ for an all-stops local. Station dwell times are still booked at 45 seconds, a longer duration that reflects the lack of level boarding. Thanks to the faster trip times, the fleet requirement has dropped from 32 trains to 28 trains. Service speed saves money, not just on fleet size but also by increasing the hourly productivity of train crews (in terms of passenger-miles served).

Add Redwood City hub station: Score = 131 service points (+8%) -- If trains cannot pass each other, there is no room in such a frequent timetable for express service. A new four-track station at Redwood City, where express trains can overtake locals on opposite sides of the same station platform (so that passengers may transfer seamlessly between local and express) gives the best of both worlds: frequent service AND express service. For now, we'll assume this station has only two-track approaches, requiring trains to arrive and depart serially. In practice, this means every local must wait more than 5 minutes or the equivalent of two signal headways to let the express catch up before RWC and then pull ahead after RWC. The stopping patterns start to look like Caltrain's 2040 service vision.

Add Redwood City quadruple approach tracks: Score = 138 service points (+5%) -- If quadruple tracks are added approaching Redwood City from the north and south, then local and express trains can make parallel moves into and out of the hub station, removing the requirement for every local to wait there for five wasteful minutes. To unlock this benefit, the quadruple track overtake section needs to extend to one station on either side of RWC, so every local train can make productive use of those five minutes. In the Taktulator, we simulate this by having every local train stop at San Carlos and Atherton, which (despite its closure) stands in for a new Fair Oaks infill station at 5th Avenue. This suggests a hub station is about 1.7x more effective if it forms the center of a three-station quadruple track section. Having fully half your trains save five minutes is a huge service improvement!

Add level boarding: Score = 147 service points (+7%) -- Where electrification saved time in motion, level boarding saves time at rest by shaving 15 seconds of dwell time at each station, as step-free access smooths passenger boarding and alighting. Level boarding gives not only short dwell times but predictable dwell times (for example, wheelchairs don't take longer to board) so we can also tighten up the padding margin in the timetable, cut in this example from 12% to 7%. Interestingly, the end-to-end corridor times fall below a threshold that allows turning a train sooner, reducing fleet requirement from 28 to 24 trains. This isn't necessarily an effect of level boarding itself, and only illustrates that a series of small improvements can result in a discontinuous benefit when a certain threshold is reached.

Add SF Downtown Extension: Score = 250 service points (+70%) -- There are more jobs (over 100,000) located within a half mile of the Transbay Transit Center than there are jobs within a half mile of every other Caltrain station combined. This makes downtown SF a dominant node if added to the system, a fact that is reflected in our census-based weighting of available trips. No other improvement comes close.

Here is how these service improvements stack up against each other, plotted as the logarithm of the ratio of after/before scores, which gives you their relative impact. They can be constructed in a different order than imagined above, but the relative proportion of each improvement should remain approximately similar:

Bar graph of the relative service quality improvement of Caltrain capital projects

Here are some key takeaways:

1. Grade separation projects do not improve train service. Exceedingly rarely, they do prevent a train delay, something that is not captured in this analysis. On the basis of the time metrics of a typical trip, however, the service improvement of grade separations is ZERO. This should factor strongly into how many billions we are collectively willing to spend on them relative to the other capital improvements discussed here.
    
   
2. The benefits of electrification alone (without other improvements) are mediocre at best. On the basis of our time metrics, service quality is only improved by about 11% relative to an equivalent diesel scenario. Caltrain can't just finish the electrification project and call it good enough.
    
   
3. The Redwood City hub station now in the planning stages is surprisingly beneficial to service quality. While packaged and sold as a grade separation with a bonus of expanding the train station, it is hard to overstate the service quality benefit of the new hub station. Even as planned by Caltrain (with two-track approaches from the north and south) the new station produces nearly as much service improvement as the entire electrification project.
    
   
4. The Redwood City hub station as planned by Caltrain with two-track approaches is operationally ineffective. It can be juiced up to 1.7x more benefit to service quality by making it the center of a four-track overtake facility spanning just three stations: San Carlos, Redwood City and a new Fair Oaks infill station at 5th Ave. The southern portion of this four-track facility already exists today. Together with 4-track approaches, the Redwood City hub improves service quality by a greater proportion than the entire electrification project! That's why it is critical that planning for the Redwood City grade separations allow for four tracks throughout.
    
   
5. Level boarding provides over half the service quality improvement of electrification, and is likely to be a much cheaper capital investment. However, it makes sense to do it after the hub station.
    
   
6. The downtown extension in San Francisco will be a game changer for service quality. The transportation industrial complex knows this and will make us pay dearly for the DTX project. However, the additional billions for the PAX (Pennsylvania Avenue Extension, a city-desired grade separation) add absolutely nothing to service quality, and should never be allowed to be bundled with the DTX project. Every capital dollar should improve service quality.
    
   
7. The Redwood City hub station (with four tracks, not two!) is worth one fourth of the service benefit of the DTX. That means we should (a) not be shy about spending capital dollars to build it and (b) stop selling it as a grade separation, because that isn't the story here-- it should be about a new infill station, seamless transfers, and better service quality system-wide.
   

As always, the analysis provided here can be quibbled with and improved upon, and you are encouraged to "do your own research" by trying out your own service patterns in the Taktulator.

Redwood City Grade Seps: We Must Do Better

The first preliminary engineering plans for the downtown Redwood City grade separations are out. This isn't your average grade separation: it underpins the most important new piece of rail corridor infrastructure that will enable future Caltrain service to be much better than it is today. Redwood City will become the main overtaking location for Caltrain, with a cross-platform transfer between local and express trains at a new four-track station. We had previously looked at Redwood City issues and laid out the design values that will make Redwood City a high-functioning station.

There are four grade separation alternatives on offer, as described in the overview video:

1. Fully elevated all the way from Whipple to Highway 84
2. Partially elevated, in two phases, with Jefferson rebuilt in phase 1
   
3. Partially elevated, in two phases, with Jefferson rebuilt in phase 2
   
4. Partially elevated at Whipple, with everything else staying at grade
   

If you're going to be driving a car, the good news is that the designers have done a fantastic job with the car infrastructure, with an A+ on road and intersection design. Unfortunately, this is a grade separation first and a train station second, almost as an afterthought. It should be a train station first. To understand why, let's look 20 years ahead.

Better Service for Many More People

In 2040, which sounds futuristic but is relatively soon, rail service in Redwood City is far better than was ever imagined in the depths of the pandemic of 2020. Here's what is happening:

• Frequent peninsula rail service. As planned in Caltrain's service vision, electric trains serve a vibrant downtown Redwood City with all day half-hourly service and up to eight trains per hour per direction during the morning and evening peaks, equivalent to adding 5 new lanes to Highway 101. Except it's centrally located, it's quiet, it's emission-free, and it's faster than the hordes of electric autonomous cars gridlocked on 101. At the new elevated four track station, every 15 minutes, in each direction, a local and express train stop side by side on opposite edges of the same station platform. Express passengers who are going to minor destinations transfer to the local, and local passengers going to major destinations transfer to the express.
   
  
• A new station at North Fair Oaks. Following the closure of Atherton station, eliminated for lack of ridership in 2020, a new Fair Oaks station has been created near Fifth Avenue and the southern end of the four-track segment through Redwood Junction. Perfectly spaced halfway between Menlo Park and downtown Redwood City, this station serves neighborhoods that are among of the most densely populated along the entire peninsula rail corridor. The 2010 census showed more than 15,000 jobs and 35,000 historically disfavored residents within a 1-mile radius, and the area has flourished since then with new rail service. Not only is Fair Oaks a significant source of new ridership and revenue for Caltrain, but it is served with zero additional trip time and train operating cost. We will discuss below how this feat of magic is pulled off.
   
  
• New Dumbarton rail service. Inaugurated in the 2030s and using a new Dumbarton rail bridge to the East Bay and beyond, fast half-hourly rail service is relieving regional congestion and making commutes more pleasant and productive. The Dumbarton rail corridor joins the peninsula rail corridor at Redwood Junction, where it merges without interference to peninsula train traffic to create an efficient transfer with Caltrain at the bustling station in downtown Redwood City.
   
  
• Statewide high speed rail service. While Redwood City was not considered a viable station stop in the late 2010s when the statewide rail network was planned, in 2040 it's a no-brainer to connect to it. Redwood City's focus on growth, connectivity and equity has allowed it to outshine more ossified and backward-looking locations like Palo Alto that once embodied the dynamism and innovation of the region. For this purpose, the platforms at downtown Redwood City are 1300 feet (400 meters) long to accommodate double-length high-speed trains.
  

Focusing on the track layout, the common thread of these four improvements to rail service is the quadruple tracks through downtown Redwood City, connecting the new four track station to the four track segment at Redwood Junction / Highway 84 built at the turn of the century. These quadruple tracks enable parallel train movements into and out of the Redwood City station, making optimal use of the 80-foot width of the rail right of way. This four track layout brings us back to the downtown grade separation project being planned twenty years before, namely now.

The Fatal Flaw

None of the Redwood City grade separation alternatives allow four tracks all the way through downtown. What's worse, the two-track layouts of all four alternatives are wasteful of the scarce and valuable downtown right of way, making no allowance for adding these critically important station approach tracks later. These tracks are required for two very important operational reasons:

1. Approach tracks allow parallel and independent train movements into and out of Redwood City from the Dumbarton rail corridor without introducing train path dependencies, and thus time keeping vulnerabilities. A train from San Jose should be able to approach the station in parallel with a train from Union City.
    
   
2. Approach tracks allow efficient overtakes, supporting a better implementation of Caltrain's future service vision. Four tracks allow local trains to serve Fair Oaks instead of wasting six to seven minutes at Redwood City waiting for an express to overtake them. A similar operations concept is possible to the north, if San Carlos station is rebuilt with four tracks.

We mentioned earlier that service to Fair Oaks could serve many people and generate new fare revenue in exchange for zero additional crew labor and equipment cost. How is this magic even possible? Let's compare two operating scenarios:

Scenario A. In Caltrain's service vision, express and local trains overtake each other every 15 minutes at the downtown Redwood City station, which will have four platform tracks to allow convenient cross-platform transfers. Unfortunately, with two-track approach bottlenecks from the north and south, trains must enter and leave Redwood City sequentially. That means the local arrives first, waits three minutes for the express to catch up and arrive behind it, then waits another minute for the express dwell time, then waits another couple of minutes for the express to leave and pull far enough ahead. Only after six or seven minutes, even if everything is running perfectly on time, can the local leave Redwood City. Sitting still at a red signal is operational poison, wasting passenger time (all the more so because the perception of delay time is magnified more than 2x by immobility) and driving up crew labor costs ($/passenger-mile). Meanwhile, there is no rail service for Fair Oaks residents, and a long gap in Caltrain coverage between Redwood City and Menlo Park.

Scenario B. The express overtake occurs on a passing section with one or more stations served only by the local. The deceleration time, dwell time, and acceleration time associated with that extra local station stop allow the express to gain on the local while the local is being useful and providing service, instead of just sitting around for an interminable dwell at Redwood City. In the southbound direction, the local arrives in Redwood City, waits three minutes for the express to arrive, exchanges passengers, and leaves the station at the same time as the express. The two trains run side-by-side until the local stops at Fair Oaks. By the time it's ready to go again a couple of minutes later, the express is long gone and no additional waiting is required. The overtake took the same overall time (six or seven minutes) as Scenario A, but used the time productively to provide local service every 15 minutes at a new station serving 35,000 people within a 1-mile radius, at zero additional crew labor or equipment cost.

Here's what the track layouts look like, with station distances roughly to scale, comparing the current condition with Scenario A (planned grade separation configuration) and Scenario B (with Fair Oaks station):

Bonus points are awarded for leaving sufficient room to run a fifth grade-separated track from the southbound tracks to the Dumbarton corridor, flying over Highway 84, as shown in the last panel. This allows seamless merging of the two corridors, without the two streams of rail traffic fouling each other on the way to and from downtown Redwood City. The right time to plan for this is now, not after we pour concrete in the wrong place, even if the funds aren't yet available and there isn't yet a viable Dumbarton project.

Layout of new Fair Oaks station, roughly to scale

Here's what the new Fair Oaks station might look like, near milepost 27. It's about 100 feet wide in an area where the corridor is only 80 feet wide, so it will require taking nine properties along William Avenue. While taking residential properties in a less advantaged neighborhood of unincorporated San Mateo County is never desirable, this must be weighed with the wider benefits to the 35,000 residents of North Fair Oaks and other neighborhoods within a one-mile radius. A narrow slice (~10 feet) of land would be required to be taken from backyards along the opposite side, to make room for the southbound platform. The site has good pedestrian and bus access via Fifth Avenue, and a new pedestrian underpass would connect Berkshire Avenue across the rail corridor, improving neighborhood connectivity. The new Fair Oaks station is very low hanging fruit that can make Caltrain serve more people more efficiently from day one of the new service vision.

The marginal cost of building the grade separations with the additional tracks now is small relative to doing it later, so why would we delay such an important operational improvement or waste money re-doing it twice?

Not allowing for quadruple approach tracks is the fatal flaw of the downtown Redwood City grade separation project. All the alternatives feature two-track bottlenecks that fail to adequately support Caltrain's service vision and impair the future Dumbarton rail corridor service, which is especially concerning because Caltrain and the San Mateo County Transportation Authority seem to have directly participated in the design.

Here are some other comments on the various alternatives:

The Good

• The roads and intersections and turn lanes and all the car stuff is perfectly designed for smooth and unimpeded car operations.
   
• All alternatives feature the four track station, consistent with Caltrain's future service vision, which calls for Redwood City to be the location where express trains overtake local trains.
  

The Bad

• All the bridge structures have porky structure depths, ranging up to 9 and even 17 (!!) feet. Every foot that your bridge deck is thicker is a foot that the entire edifice, including all embankments, will be taller. In this case, each extra foot of structure depth is worth about 1,500 18-wheel dump truck loads of dirt to fill the embankment one foot higher! Thicker structures also push roads to be depressed more deeply into the ground, which exponentially increases excavation and utility relocation costs. Thicker bridges at stations needlessly extend stairs and ramps. For the love of Redwood City, use thinner structures! Previous grade separations, such as the one in San Bruno, have used steel beams to keep the structure depth (from soffit to top of rail) to about 5 1/2 feet for an ~85 foot span. Through bridge designs can be even thinner. Grossly excessive concrete bridge structures as seen here are an unmistakable symptom of not caring about costs and impacts.
   
  
• Enormous extra costs are being incurred at the southern end of the grade separation by not allowing the vertical curve at Highway 84 to begin until north of the overpass and the existing turnout, and then limiting the grade to only 1%. This is lazy paint-by-numbers engineering that blindly applies design standards without regard to their consequences, which in this case push Chestnut Street and others much deeper underground than is necessary. If there ever was a case where an exception to Caltrain design standards was warranted, this is it. Using a 2% grade and starting the vertical curve south of Highway 84, squeezing every inch of available vertical clearance under Highway 84, will save millions. In a modified Alternative 1, Main and Maple may not even need to be sunk at all.
   
  
• The platforms are 900 feet long, and there may not be sufficient clearance left between the station tracks to extend them to 1300 feet (400 meters) later to support high-speed rail service at Redwood City. While this is not in current official plans, it makes sense and it would be a shame to preclude it. There is plenty of room in the site to allow it.
   
  
• The station should be open underneath, not built on a filled embankment. It should allow a future Broadway light rail line to shoot straight through, right under the Caltrain platforms. As proposed, all the alternatives torpedo the city's Broadway street car project.

The Weird

• The vertical profiles have unusual constraints on vertical curves, seemingly not allowed over or under bridges. That is just silly and grows the embankments unnecessarily taller.
  
  
• Hopkins Avenue should be re-connected across the tracks. It's basically a freebie to improve neighborhood connectivity.
   
  
• All alternatives, not just 2 and 3, should start near Howard Avenue in San Carlos, extending a four track station approach as far north of Whipple as possible. In the future, if the San Carlos station is rebuilt as a four track overtaking station, dwell times at Redwood City can be further shortened than is possible with just the Fair Oaks station, using the same overtaking principle.
  
  
• Pennsylvania Avenue is treated as a city street, not the encroachment on critically important railroad right of way that it actually is. It will be needed anyway for temporary shoofly tracks during construction. The grade separation project should not give away valuable railroad right of way to automobile uses.
   
  
• Alternative 4, at grade, has no clear way to access the station platforms and forms an even more formidable barrier through downtown, seemingly in contradiction with project goals.
  

The Redwood City grade separation is about much more than just grade separating roads to make traffic flow freely. Like any project on the rail corridor, it needs to be planned and built not only such that future improvements to rail service aren't made more difficult or impractical, but to start putting in the hooks for those improvements now. The marginal costs aren't zero, but they're so much less than fixing it later. Caltrain has a deplorable track record with future-proofing grade separation designs: the San Bruno grade separation and station, just recently completed in 2014, is already officially planned to be partially demolished for the high-speed rail project to straighten out a curve that could have been built correctly in the original design (reference HSR San Francisco - San Jose project DEIR Volume 3, Alternative A, Book A1 plan and profile drawings, sheet 7).

 

The same kinds of silly mistakes are now starting to be made in Redwood City, with an efficient layout to facilitate express overtakes and Dumbarton service being fumbled by oblivious consultants who excel at the road details and don't seem to appreciate the rail details. When they've got a hammer, the whole world looks like a thumb.

Risk and Opportunity in Redwood City

Lowe, a major real estate development firm, is preparing to redevelop Redwood City's Sequoia Station, an outdated strip mall adjacent to the Caltrain station, into a 12-acre mixed-use project with towers up to 17 stories tall.  If that is eye-opening to residents of Redwood City, consider that few people yet know that a greatly expanded Redwood City station is the keystone transfer node to enable the growth envisioned in Caltrain's business plan service vision. This new station will require slightly more land than the railroad already owns, and can only be located in Redwood City, the sweet spot that lies halfway between San Francisco and San Jose at the connection point to the Dumbarton rail corridor.

This creates a risk: if a commercial development project is allowed to proceed without respect to the future real estate needs of the railroad, then Caltrain will be constricted and unable to build the optimal infrastructure to support future growth.

Additional Land Needed For Caltrain

Caltrain and Samtrans have extensive land holdings at the Redwood City transit center. Still, just a bit more is needed to build a high-functioning piece of infrastructure, and be could traded for other parcels. Click to expand the map:

Land needed for future expanded station in Redwood City (shaded green)

Design Principles

The absolute worst way to build it.
Existence of this city rendering is
reason enough to be concerned.

To ensure that the Sequoia Station project becomes an exemplar transit-oriented development, rather than relegating Caltrain to the role of development-oriented transit, the rail agency and the developer should agree on some broad design principles.

• Think Big. Redwood City is one of the few stops on the peninsula rail corridor not surrounded by a sea of low-density single-family housing. Intensive land use and transportation must fit together to achieve a dynamic yet sustainable low-carbon future.
   
• Form follows function. No amount of architectural flourish or amenity can make up for a poor station design. Optimize for convenient access, easy transfers between trains and buses, short walks, direct and intuitive routes.
   
• Put the station at the center of the action, right over Broadway. Don't shove it to the north, out of the way of the development. The city rendering at right shows precisely what NOT to do.
   
• Configure the station as two island platforms to facilitate cross-platform transfers, without time-consuming vertical circulation or platform changes. The Caltrain business plan's staff-recommended service vision relies entirely on these Redwood City cross-platform transfers; every single train that pulls into Redwood City will make a timed transfer to another same-direction train docked at the opposite edge of the same platform. Denoting express tracks as 'F' for Fast and local tracks as 'S' for Slow, the optimal layout is FSSF with two islands, resulting in F-platform-SS-platform-F. Again, the city rendering shows precisely what NOT to do: passengers would not only have to change platforms, but also cross the tracks at grade.
   
• Elevate the train station to reconnect the street grid and make the railroad permeable to pedestrians, bikes, and other traffic. A busy four-track station is fundamentally incompatible with at-grade railroad crossings, and the only reasonable way to grade separate at this location is by elevating the entire station. Obstacles to pedestrian circulation such as the Jefferson Avenue underpass would be removed. Once again, the at-grade city rendering shows what NOT to do.
   
• Use four-track approaches from the north and the south. Cross-platform transfers are most efficient if trains do not have to arrive and depart sequentially using the same track, which adds about 3 minutes of delay. The best transfer is one where the two same-direction trains can arrive and depart simultaneously on their own separate tracks. Temporal separation is efficiently established by having the local train stop one station away from Redwood City (southbound at San Carlos or northbound at a new Fair Oaks station at Fifth Avenue) at each end of a new four-track segment that will ultimately measure four miles. In this arrangement, the express trains naturally gain on the local trains without a single passenger being delayed at Redwood City.
   
• Include turn-back tracks. Preserve room in the right of way north and south of the station for turn back pocket sidings, between the central slow tracks. Dumbarton rail corridor trains may not necessarily "interline" or continue on the peninsula rail corridor, so it's important to give them a convenient place to transfer and turn around without fouling other train traffic on the express tracks (hence FSSF arrangement). Same thing for a possible San Mateo local, which could serve the more densely spaced stops north of Redwood City.
   
• Don't be constrained by discrete city blocks. It could make sense to build structures or connect them over and across the tracks, more tightly knitting the station complex into surrounding mixed-use neighborhoods. This has some surmountable safety and liability implications, but buildings on top of busy stations are a common feature of successful cities around the world.
   
• Plan for long 400-meter platforms, not Caltrain's standard 700-foot platform length (again as seen in the city rendering of what NOT to do). While statewide high-speed rail plans currently do not include a stop in Redwood City, it is becoming enough of a destination and a regional transportation node that it makes sense to build a station large enough to future-proof it for service by long high-speed trains, regardless of what the California High-Speed Rail Authority might have to say about it.
   
• Think ahead about construction sequencing. Redwood City should be grade separated in one project from Whipple to Route 84, including the elevated station, taking advantage of Caltrain's land holdings to minimize the use of temporary tracks. A shoo-fly track would have to be built on Pennsylvania Avenue (within the railroad right of way) to make room for construction of the western two-track viaduct. Trains would begin using the elevated station while a second eastern two-track viaduct is constructed. Pennsylvania Avenue could re-open later, under the new four-track viaduct. Construction sequencing may drive how much extra land is needed for the railroad, so it's important to think it through up front.

If these design principles are respected, the re-development of Sequoia Station will present not a risk but an amazing opportunity to enhance Redwood City by realizing its full potential as the fulcrum of the Caltrain corridor and of a new regional express network reaching across the Dumbarton bridge and beyond.

Thinking Big in Redwood City

The architecture of Amsterdam Bijlmer
(photo by tataAnne) could represent
the future Redwood City station.

In a seamless transportation network that runs on a regular clockface schedule with timed, well-coordinated transfers, connecting nodes play a key role. Redwood City has natural potential as a connecting node, being located approximately at the midpoint of the peninsula rail corridor, serving as a logical transfer point between local and express trains, serving as the entry point to the peninsula from the future Dumbarton rail corridor, and being in of itself a significant destination with extensive connecting bus service and a willingness to grow.

With Redwood City currently renewing its interest in grade separations, it's important to think big and to re-imagine the station as a key node in the Bay Area's transportation network.

Start with a good timetable

Using our handy service pattern generator, let's see what we could do if we organized a blended system that made Redwood City a key transfer node. When you make a business plan, the first thing to be crystal clear about is: what is your product? In Caltrain's case, the timetable is the product, and all these stations and tracks should only be built as long as they contribute directly to delivering a quantifiably better timetable for the ordinary rider. Building a major new station in Redwood City isn't about trite superlatives like "Grand Central of the West," but simply about efficient and seamless coordination of timely and reliable ways to get from point A to point B.

Let's set some ground rules for our timetable:

• Caltrain expresses will operate every 10 minutes on a regular clockface schedule. A base 'takt' of 10 minutes reduces gracefully to 20 minutes or 30 minutes in the off-peak.
• In Silicon Valley, there will be no skip-stop service because the population and jobs are evenly sprawled. Every station in Silicon Valley needs to be served frequently, doing away with the ridership distortions induced by the Baby Bullet effect.
• In San Mateo county, where stop spacing is closer, slower local trains will operate every 20 minutes. These local trains will meet the express at Redwood City, before turning back north.
• Dumbarton service will operate every 20 minutes, meeting the express at Redwood City with little or no wait to transfer to trains on the peninsula corridor, before turning back towards the East Bay.
• Because the overall pattern repeats every 20 minutes, HSR will operate 3 trains per hour rather than the planned 4. Otherwise, there is a harmonic mismatch between the HSR frequency and the Caltrain frequency. 4 HSR trains per hour in a clockface timetable forces the base 'takt' to increase to 15 minutes, which is not desired.
• If we're going to make Redwood City a major node, it certainly rates HSR service, so we will create a new mid-peninsula stop for HSR.

This is the resulting timetable (see also additional data on service pattern), shown here for one hour in the southbound direction only (the northbound side is symmetrical). Colors denote the 10-minute Caltrain express, the San Mateo local, Dumbarton service, and HSR.

Notice the express arriving at Redwood City at 7:43 meets the Dumbarton train departing at 7:44, and the local arriving at Redwood City at 7:52 meets the next express at 7:53. Every ten minutes there is a cross-platform transfer, alternating between express-to-Dumbarton and local-to-express. Counting both directions, a cross-platform transfer occurs at Redwood City every five minutes!

Implicit in this timetable are a number of other capital improvements besides a new Redwood City station, such as overtake tracks in various locations along the corridor (highlighted in yellow in this view of the timetable... and while we're here, look how much less yellow is needed if HSR uses the Dumbarton corridor via Altamont Pass). It's important to remember that there is no formulation of the blended system that avoids the need for overtake tracks, unless one is willing to push slower trains into station sidings to sit for at least five minutes while a faster train catches up and pulls ahead. If you are a Caltrain rider, you should be wary of the cheapskates at the HSR authority who want to do this to your commute.

Deriving the functional requirements for the Redwood City node

To enable this timetable, we need the Redwood City station to have the following attributes:

1. Four platform tracks serving two 400-meter long island platforms to facilitate both northbound and southbound cross-platform transfers of very long, high-capacity trains.
    
2. Platforms centered on the best cross-town corridor, namely Broadway, for convenient access to and from local destinations on foot, by bike or scooter, by bus, or using the planned Broadway Streetcar.
    
3. A turnback track that enables certain Dumbarton corridor trains to originate and terminate in Redwood City, without fouling other train traffic, long enough for an EMU-8 train.
    
4. A turnback track that enables the San Mateo local to turn back in Redwood City, without fouling other train traffic, long enough for an EMU-8 train.
    
5. Elevated grade separation of all downtown Redwood City crossings, enabling free flow of pedestrians, bikes and vehicles under the rail corridor and including the re-connection of streets currently cut off by the existing configuration (e.g. Hopkins and James).
    
6. Bus facilities placed directly under the train platforms for seamless connections without the need for an umbrella. Same for an eventual Broadway Streetcar.
    
7. No mezzanine level. Mezzanines needlessly drive up the size and cost of stations, and impede and complicate vertical circulation. Street level can fulfill all the functions of a mezzanine, including ticket sales, wayfinding, waiting, retail, and dining.
    
8. The shortest and fastest possible vertical circulation (stairs, escalators, ramps, and elevators) using a U-shape viaduct cross section to avoid deep and vertical-space-wasting bridge structure. This helps with transferring quickly between the two island platforms, as would be needed for example to continue from the Dumbarton corridor south to Silicon Valley.

The footprint of such a station is not small. However, Redwood City has plentiful available railroad and transit district land, and the street level interface of such a station can be integrated into the city's street grid, opening up cross-corridor access and avoiding a wall effect. The aging Sequoia Station shopping center, with its wasteful surface parking, can be demolished and redeveloped to make room for an expanded station. Station parking can be moved underneath the approach structures, protected from the elements.

One possible station layout

An optimal station layout has four tracks, with the outer tracks for HSR and express commuter trains. The middle tracks are for commuter trains, and allow both northbound (Dumbarton) trains and southbound (San Mateo local) trains the opportunity to turn at Redwood City without impeding the flow of express traffic. The width of the structure is about 130 feet, as shown in the cross section below:

The northbound express track (Track 3) is tangent. The northbound island platform is 400 x 10 m. The center commuter tracks (Tracks 1 and 2) have curves that are not laid out in detail; this detail does not matter since any train that uses these tracks would slow and stop at Redwood City, using standard trackwork and turnouts. The southbound express track (Track 4) is the tricky one: it wows around the station, passing the southbound island platform on a 7500 m radius curve with approximately 1.5 inches of superelevation (not enough to matter for platform lateral tolerances). This track consists of a double reverse curve with six spiral transitions (tangent, spiral, curve, spiral, tangent, spiral, platform curve, spiral, tangent, spiral, curve, spiral, tangent). The curve is necessary to fit a pair of 400-meter island platforms (long enough to berth a double-length high-speed train) without bulldozing too much real estate.

Here is how this all fits (admittedly just barely) in downtown Redwood City:

The sacrificial victim is the Sequoia Station shopping center and associated surface parking crater, which can be redeveloped as part of the station complex with direct access from El Camino Real. Access for high-rise fire apparatus around the viaduct structure might also be a concern for the new condo buildings to the south, although this can be mitigated.

The station includes two pocket sidings to turn commuter trains. The siding south of the station can turn Caltrain locals at Redwood City, while the siding north of the station can turn Dumbarton service. Each siding is sized to store an eight-car EMU. Track center spacing is 15 feet throughout, and platform setback is 6 feet from track center. All viaducts are made from low-profile U-shaped sections that minimize the required height of the tracks and also double as sound walls, reducing the noise of up to 30 trains that would serve the station every peak hour.

Redwood City's slogan, "climate best by government test" would also become "transfer best" with timed, well-coordinated transfers to a variety of destinations. The impending start of designs for grade separations in Redwood City needs to factor in this future, and the city ought to think big.

Optimizing the Midline Overtake

The most important piece of infrastructure required for "blending" HSR with Caltrain on the peninsula rail corridor is an overtake facility, basically a several-mile long stretch of up to four tracks that will enable faster trains to overtake slower trains.  Caltrain studies have shown that the best performance (measured by robustness to cascading delays) can be achieved with a midline overtake  from San Mateo all the way through Redwood City.  Preliminary engineering and environmental clearance for this infrastructure is now resuming, with the recent award of a $36 million contract by the CHSRA to engineering firm HNTB.

The baseline configuration for this overtake is described in Caltrain's blended operations analysis, and assumes rebuilt stations at Hayward Park, Hillsdale, Belmont, San Carlos and Redwood City with four tracks and outside platforms in the tried and true style of the 1930s Pennsylvania Railroad. High-speed trains would use the center pair of tracks to overtake slower trains on the outside pair of tracks, as shown below (click figure to enlarge):

For comparison, the figure also shows a better solution that ensures the highest level of punctuality for all trains using the corridor.  This optimized overtake configuration differs from the baseline configuration as follows:

• The slow trains run in the middle, so that disruptions to local commuter service (for example, when an incident blocks a track for hours) do not disrupt high-speed service when commuter trains are re-routed around the incident location.  This track configuration is known as Fast-Slow-Slow-Fast (FSSF) as opposed to the traditional SFFS.  Real world examples of FSSF can be seen in train cab videos from Sweden and Australia.
   
• All commuter stations are built with central island platforms.  This allows commuter trains to use either platform face without confusing passengers, and requires only one set of station amenities (shelters, elevators, escalators, stairs, ticket vending machines, PA systems, train arrival screens, lighting, benches, etc.) because there is only one platform.
   
• A major new interchange station at Redwood City, with four platform tracks and additional train storage sidings.  This station (described below) would serve as a transfer point for HSR, Caltrain and future Dumbarton trains, as well as non-rail transportation modes.
   
• A carefully planned future-proofed high-speed rail junction where the Dumbarton rail corridor meets the peninsula rail corridor, preparing for the inevitable arrival of passenger rail service across the Bay.

Here's how it would ideally play out.

Short Term: the San Mateo Grade Separation

Preliminary rendering of new
Hillsdale station with island platform

The next step in the decadal process of grade separating the peninsula rail corridor will soon begin in San Mateo.  A new $180 million grade separation project is in the final stages of planning for 25th Avenue (currently a grade crossing) as well as 28th and 31st Avenues (currently not connected).  Concurrently with this project, the busy Hillsdale station will be moved a bit north of its current location and turned into an island platform.

This project is caught in an interesting political bind.  There is on one hand a rush to complete it by 2019 before Caltrain's electrification project, to minimize disruptions to Caltrain service.  On the other hand, due to its strategic location, this project will form a key building block of the blended system with HSR, which still needs to be environmentally cleared.  It is a near certainty that this portion of the corridor will require four tracks to enable trains to overtake each other, but any attempt to design and build it as such is likely to run afoul of HSR opponents who will accuse the CHSRA of advancing their project through CEQA piece-mealing.

The southern San Mateo grade separation design will have to be very carefully considered to preserve the ability to add two additional tracks with as little disruption as possible.  Road underpass profiles and bridge abutments should be designed for four tracks, as should the elevated structure that will support the tracks.

The choice of an island platform configuration for the new Hillsdale station is either a sneaky way to build a wide four-track embankment in preparation for yet another new station with SFFS outside platforms, or is an excellent choice for FSSF because it allows future tracks to be added without rebuilding the station for a second time.  One hopes the station access (stairs, ramps, etc.) will be designed to allow the platform height to be raised easily from 8" to 50".  An intelligently designed San Mateo grade separation would atone for the terrible failures of the San Bruno grade separation, designed with great hostility towards higher speeds or additional tracks.

Medium Term: Redwood City HSR Station

Amsterdam Bijlmer (photo by tataAnne)
could just as well be the future
Redwood City train station.

While the CHSRA's plans for a mid-peninsula stop have been shrouded with ambiguity for several years, Redwood City stands out as a more optimal location for a new HSR station than Palo Alto or Mountain View, the other two locations in the running.  Unlike its neighbors to the south, Redwood City favors strong urban growth, has a large amount of railroad land available, and is reasonably well-connected to the existing road and transit network.  Redeveloping the antiquated but popular Sequoia Station shopping center would enable the construction of an elevated four-track station with plenty of capacity to support not just HSR but also Caltrain cross-platform connections and future Dumbarton service.

The station complex would feature two shared (HSR or Caltrain) 400-meter island platforms centered between Broadway and Brewster, easily accessible from both streets.  Bus connections would be conveniently located under the station. To the north of the platforms, a pocket turnback track would allow Dumbarton trains to reverse without fouling other traffic.  Similarly, to the south of the platforms, another pocket turnback track would allow southbound Caltrain locals to terminate in Redwood City before turning northwards again to serve the densely-spaced stations of San Mateo County, allowing Caltrain to serve more passengers with fewer trains and crews.  Thanks to the FSSF configuration, all this to-and-fro by commuter trains would stay well out of the way of HSR.

This would be a large train station and quite a tight fit (if you're curious about exactly how large and how tight, download this KML file into Google Earth to view the station footprint and track layout).  It would be a big change for Redwood City, but with a huge payoff: the tracks would no longer form a barrier through town, and the Sequoia Station shopping center would be merged with the station to form a gateway and a destination in its own right that is connected to downtown.  HSR service could make the city a very desirable location for business.  The new station could become the centerpiece of the ambitious revitalization strategy described in Redwood City's downtown precise plan.  But this idea is not without pitfalls, as the size of the station could be compared to plonking a couple of Nimitz-class aircraft carriers in the middle of town.  To use the tired slogan, it needs to be done right.

Medium Term: a New Fair Oaks Station

Approximate location of new Fair Oaks
station island platform, view to northeast.
Overtake would extend just beyond
platform to the right (south).

The key to reliable overtaking on a multiple-track railroad is to ensure that the average speed of the slower train being overtaken is sufficiently slower than the average speed of the faster overtaking train.  One of the ways of ensuring a good speed differential is to have the slower train make station stops that the faster train doesn't; each station stop is worth about 2.5 minutes.  Therefore, locating stations on the four-track overtake section is helpful.

This brings us to a lemon of a station immediately south of the midline overtake: Atherton.  Located in an area of very sparse population and jobs density, Atherton should be permanently closed.  This closure would come not only as a show of appreciation commensurate with the town's support of Caltrain modernization, but especially because census data shows clearly that Atherton is precisely where you would never place a train station.

To replace Atherton, a new Fair Oaks station should be built just 0.6 miles to the north, at the 5th Avenue grade separation.  The overtake section would be extended a bit southwards, just beyond the station, enabling locals to be passed while stopped at the central island platform that can be accessed from either side of 5th Avenue.  The new Fair Oaks stop would be equidistant from Redwood City and Menlo Park, and located in an area with very high population density that could support thriving ridership, in contrast to Atherton.

Longer Term: a Seamless Dumbarton Connection

Dumbarton rail has been an uncertain prospect for decades, with some political backing but insufficient funding.  While it may take another few decades for the money and the will to finally materialize, large concentrations of employment and the need for additional transbay corridor capacity make some form of passenger rail service inevitable.  The Dumbarton corridor also happens to be ideally suited for high-speed rail.

The key node is Dumbarton Junction, which should be reconfigured in such a way that trains can enter and leave the peninsula rail corridor swiftly and seamlessly.  This will likely involve a flyover track, enabling southbound trains to enter the Dumbarton corridor without crossing (and therefore blocking) any of the northbound tracks.  To minimize the altitude of the flyover, the Rte 84 / Woodside Road overpass would be turned into an underpass.  As for the Redwood City station, the fit would be quite tight with a 90-foot corridor width where the flyover track begins.

While the flyover may seem like an expensive solution to a problem we don't yet have, planning for it now (if not actually building it) will save money in the long run when passenger rail service grows.

Design Values

No matter how the midline overtake is ultimately configured, it must reflect design values that are clearly articulated.  One of these values should be compatibility between Caltrain and HSR.  It's not enough to talk about the "blended system" without actually taking the steps to make the two systems seamlessly interoperable, allowing any train to use any track to serve any platform.  This means no tracks can be dedicated to one operator at the exclusion of another.  Everything must be shared, including the platforms at the new mid-peninsula station.  This sharing contributes to another important value, robustness to service disruptions.  The fast-slow-slow-fast track layout is the key to ensuring that a commuter train delayed in Belmont won't create a statewide domino effect that eventually makes a train late in Los Angeles.  A third important value is future-proofing.  Infrastructure like the midline overtake will define what is possible (and not) for generations to come.  It would be short-sighted not to plan for a fast and seamless connection to the Dumbarton corridor, even if its future use isn't well-defined today.

The midline overtake is the key to an effective blended system.  When evaluating its design, ask yourself: is it compatible?  Is it robust?  Is it future-proof?

Census Driven Service Planning

The diagram at right shows where people live and work along the entire length of the rail corridor from San Francisco to Gilroy, as extracted from government census population and jobs data sets.  The diagram is also available as a PDF.

Implications for Rail Service Patterns

By simple observation of the features of the census population and job distributions along the peninsula corridor, it is possible to infer the desirable features of train service patterns that will maximize commute ridership.

1. Transbay has more than 100,000 jobs within a half-mile radius (more than every other station in the system combined). The concentration of jobs near San Francisco's Transbay Transit Center cannot be understated. This station absolutely must be served by each and every train, and it would be highly counter-productive to terminate any train at 4th and King.
    
2. Silicon Valley shows up in the jobs distribution as a broad hump, mostly homogeneous and stretching from Palo Alto to San Jose.  To serve this rich but diffuse commute market, all trains should make every stop in Santa Clara County.  There should never be any skip-stop service here, and the wider spacing of stops (relative to San Mateo County) will result in only minor trip time penalties.
    
3. San Mateo County has numerous stops, spaced more closely together and with middling jobs and population density.  To enable faster service to and from San Francisco and Silicon Valley, it makes the most sense in this portion of the corridor to operate skip-stop express service alongside local service.
    
4. South San Jose, while south of Silicon Valley, has a massive and untapped residential market that can serve as origin to jobs further north.  Tamien currently functions as a slow and infrequent addendum to the peninsula service, but should be sped up and extended to Blossom Hill.
    
5. Oakdale in San Francisco opens up a new residential market for Caltrain.  The distribution of people nearby is even denser than at 22nd Street.
    
6. The Gilroy extension doesn't make much sense.  There are so few jobs and people here that Caltrain (as primarily a commuter service) should not run to this area.  Serving Morgan Hill and Gilroy is best left for a long-distance operator such as Amtrak California.

Putting all this together, what would a service pattern look like that is tailored to the census distributions, to maximize commuter ridership?  First, it would not look like today's Baby Bullet, which severely under-serves numerous stops.  It would also look very different from Caltrain's latest planning fad, the "peak-period skip-stop zone express," used as the basis for all operational simulations in the blended service analyses published to date.  It would look like this, with distances drawn to scale:

• The Silicon Valley express links the major employment centers of San Francisco and Silicon Valley, highlighted in orange, providing a faster and better alternative to fleets of white luxury buses stuck in traffic on US 101.  It would run every 15 minutes.
   
• The San Mateo local serves all the minor stops throughout San Mateo County, terminating and originating across the platform from the Silicon Valley express at Redwood City.  This provides fast and penalty-free transfers between Silicon Valley and cities all along the peninsula.  The local turns back in Redwood City, minimizing crew and fleet requirements while still providing service every 30 minutes.
   
• Stops in San Francisco and San Jose that have very large residential markets are served in the peak commute direction only.

This service pattern is also well-suited to future blended HSR service: a southbound high-speed train and a closely-following Silicon Valley Express can overtake and catch up (respectively) with a San Mateo local by using a four-track mid-line overtake facility constructed from San Mateo to Redwood City.  Because the local turns back at Redwood City, it does not impede traffic in Santa Clara County.

The time has come to fundamentally rethink peninsula rail service patterns.  Caltrain's "peak-period skip-stop zone express" is almost certainly not the best solution for meeting future demand; a much wider range of options must be considered.

Grade Separation: The Decadal View

For the last few years of debate around the issue of high-speed rail, grade separating the peninsula rail corridor was often cast as an all-or-nothing proposition.  This extremist view clouded two important facts: first, the corridor is already mostly grade-separated (in 2013, only 40 road crossings out of 104 between San Francisco and San Jose will remain at grade); and second, grade separation is a slow and inexorable process that takes place over many decades.

If we assume the next several decades will be like the last several decades, we can take an educated guess about how and in what order grade separations will be built.  The criteria for prioritizing each project could be:

• creating long, uninterrupted stretches of grade separated right of way to enable higher train speeds without compromising safety
• creating a four-track mid-line overtake facility to increase the capacity of the corridor, to support initial HSR service
• separating crossings that rank highest in the CPUC's Section 190 Grade Separation Priority List
• delaying the most expensive and politically costly projects until last

Phase I is simply the completion of the San Bruno grade separation in 2013.  The San Mateo / San Bruno grade crossing being replaced was once rated #7 statewide on the CPUC's priority list.

Phase I: San Bruno Grade Separation

Phase II consists of four projects in San Mateo County, opening up two long stretches free of crossings by the early 2020s, including 14.8 miles free of crossings north of Burlingame, and 6.5 miles south of San Mateo.  This enables the future construction of the "short" mid-line overtake envisioned in Caltrain's corridor capacity analysis, and leaves only a few dense clusters of crossings within San Mateo County.  The new grade separations, in order of priority, are:

1. 25th Ave in San Mateo, the only grade crossing that remains between San Mateo and Redwood City.  Along with new grade separations already planned at 28th and 31st, this project enables the future 4-track mid-line overtake.
2. Broadway in Burlingame, an extremely congested crossing that has been slated for grade separation since the 1970s.  It rates #11 statewide on the latest CPUC priority list.
3. Linden Ave in South San Francisco, originally planned as part of the San Bruno project, but dropped from the final design in 2007.  Grade-separation at Linden is accompanied by the closure of Scott St, which becomes a pedestrian tunnel.
4. Center Street in Millbrae, a grade separation that will require a U-shaped elevated ramp due to the nearby BART subway tunnel box.  Such are the consequences of bad planning.

Each of these projects is independent and can be negotiated on a case-by-case basis with the four affected cities.  Starting in San Mateo County allows at least another decade for the Pacheco vs. Altamont debate to run its due course, legally and politically; these four projects are useful either way.

Phase II: San Mateo County Grade Separations

Phase III occurs mostly in Santa Clara County, creating a new stretch free of grade crossings from the southern half of Palo Alto all the way to San Jose in the late 2020s, assuming the routing of HSR over Pacheco survives as currently planned.  The last two grade crossings in San Francisco are also eliminated as part of the downtown extension project.  This phase includes the following six discrete projects:

1. Mary Ave in Sunnyvale, the corridor's busiest grade crossing in this county, with more than 25,000 daily vehicles
2. Sunnyvale Ave
3. Rengstorff in Mountain View, with about 18,000 daily vehicles
4. Castro in Mountain View, with about 9,000 daily vehicles
5. Charleston and East Meadow in Palo Alto, with a combined ~30,000 daily vehicles plus numerous pedestrians and bicyclists
6. 16th and Common in San Francisco, as part of the DTX project

Together, these six projects create a new 16-mile stretch of track that is entirely free of grade crossings.  The corridor is now left with just three dense clusters of grade crossings, in San Mateo / Burlingame, Redwood City, and PAMPA (Palo Alto - Menlo Park - Atherton), highlighted in orange in the figure below.  Note that these three dense clusters contain 27 crossings, and that to get this far, only 12 existing crossings were newly separated.

Phase III: Santa Clara County Grade Separations

Phase IV is the Great Redwood City Grade Separation.  This project, potentially for the early 2030s, would prolong the four-track mid-line overtake by three miles, by removing six grade crossings in downtown Redwood City.  Removing this cluster first makes sense from the standpoint of increased corridor capacity, the lowest number of new structures, the short mileage, and the entire project being politically simplified by virtue of its containment within Redwood City limits.

Phase V is the Great San Mateo / Burlingame Grade Separation.   This is a tougher project because it involves some of the most highly constricted portions of the corridor.  It also involves political and technical coordination between two neighboring cities, adding an additional challenge.  The sheer quantity of crossings (13 grade crossings + 4 obsolete grade separations within 2.4 miles) is also a complicating factor.

Phase VI is the Great PAMPA Grade Separation.  This project is left for last because it lies in the most expensive real estate on the corridor, involves coordination between three different cities, and is liable to cause the fiercest political and legal backlash anywhere on the peninsula.  Delaying it until last, perhaps into the late 2030s, allows the customarily long planning process to run its course without undue haste in all three affected communities.

We didn't arrive at today's state of grade separation (more than half) overnight.  It resulted from a slow and steady process that began in earnest in the 1940s.  The future is likely to be similar, and the peninsula rail corridor can reach a far improved state by separating just 12 more crossings over the next couple of decades, as described in Phases II and III.  This dozen should be prioritized for construction, before any of the crossings in the remaining dense clusters are touched.