There seems to be little impetus to experiment with different track gauges when designing high speed rail systems Is this because of the proven superiority of the standard gauge, or just reluctance to buck the system? High speed rail systems are not usually intermingled with freight rolling stock, so I see no reason to hold to the standard gauge…
The primary reason was being able to use the existing big-city stations.
The Japanese and French, the pioneers in HSR, built entirely new lines through the countryside, but needed to continue to pull into the Tokyo and Paris terminals on tracks shared with other trains. Germany and Italy, too, when they got into the game.
In contrast, Spain had always used a five-foot gauge, but decided to build their HSR lines to standard gauge, for the sake of eventual European through-running, and perhaps, to be able to buy off-the-shelf equipment and special work (track details). That meant they had to build new stations nearly everywhere for the AVE network, and bypass tracks in other spots. They now have some gauge-changing equipment that lets them use their HSR lines for the bulk of the trip, then switch to 5-foot to trundle into Algeciras or wherever.
It helps that standard gauge requires no serious compromises for comfort. The engineering is well known; the center of gravity and crashworthiness already calculated. It’s well-suited for 2-and-2 airplane-style seating with a reasonable aisle. A wider gauge might be easier to design sleeping cars for—but that’s not a big market these days. Narrower gauges saved money on track grading in mountainous areas for some 19th-century roads, but HSR obviously needs gentle grades and large-radius curves to begin with.
The Chinese, African, Southeast Asian, and forthcoming US HSR lines sometimes offer the opportunity to build fresh from end to end, but being able to buy (or copy) ready-made equipment and components seems more appealing than experimenting and going it alone.
I don’t believe that rail gauge per se matters that much - it just needs to be wide enough for stability. While a wide array of custom gauges have been historically used (especially in mountainous regions), the fact that rail gauges are concentrated in a very narrow band worldwide is probably because it’s efficient.
I believe that the original standard railroad gauge originated from the common width of the axles of horse-drawn carriages. As an interesting side note to this, street car and LRT tracks in Toronto are slightly wider than standard gauge so that horse-drawn carriages at the time could roll through the ruts inside the rails. When the first subways were built, it was believed that streetcars might share some of the same tracks, so they were built with the same non-standard gauge, though streetcars never made it down there. You don’t see a lot of horse-drawn carriages these days, but the entire TTC track system remains non-standard.
@ Mr Downtown
Just curious - why does the narrower track gauge save money?
Narrow-gauge railroads can use narrower rights of way, tunnels, and shelves along the side of mountains. They commonly have tighter-radius curves. With smaller cars and locomotives, the track construction can use lighter weight components, including bridges. The British built a lot of three-foot-six (“colonial”) gauge railways in Japan, Southeast Asia, and Africa, and some of those are now being upgraded into modern 200 kph services (HSR on standard gauge typically reaches 300 kph).
Wider gauges can be more stable in high winds; that’s the reason BART (originally slated to cross the often-windy Golden Gate Bridge) chose an unusual wide gauge for its lightweight equipment. A 5-foot-6 gauge was chosen in India because it was thought to be safer in areas prone to cyclones and flooding. However, the much more common reason a number of streetcar networks in North America chose a gauge slightly wider than standard in the 19th century was so the tracks could never be used by “steam railroad” freight cars. It’s sometimes claimed that Russia chose a wide gauge for similar reasons: so Napoleonic France couldn’t run its equipment into the Motherland.
Main thing: Tunnels and track beds are narrower. This cost savings eeally adds up. Plus narrower track gauge means a smaller turning radius.
Thanks, great explanation. That makes a lot of sense.
I misunderstood your first comment thinking it had to do with the physics of pulling the cars etc.:smack:
I did a cycling trip in S. Korea last year. They have an amazing cycling network, literally hundreds of miles of dedicated paths, through the mountains and countryside. Much of it built upon decommissioned narrow-gauge railway routes. We were told they replaced the narrow with wider gauge railways. I guess they now have the money to make wider curves and tunnels.
Very cool experience riding through a smoothly paved mile-long tunnels now lit wth modern led lights.
Except for Line 3 (Scarborough) and the upcoming Line 5 (Eglinton) and Line 6 (Finch West). 
*Though technically Line 5 and Line 6 are being built by Metrolinx, not the TTC. And Og alone knows what the Ontario Line (Line ???) will be…
Duplicate
It’s a bit like the QWERTY keyboard. Even if there was a better gauge, the sheer amount of existing track means that 4’ 8½" will remain the standard.
The ruts in Roman roads were generally around 5’ apart because the width of a cart had to conform to the width needed to fit a carthorse between the shafts. Early rails were all different gauges at first, but Stephenson went for 4’ 8" as the inside gauge, and this was eased an extra half-inch to allow the carriages to take curves more easily.
Brunel went for a broad 7’ gauge on the Great Western Railway to allow for more comfortable trains, but that had to be re-worked around 1900 to match the rest of the network.
Of the two main subway lines in Philly, one (Broad St.) is standard gauge and the other (Market-Frankford subway elevated) is 5’ 2.5" which is described as Pennsylvania trolley gauge. I once read that that was to avoid ever being incorporated into a long-distance railroad. Curiously, the cars are noticeably narrower than those of the Broad St. subway. The Broad St. line was built a couple decades later. That stations on the Market-Frankford line cannot accommodate wider cars.
Would it be possible in principal to rebuild tracks in, say, Tokyo station, that could accommodate two different gauges? I have something like this: || | in mind. The switching would be complicated but essentially one-off.
>I have something like this: || | in mind.
That’s called gauntlet track, and there were once many examples all over the world. It allows narrow gauge and standard gauge equipment to pass, or even to stop at, the same platforms. It also could be used to allow freight cars with a wider loading gauge to pass high-level platforms without scraping. I suspect there’s a fair amount of gauntlet track in Spain, letting the standard-gauge HSR equipment run through small town stations without need of their own bypass track.
While it works fine for villages with two tracks passing a middle platform, you can see that it wouldn’t help with a metropolitan terminal such as Tokyo or Gare du Nord, which have several tracks and high-level platforms running parallel.
They already have this. The main lines in Japan are narrow gauge, while the Shinkansen (high-speed) trains are standard gauge. There are many locations where the tracks are combined. Speed is limited on the dual-gauge track as the narrow gauge trains in the opposing direction are susceptible to being blown over by trains passing at too high of a speed.
I can’t think of any Japanese central city stations where both gauges use the same platforms, though.
Naturally, in urban Japan, you want platforms to reach right to the train’s doorsills for rapid loading. While there’s probably no technical reason trains of different gauges have to have different width of the cars themselves, in practice there has always been a few inches difference. Japan’s “Cape gauge” (1067mm) lines generally have equipment 3000mm wide, while the standard gauge (1435mm) Shinkansen use equipment 3400mm wide.