The parallel tracks are probably no more than 3 feet apart. If they were further apart, wouldn’t the risk of a train tipping over be greatly reduced (especially in the case of a derailment)?
So why are they so close together?
WAG: Wider tracks = harder to turn? (Larger turning radius).
You may also want to read The Master’s comments on the origins of railroad gauges.
Those responsible for building trains and train tracks (and those affected by trains tipping, e.g., passengers, cargo haulers, etc.) apparently believe that the risk of trains tipping is currently at a reasonable level.
Sure, they could make them less likely to tip by making the tracks wider, but you don’t posit any reason why they would need to do that, and doing so would undoubtedly have some negative effects.
Automakers could also make people less likely to be injured in a crash by installing NASCAR-style roll cages, seats, and restraint devices, but people are obviously comfortable with the current level of crashworthiness of cars.
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- There are mountain train systems with gauges as narrow as three or two (!) feet, however usually the traincars used on these aren’t as large as standard railcars.
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- Also, when trains derail, it’s usually not because they tipped over. It’s because the rails were heated up to the point where they warped apart (as in a forest fire) or the rail bed was damaged and the ties went soft, allowing the rails to be forced apart sideways (as in a flood).
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Remember too that the bulk of a car’s weight is on the bottom. The cars themselves are mostly hollow, and all nearly all the motors, A/C compressors, blowers, braking systems, power transformers, etc. are mounted on the underside, so as a result, the center of gravity is very low. When trainmen obey signals and speed limits, trains never tip over in normal operation. In a derailment, a wider wheelbase probably isn’t going to help much.
Advantage of narrow gauge: smaller curve radiuses possible (hence lower construction cost for a railway built in hilly terrain, because the line can follow the contours better, needing less bridges, tunnels and cuttings).
Advantage of normal (1435 mm/4 ft 8.5 in) or wider gauges (Russia 1524 mm/Spain 1600 mm): higher speed and higher load possible.
The original railroad lines chose narrow or normal gauge according to these tradeoffs; the gauge of new lines is of course determined mostly by the need to be compatible with the existing system.
Isambard Kingdom Brunel’s Great Western Railway in Great Britain adopted a gauge of 7ft 0.1/4’;
This was probably the largest railway gauge ever used on a main line railway, or railroad;
the trains were slightly more stable, perhaps, but were much wider and comfortable (by all accounts).
If railways were to be introduced to new routes with new technology I would recommend a wider gauge,
although it is technically only the structure and loading gauges which need to be increased in most cases;
- the Shikansen bullet trains are very wide and fast but run on 4’ 8.1/2" gauge tracks with no particular stability problems.
Warning: RR geek answer follows:
On modern American railroads the rails are 4’ 8 1/2" apart. Prior to the middle of the 1800’s there was more variation. One RR, the Erie, I think, was built to either 6’ or 7’ gauge and many southern railroads were built to an even five feet between the rails. One consideration was that wider tracks cost more to build since more earth moving and surface preparation was needed, and over time as the wider and narrower spacings were compared, the extremely wide ones weren’t seen to offer significant benefits.
As freight car interchange between railroads became more common it also became a real economic benefit not to have to switch out the wheels under the cars as they moved from one railroad with different rail spacing to another. In the 1860’s the first transcontinental railroad was built, and the gauge chosen for it was 4’ 8 1/2", and this pretty much became the default choice for all new construction. Some narrower gauges were used (2’ in the northeast and 3’ in quite a few other places), but these RR’s almost all operated as isolated industrial lines or were later converted to standard gauge or closed.
As Q.E.D. mentions, the center of gravity for RR equipment is pretty low and it’s hard to tip over a modern locomotive ar railraod car unless it’s improperly loaded (on lumber cars you’ll soimetimes seem printed warnings to unload both sides of the car equally to prevent tipping. I once worked on a 3’ gauge tourist railroad and our biggest concern wasn’t tipping but hitting somehting that could lift the wheels off the tracks.
The streetcars (trams) in Toronto, which for historical reasons no-one can quite figure out run on broad-guage track (4’ 10-3/4" I believe), are quite noisy on the curves. I suspect this is due to wheel rubbing/slippage when wheels connected by solid axles can’t travel different distances on the inner and outer rails. In many places the rails are continuously lubricated by water to reduce the screeching.
The trams in Helsinki run on narrow-guage track and seem to have a much easier and quieter time going around the tight in-street curves.
Tipping over, however, is the least of their problems. As opposed to crazoid drivers.
More railroad geekery ahead…
The first lesson many railroad civil engineering students are taught the first day in class is “Never forget that the railroad tracks are too darn narrow.” The allegation is that if engineers were doing American railroads (primarily freight) all over again, the track gauge would be at least six feet (the width of the original broad-gauge Erie mentioned above). Insofar as that goes, the only such completely-independent rail network in the USA constructed in recent years to a broad gauge is the passenger Bay Area Rapid Transit (BART) in San Francisco at 5’ 6" gauge.
Narrow gauge was originally marketed/developed as a lower-cost alternative to the standard gauge. The rationale was that equipment, construction, and right-of-way costs would be incrementally lower (say, 40%), just as costs for bigger/broader trains would be incrementally higher. However, the noted historian George Hilton, in his book “American Narrow Gauge Railroads”, explained that this theory was a fallacy–that costs were lowered only minorly (say, 25%) for a much larger reduction in actual system capacity (40-50%). Apply some of the same logic to a highway or a pipeline–if you’re buying right-of-way or building a bridge across the river anyway, it isn’t that much more expensive to build it for eight lanes rather than four.
Minor differences in track gauge in city transit systems–such as the aforementioned Toronto case, Philadelphia’s 5’ 2 1/2" gauge, or Baltimore’s 5’ 4 1/2" gauge, were typically mandated by city planners in the 1800s as a condition of allowing then-private companies the franchise to construct tracks in the streets. By mandating an “incompatible” track gauge, the city fathers saw to it that the trackage ostensibly only for transit uses could not be also used for haulage of freight cars down the same rights-of-way.
Adolf Hitler, in his last days as dictator, actively proposed and planned a massive European network of broad-gauge trains with a track gauge of three metres (over nine feet!). This system would have featured multi-story, cruise-ship-like passenger trains and freight trains almost big enough–with careful handling–to handle small Navy vessels over land!
In spite of the argued advantages of larger-gauged trains, the bitter reality is that no one has yet to propose any independent system (aside from operations like BART) where the advantages of “broad-gauge” would overrule the practical advantages of “off-the-shelf” technology in stock and mass production. It’s very much like the overwhelming use of Microsoft Windows and IBM PC units–they both have far superior alternatives, but simplicity and cheapness of “conformity” win out, for better or worse.
Hmm, this is very interesting. So is that BART system the largest, private alternate-guage railroad?
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BART, being a public transit system, is hardly “private”.
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5’ 6" (1,676 mm) gauge is in use in India, Pakistan, Sri Lanka, Spain, Portugal, Argentina, and Chile; 5’ 3" (1,600 mm) gauge is used in Ireland, South Australia and Victoria (being standardized to standard as we speak, I recall), and Brazil; and 1,520mm gauge (5’) in Russia. Most of these countries also have/had smaller networks of narrower-gauged rail lines.
The “off the shelf rolling stock” cost advantage seems to be quite significant. When Spain built its first high speed line (Sevilla-Madrid, opened in 1992) they built it in standard, 1435 mm gauge (i.e. incompatible to the rest of their network) rather than having the AVE trains they bought (basically French TGV trains) redesigned to the Spanish 1600 mm gauge.
Ok, yeah, cool. One more question. Why on earth are the gauges measured in mm? I mean, 3 feet plus is a bit much to be differentiating in mere mm don’t you think. What’s the origin of this crazyness? Or is it crazyness? Do you like Chili?
–J
I have not checked this out, but I will share what I have been told. Train tracks were originally the width of passageways that originally accommodated a chariot. Chariots were wide enough to be pulled by two horses. So it all started with a horse’s ass. I am open to being pointed out and laughed at…
Zoe, did you read Earthling’s link? 
FlyingScotsman: So what is the largest, private, alternate-guage railroad?
Hmmmmm. This is (inadvertently) a real poser. It hinges greatly on your definition of “private”. Except for the United States, every other system in the world either is a state-run or state-subsidized system (much akin to socialized highway and airports/airlines), or was originally built as a private system but eventually nationalized or swept under state control (Europe, Japan, South Africa, etc.). There are of course variables to all of those factors–for convenience, we’ll ignore such stuff as state charters and land grants given to early US railroads, the precise definition of what Amtrak is now, recent privatisation of former state networks in the UK and elsewhere, etc.
By far the largest non-standard network in mileage was the former Soviet system, now Russian, with its five-foot gauge, but it was, and still is, a “state” operation. The same can be said of the nationalised networks of Spain and Portugal, of the 3’ 6" gauge South African network, etc. Likewise, I would have to check into whose money went into the various Australian mongrelized network of various gauges–I think some were private and others government-funded. I’m even forced to weigh just how big the Southern U.S. five-foot gauge network became before the Civil War.
It’s possible that, sticking strictly to a narrow definition of “private” that the answer lies in the three-foot-gauge “empire” of railroads in Colorado and Utah, primarily the Denver & Rio Grande, the Rio Grande Southern, and other lines, which eventually were operated under the wing of the Denver and Rio Grande Western (standard-gauge) Railway as late as the late 1950s, which at its maximum amounted to well over a thousand miles of three-foot network. But that’s not necessarily what you were asking me, is it?
Interesting, but not quite what I was getting at.
I know some large industrial complexes have rail installed to move things around in their own plants, and, presumably, to move goods out into the main rail system. Obviously, it would be logical to use the standard guage throughout. What I was actually wondering about is if there are in fact any such “private industry” rail systems that do not use the standard guage?
FIRST, IT’S SPELLED “GAUGE”, NOT “guage”!!! My next question for Cecil is how in HELL people keep misspelling the word that way!!!
If that’s the extent of your query, most certainly. Most coal mines, for example, when they used underground tunnels, used narrow gauge (anything from two-foot to four-foot, with lots of three-foot and 42-inch), since mine cars never went directly on the network, but instead dumped into coal-sorting tipples. The same applies to quarry railroads, most famously the Welsh two-foot (well, 1’ 11 1/2") slate quarry roads like the Ffestiniog, the Tallylyn, the Corris, the Welsh Highland Ry., etc.
Steel mills used anything necessary, from little trains hauling ore or scrap to giant wide-gauge tracks for moving self-dumping hoppers of processed ore. But even “torpedo” cars of molten metal and/or intra/inter-plant shipments of hot metal castings are done primarily on standard gauge.
Even considering the other factors, there usually has to be a compelling reason for even a private, non-connected railroad system to be “noncomformist”, as it were. Take the example of a steel mill–they could (and did) acquire used gondolas or hoppers from the regular freight railroads, abuse them further in in-plant service for another few years, then cut them up and heave them into the furnace!
I’ve had it pointed out to me that there was apparently a logging railroad on the Pacific Coast USA built to a gauge of eight feet. Logging railroads tended to be temporary affairs, mostly built to three-foor or standard gauge (locomotives for those gauges were available “off-the-shelf” from most loco builders; an oddball like a six-footer would be a custom job).
Again, it comes down to conformity. Unless you have very special needs, is it worth your trouble to order special customized computers with a high-efficiency operating system, or is your company going to do everything it needs with off-the-shelf computers with Windows XP and Office–or, for that matter, a five-year-old computer running Windows 98?
Oops! Thanks for the tip, Trigonal Planar and for the link, Earthling.