Baby Bullets and Single Track Corridors
Let me be more precise, here. The 86 train per hour schedule has 5 trains per hour at peak, with "Baby Bullets", Limited Stop Express trains (they are not really Bullet trains), which shave the best trip time substantially. An early hours local takes 5:05 to 6:36 to get San Jose to SF 4th and King, 21 stops in 1hr 31min. A semi-express (a local collector in the south then express in the north) takes 6:57-8:19, 13 stops in 1hr 22min. An Express takes 7:50-8:57, 11 stops in 1hr 7min.
And a Baby Bullet takes 7:45-8:42, 7 stops in 57min.
In the new schedule, the Baby Bullet is gone. There isn't additional other services to take its place ~ its just scrapped. And according to Clem's metric, the schedule improves.
Are People Riding "the train" or a particular train?
Now, if people are riding a particular train, what matters is whether it runs on time and how fast the trip takes. Here, what matters is either the earliest you can leave or the latest you can arrive, and the transit time of the train with the best fit. If express trains are tuned for dominant travel tasks, average trip time underestimates the impact of express trip time, hence the extra weight in Clem's formula.
Also, some trips are flexible, and travelers on these trips will gravitate to the express trips, so "availability" of Express trips also weighs greater than the average in that way.
Which means, add Limited Express services to a mix of Local, Semi-Express and Express services, and "everything else equal", the score should go up ~ faster average trip time, and faster express trip time.
So something in "everything else" just aint equal. And its got to be in that wait time.
Consider if you cycle to the train station ~ you have a flat tire, or more happily you encounter someone you know and stop to chat ~ and you miss your train. If the wait is 10min, well, no big deal. If the wait is 20min, that's a bit of a drag. If the wait is 50min (this was typical for Lake Macquarie in NSW, with two trains per hour, but the local designed to connect to the express at the southern end rather than to alternate with express trains) ... well, that time drags on forever.
And just as with the fastest trip time, the maximum gap has a bigger impact than a simple average can capture, since there is always someone who's trip given the timetable is facing the maximum gap rather than the average gap.
The problem is the flip side of the benefit of a Ltd. Express. If all the trains are using the same track, then the local that takes 34 minutes more than the Ltd. Express can't run to the locals-only platforms twice an hour at even half hours intervals. That is, if the Ltd. Express leaves three minutes before one of the local trains, that's twenty seven minutes before the preceding local, and so somewhere in south San Francisco the Ltd. Express is dawdling through at the same speed as the local in front.
Add in one or more Express schedules serving the mid-tier stations that the Ltd. Express skips, and there is no escaping big gaps in front of the Ltd. Express to give it room to run faster than the trains it is chasing.
Dropping the Baby Bullets allows for a far more even scheduling of the remaining services, and that is where the net improvement comes from.
The Mid-Peninsula Overtake And Fixing the Problem
Now, you want your expresses to be faster than your locals, but if they are too much faster, you mess up the scheduling of other trains in the system. And an effective local transport use of the Caltrain corridor will require more trains per hour, which would seem to make the problem worse.
The solution is straightforward: an overtake. A Clem argues:
Contestant #3: a plain vanilla takt-timetable featuring only 6 trains per hour in each direction at peak times. Four of those trains are all-stops locals (running at regular 15-minute intervals, with a 93-minute run from Transbay to Tamien) and two of them are expresses, which take advantage of the four-track peninsula rail corridor to overtake locals. One of those overtakes occurs at the middle of the line at the Redwood City station, where the local and the express stop simultaneously on opposite sides of the same platform and exchange passengers--at this stop only, we make an exception to the 3-minute transfer rule. This cross-platform transfer extends the benefits of express service to a much wider selection of O&D pairs than today's Baby Bullet.
When benchmarked against the then-90-train schedule as 100, that scored 142, when the ten train per hour schedule in the 2025 Alternatives Analysis only scored 147. That is roughly a 96% benefit at a roughly 60% operating cost, so an operating benefit/cost ratio improving by around 60%.
And as opposed to a complex stop-skipper schedule, there is a side-effect benefit of the steady, regular schedule of locals and expresses: support for connecting bus service. A steady station departure at locals stations every 15 minutes means that whatever the bus schedules happen to be that serve that schedule, the only really awkward time to arrive is just as the train does ~ only shifting the bus schedule either forward or back five minutes will result in a comfortable arrival, with slack for late running buses but without excessive waits at the station.
Whether the bus is on an hourly, half hourly, twenty minute, or quarter hourly frequency, the steady schedule of the train service means that passengers can just learn, "this bus connects with this train at this station", without having to consult bus and train timetables to work out when it hits and when it misses.
What About the HSR
Note that this assumes that the High Speed Rail tracks can be used for Express Overtakes. How safe is that assumption?
Well, first there is capacity. The 220mph component of the California HSR system is required, by law, to support 5 minute headways. That says that the maximum number of trains that can be fed off the 220mph HSR corridor in a fifteen minute period is 3 trains.
Headway is determined by lots of things, but safe stopping distance is a real important one. Positive Train Control says that the system can bring a train to a halt in response to not having safe passage ahead. And any train behind it also has to be brought to a halt in time to avoid rear-ending it.
If the HSR tracks through the Caltrain Corridor are Regional HSR track that can support speeds of 125mph, then it would be quite reasonable to design it for three minute headways. Three minute headways mean that five trains can pass through the track in a fifteen minute period.
If the 220mph Express HSR corridor can only feed three HSR trains in per fifteen minutes, and the Regional HSR tracks can handle five trains per fifteen minutes, then in terms of system capacity, using the Regional HSR Caltrain tracks for Express bypass seems perfectly reasonable.
What about actually getting from the local to the Express tracks and back? The most convenient configuration has the local tracks in the middle, serving island platforms, with the express tracks on the outside (if you think its the other way around, you are thinking car expressways with slow lanes needing access to on-ramps and off-ramps). The second most convenient configuration is express through the middle and local tracks on the outside, with side platforms except for the islands that the HSR stop at.
So assume that its the least convenient, the express tracks as a pair on one side, and the local tracks as a pair on the other.
Even here, with advance planning, its reasonable straightforward to provide access. The key is to take advantage of the fact that the local tracks are shared with freight trains at night, with a normal maximum 1% gradient, while Express HSR and Express Electric Passenger trains can comfortably handle 2.5% gradients. For the connection to the local track, I will allow a gradient of 3%.
Now, consider a rail overpass that is going to clear 20 feet. Assume that an overpass over the rail has to clear 30 feet.
The local track at grade is going to have to start rising 2,000 feet back. At the start of that, the Express track can split, with a connector track between the two running tracks. The through tracks can rise at a 2.5% grade while the connector track dives at a 2.5% grade. That is a 5% net gradient, which means the 30 foot difference is covered in 600 feet.
At this point, the express through track is 15ft above grade, the connector 15ft. below grade, and the local track is 6ft. above grade. The connector can run underneath the through tracks, but still needs 9 more feet of clearance to get under the local track. Diving at 3% with the local rising at 1% is a 4% net gradient, which can finish the 9ft in 225ft.
Now, the connector can run underneath the local tracks, which can be split to allow the connector to rise from underneath. For the remaining 1,175 ft. of the rise of the local, the connector is rising at 3%, the local rising at 1%, for a net gradient of 2%. That brings the connector up 23.5ft closer to the level of the local track, with 7.5ft to cover. Easing the gradient to 2.5%, it can cover that final 7.5ft vertical gap in 300ft.
Rather than a run of 2,000ft, this connector taking advantage of the climb of the local track requires a run of 2,300ft or so. Two well-placed connectors like this, at opposite ends of a stretch of corridor between two express stations, and you have an Express overtake for one direction of travel.
Actually, in some cases a pair of overtakes like this could work for both directions of travel if the opposite directions are well spaced in time, but in the notional timetable Clem has put up, the northbound overtake is between Millbrae and 22nd Street to its north, and the overtake for southbound trains would be between Millbrae and Hillsdale to its south.
I'd stress here that it is quite clear that running the Caltrain and the Regional HSR rail side by side ~ whether:
- "Fast | Slow | Slow | Fast", or
- "Slow | Fast | Fast | Slow",
... would be far more flexible and far cheaper. The overtakes have to be placed at locations where express trains in opposite directions will be overtaking in different sections of the hour. That is helped by the proposal to have one overtake be a platform overtake, with one station expressly designed to swap passengers between express and locals going the same way, with the local leading in and the express trailing, then express leading out and the local trailing,
However, even if the track are laid out
- "Fast | Fast | Slow | Slow"
... its possible
to design in one express overtake at platform at Redwood City, and one overtake closer to San Francisco, after leaving Millbrae north or south, and support a clockface schedule with two express services per hour, without imposing any substantial constraint on the primary use of the Express corridor by the California HSR services.
Caltrain Express, Local and Preliminary HSR Services
One final point here. Many HSR corridors around the world have had their first services brought into operation before the entire first stage corridor is in operation. This allows the system to start building patronage before the full corridor is completed, which can substantially boost the operating revenues in the early years once the full corridor is completed. It also means getting earlier benefit for the capital investment, which can only improve the benefit/cost of the project.
The same could be done for California HSR. If, for example, the Express HSR corridor is completed from San Jose to Palmdale, and the existing Metrolink corridor from Palmdale to Union Station upgraded to allow the service to continue at conventional rail speed to Union Station ~ then as far as the Caltrain Corridor would be concerned, the Express HSR operating on the Caltrain corridor would be equivalent to a faster Express.
And since the Express trains in Clem's schedule are designed to permit two Express trains per hour operate a regular schedule alongside four local trains per hour, it follows that two Express HSR trains per hour could slot in as a third and fourth Express.
In this system, a natural progression would to first build what will be new local track when the corridor is shared by four tracks, including the express tracks that are used as Express overtakes. Careful project planning should allow the Caltrain corridor to continue to be used as new track is laid on the "slow" side of the alignment.
Then electrifying the Caltrain corridor, including the Express overtake, would allow a preliminary service of the California HSR to run through to San Francisco.
Then construction can proceed on completing the Regional HSR components of the track, in parallel with work on completing the Express HSR corridor from Palmdale to LA-Union Station. When both are completed, the upgrade in HSR service frequency can commence.
Midnight Oil ~ Truganini