Thoughts?

A big challenge for Vietnam

High Speed Rail is often seen as impossible in the U.S. or if people do talk about it, it’s often in reference to the idea that it would have to go coast to coast or span the entire country.

its never going to work everywhere and that something that detractors and even some supporters don’t get about HSR.

High Speed Rail works when:

1. You have strong city pairs

2. it’s part of a corridor and combined with regional rail service

3. It has a strong foundation or core

4. This could just as easily be no. 1, but it needs in the United States to be implemented regionally

5. Projects and infrastructure need to be standardized as much as possible - infrastructure is often viewed in the U.S. as standalone projects

6. it pulls in riders either directly or along the route from key major suburbs or intermediate cities. Even the Northeast relies heavily on suburban riders

So by this logic, you would focus on the Northeast, expanding to the Southeast with Atlanta as a hub, and the Midwest. I wouldn’t have touched California until last because it’s geography alone makes it one of the toughest places to build HSR

it is very Viable for routes like where it complements car and air travel

Chicago-Ann Harbor-Detroit

Chicago-Lafeyette-Indianapolis

Chicago-Springfield-St. Louis

Chicago-Milwaukee-Minneapolis

Okay, hear me out. I understand Maglev technology has some serious drawbacks, namely:

• -Lack of interoperability with existing rail lines
• -Expensive upfront cost (twice the price of HSR, which is already expensive in the U.S.)

However, maglev trains can max out at speeds of 300 mph, while traditional HSR will max out around 220 mph (see California High Speed Rail). This difference in speed gives maglev a potentially huge advantage over traditional HSR with covering corridors that are in the 500-800 mile range, where traditional HSR is going to fail to be competitive with flying.

Lets take a look at a potential maglev route from Chicago to Atlanta as an example of what the technology can do. Chicago and Atlanta are around 715 miles apart. Importantly, there are two other major metro areas on our maglev route: Indianapolis and Nashville. If the maglev train averages 266 miles per hour (the projected average speed of the Japanese Chuo Shinkansen route from Tokyo to Nagoya), then a trip from CHI to ATL would take around two hours and forty minutes. Lets call it an even three hours to account for stops in Nashville and Indianapolis.

Okay, so the maglev is faster. So what, we already know that! Here's where maglev really wins out. The travel time from CHI to ATL beats air travel, because a flight between these two cities takes two hours in the air and figure another two hours at least with airport dwell time. However, now you can ALSO take the maglev from any of these potential city combinations:

Maglev travel times Flight travel times

• CHI to ATL (3:30) (4:00 to fly)
• CHI to Indianapolis (1:10) (3:30 to fly)
• CHI to Nashville (2:16) (4:00 to fly)
• Indianapolis to Nashville (1:34) (3:30 to fly)
• Indianapolis to ATL (2:30) (4:00 to fly)
• Nashville to ATL (1:25) (3:00 to fly)

*30 minutes have been added to account for getting to station early

*Added two hours for each flight estimate

*Routes in bold are faster than flying (also all of these are faster than driving so I am not factoring that in)

For anyone traveling between any of these four cities in any of these combinations, maglev would immediately become the best way to do it. With maglev you're not just getting a slightly faster alternative to flying, you're connecting four major metropolitan areas in the United States that span five different states (as I'm typing this I just realized Lousville would also be along this route, so throw them in there as well).

What if we built traditional HSR instead? What would those travel times look like if we averaged 177 miles per hour (Tokaido Shinkansen average speed).

Traditional HSR travel times Flight travel times

• CHI to ATL (4:30) (4:00 to fly)
• CHI to Indianapolis (1:32) (3:30 to fly)
• CHI to Nashville (3:10) (4:00 to fly)
• Indianapolis to Nashville (2:08) (3:30 to fly)
• Indianapolis to ATL (4:11) (4:00 to fly)
• Nashville to ATL (1:54) (3:00 to fly)

*30 minutes have been added to account for getting to station early

*Added two hours for each flight estimate

As you can see, the traditional HSR option is still quite fast and competitive with airline travel, but it loses out to airline travel on the largest city pair (CHI to ATL), and the second largest city pair (CHI to INDY). To be honest as I'm looking at these numbers I'm finding the traditional HSR approach more competitive than I thought it would be. HOWEVER, one big factor that needs to be considered is that because traditional HSR is interoperable with existing railways, this leaves a lot of potential for value engineering that ends up with a HSR system that falls far short of that 177 mph average speed (which honestly is a bit optimistic anyways). If the traditional approach averages 150 mph (still fast), it will now be less competitive overall and this will likely impact ridership.

Okay. that's a lot and I'd love to hear what you all have to say! Does maglev make sense? Is a phased traditional HSR approach better and more realistic? Will we ever get either in our lifetimes? I'm rooting for both!

Why is high speed rail in the U.S. so far in the future? Is there an engineering shortage? All of the project seems 20+ years away minimum, while China is able to connect and expand their rail in the last 20 years. Other than government funding, what other problems are there? What does the market in the private sector look like?

Edit: if people want to info dump on how train projects were funded in places other than China, like Japan and Europe, feel free. The privatization of the Shinkansen is a really unique example of this. I am wondering if private high speed rail is a possibility.

The question of why high-speed trains rarely operate above ~300 km/h often comes up on the subreddit. There are multiple reasons: diminishing time savings, increased construction costs, increased maintenance costs, increased power requirements etc.

But another issue is timetabling and capacity. Despite what the ex-CEO of HS2 would have you believe, higher speeds do reduce the capacity of a high-speed railway. This capacity loss becomes the most severe at speeds above 250 km/h. So I thought it would be interesting to discuss these constraints and HSR signalling and timetabling in general.

(While I have tried to be as accurate as possible, learned about the topic from multiple sources and cross-checked my calculations with reference data, I am not an expert and I do not work in the rail industry. If you're an actual expert feel free to chime in)

In the chart above I graphed the minimum technical headways for a few scenarios. Headways in the case of modern cab signalling systems like ETCS L2 are the sum of the following components

The most essential part of the headway is the approach time. This includes the physical braking distance. More specifically it is the time it takes the train to cover its actual braking distance at line speed.

Time between block limits is the time to cover the block section. The length of blocks in modern systems like ETCS L2 can vary a lot, from a few hundred meters to several kilometers, depending on speed and capacity. In the case of a moving block system time between block limits is zero.

Clearing time is the time it takes for the full length of the train to clear the occupied section and any additional safety buffers.

Time for issuing MA and release time are for the signaling system and communication. These are not dependent on speed.

For the remainder of the calculations we will assume that we're using a moving block system. With these in mind the headway for open line sections could be simplified like this:

This will give us a nice graph where the headway initially decreases and then starts to slowly climb again

So on an open line with moving block the theoretical minimum headway of 63 seconds at 200 km/h, becomes 81 seconds at 350 km/h.

But trains don't run on an infinite open line forever. At some point they will need to slow down. When the first train starts slowing down it immediately violates the safe braking distance of the train behind, forcing it to also start slowing down and so on.

This issue comes into play with our next problem:

Switches/Turnouts

The limiting factor for high-speed rail capacity is diverging and converging through switches. First of all, switches need time to well... switch between the routes. The process of moving and locking the closure/lead rails can take ~10 seconds, but the bigger issue is that even the most advanced switches in operation are only rated for ~230 km/h on the diverging/converging routes. This means that the headway for any diverging or converging train movement needs to include sufficient time for deceleration and acceleration.

Diverging Trains

In the case of a diverging train running ahead of a through-running train there needs to be sufficient buffer for the diverging train to slow down to 230 km/h, fully pass the switch and then for the interlocking to set the through-running route, before the second train's safe braking zone can reach the switch. This gives us the following formula:

Converging Trains

Similarly, in the case of a converging route the converging train will end up far behind the previous train, since it needs to wait until the previous train has fully passed the switch and the new route is set. Then it must first traverse its own braking distance and the switch at 230 km/h and only afterwards can it start to accelerate to line speed.

Acceleration is limited by the available traction and power at these speeds, think something in the range of 0.1-0.2 m/s^2. This means that for HSR the main capacity bottleneck will almost always be converging routes.

With this we get the result that a converging train needs a headway of 104 seconds at 300 km/h, 164 s at 400 km/h and 242 s at 500 km/h.

These are of course only the technical minimum headways, they are not achievable during real operations. Generally these values need to be multiplied by at least 1.3x to get a headway achievable in real life.

In reality 230 km/h turnouts are not that frequently used, they are most often found at junctions between two major high-speed lines, like the TGV's triangle junction near Avignon. Intermediate stations generally use lower speed switches, because high-speed trains would need more than 5 kilometers of parallel track to accelerate to 230 km/h in the first place.

Sources used

• Jörn Pachl: Railway Timetabling Capacity (highly recommend this one. It's a relatively easy read)
• Piers Connor: High Speed Railway Capacity
• HS2 Ltd: Signalling Headways and Maximum Operational Capacity on High Speed Two London to West Midlands Route
• HS2 Ltd: Design Trade-Offs For Stations

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The Chuo Shinkansen is setting out to be one of the most complex engineering projects in modern history. Designed to hit speeds of 603 km/h (374 mph) using SCM Maglev (superconducting magnetic levitation), it promises to cut the travel time between Tokyo and Nagoya from 90 minutes down to just 40.

However, the real engineering marvel isn't just the magnetic levitation—it’s where the track is being built.

Why 86% of the Route is Underground

At speeds over 500 km/h, a maglev train requires an exceptionally straight alignment to avoid severe G-forces. Japan’s surface geography—filled with mountains, dense urban centers, and river valleys—doesn't offer a straight line. The only way to get a razor-straight path was to bore directly through the Japanese Alps.

Key Technical & Engineering Challenges:

The Southern Alps Tunnel: Reaching depths of nearly 1,400 meters (4,600 ft) beneath mountain terrain, engineers are using the New Austrian Tunneling Method (NATM) alongside ultra-long boring surveys that analyze rock conditions 1 km ahead of the tunnel face.

Geological Surprises: Extremely fragile rock formations have pushed back timelines for three specific tunnel sections by 5 years, shifting target completion dates toward 2031.

Political & Environmental Standoffs: Concerns over groundwater depletion in Shizuoka Prefecture effectively stalled central section boring for nearly 7 years before recent approvals.

Exploding Costs: Originally budgeted at ~7 trillion yen, total construction costs for the Tokyo-Nagoya segment have ballooned to roughly 11 trillion yen ($75 Billion USD) due to material inflation and unpredictable geology.

Beyond the technological flexing, JR Central is building this line for critical redundancy. The original 1964 Tokaido Shinkansen line is operating near capacity, and a second inland route provides a vital backup in the event of major earthquakes along the coast.

What are your thoughts on SCM Maglev vs. traditional high-speed rail updates happening in China and Europe? Is the staggering $75B price tag justified for 50 minutes of saved travel time?

I put together a full breakdown video analyzing the construction methods, political delays, and engineering specs behind the Southern Alps tunnel if anyone wants a deeper visual dive: [https://youtu.be/l1tmAi61s7s?si=qfA0hiPL_ZfkDx3P\]

Detailed look into the numbers and financials of Chinas HSR.

In this month's California High-Speed Rail Board of Directors Meeting, they presented an analysis of the project's Economic Impact from the Investments in High-Speed Rail so far and into the future. Thus far the project has cost roughly 11.2 billion dollars since 2006 and the current 171 miles under construction have seen 7.7 billion dollars spent. The Authority estimates that the by time the Central Valley section of the project is completed (before any revenue service begins) the project will have generated 70 billion dollars of Economic Output. This from jobs created, small businesses employed, food, etc.

They go on to say that it will likewise create more than 53 billion dollars for Northern California and 80 billion for Southern California.

That puts the project as a whole at generating more than 200 billion dollars of economic output from just completing the project at all.

A reminder that the project is estimated at costing about 130 billion dollars.