choosing track gauge

[miyakoji]

I was just looking back at my thread on JR East's standard gauge non-shinkansen rolling stock, and I reread Eliphaz's comment about Tokyo Metro's Ginza Line maintenance facility.  I think I read that JGR chose Cape Gauge for Japan because it makes for easier negotiation of tight turns, but I can think of several subways and trams I've been on that go through tight turns yet use standard gauge or wider.  Does anyone know how this sort of thing is decided?

[KenS]

Narrow gauges (meaning any gauge narrower than Standard Gauge, 1435 mm) are usually preferred over Standard Gauge or broad (wider than standard) gauges due to lower construction costs (lighter rail, shorter ties, sharper curves and steeper grades all lower construction costs).  And if your trains are lightweight and relatively slow-moving, they don't have significant drawbacks, although ultimately the inability to handle longer and heavier cars hurts the operating costs and typically makes such lines less profitable.  As railroads "grew up", with heavier cars and faster speeds, wider gauges became attractive because they spread the load over more square feet of dirt, allowing heavier cars,  and they are considered to be more stable (just how much more stable is one of the longest-running design arguments in railroading, although I think it's generally accepted as true today).

 

The effect of gauge on acceptable curve radius is a complex one, and something I don't fully understand after years of studying railroads, but older cars typically had fixed axles, rather than pivoting trucks, and this probably had some relationship to narrower gauge being better for sharp curves (the short length of older cars factors in also).

 

I've seen several comments by Japanese writers (and writers about Japanese trains) that the reason for Japan's use of Cape Gauge  (1067 mm) is not known, but one speculation is that it was chosen because the early railroad designers were British, and the British tended to use Cape Gauge for railway construction in their colonys (probably due to the usual cost reason). The post-Restoration Japanese government was also quite poor (they had to issue bonds in London to finance the original Tokyo-Yokohama railway) and so minimizing cost was probably a very important consideration.

 

And Japan's trams often used Scotch Gauge (1372 mm) even though they probably had sharper turns than most narrow gauge lines.

[bikkuri bahn]

To add to Ken's response, many private railways (particularly in Kansai) use of the 1435mm standard gauge arises from their origins as street railways rather than trunk lines.  In fact all standard gauge private railways from the start were electrified (with the exception of one line on Shikoku's Kotohira Rlwy).  As for private railways utilizing the 1067mm gauge, it allowed/allows interchange of freight traffic with the JGR/JNR/JR system.

[Nick_Burman]

(with the exception of one line on Shikoku's Kotohira Rlwy). 

 

The Shionoi (?) Onsen line was a separate operation which was taken over by Kotoden but closed some time in the late 1920's-early 1930's. Judging by the short description of in "Electric Railways of Japan" the line looks like one of those projects which was conceived as an electric line but which flopped because of insufficient capital.

 

Cheers NB