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Helixes, Tunnels, Spirals, and Other Unique Trackage
Most of us know what a helix is. In fact, I would guess that many of us have
seen one in a model railroad layout, sometimes hidden in a mountain. But how
prototypical are they? Is there such a thing as a full size standard gauge
helix? What about other trackage commonly found in model railroads such as
loops, crossovers, tunnels, etc. Most modelers find a way to incorporate at
least one of these into their layout. Some modelers may go to great lengths to
make sure their rolling stock is prototypical. Do they have a double standard by
using trackage of this sort? The answer is: "Well, perhaps not..."
Some of you may be surprised to hear that one can find examples of all of this
trackage in real life. The purpose of this article is to show you where odd
trackage like this is used on real, full scale railroads.
Much of the information contained in this article was generated by railroad
enthusiasts discussing this very topic on a computer network called USENET. I
have collected, re-written and assembled this information into what you will see
here. While I have found that there is interesting trackage all over the world,
most of this article (except for "helixes") will concentrate on what can be
found in the United States and Canada.
Perhaps the most interesting of all trackage in a model layout is the helix. If
you consider that one revolution of a helix is a loop, you will probably realize
that in real life there are a number of famous "helixes" including Tehachapi
Loop. Can this be considered a helix? Well, maybe. There are many more
examples to consider.
North American Examples
One of the most interesting of such tunnels with loops is right here in
North America. It is in Canada and is called "Kicking Horse Pass". It is on
the CP main just east of Field, B.C. in the Western Canadian Rockies. It is a
series of two tunnel/spirals. The tunnel under Cathedral mountain is 3255 feet
long with a turn of 291 degrees, and the one under Mount Ogden turns through 217
degrees over 2992 feet. The ruling grade is 2.2%. The tunnels were completed
in August 1909, and replaced the route up the "Big Hill", which had a 4.5%
grade. There is a lookout just off the Trans-Canada Highway from which you
could observe both portals of the tunnel. Passengers can ride this route, at
least in the summer, on Great Canadian Railtours' "Rocky Mountaineer" train from
Calgary to Vancouver.
Here is a simple picture showing the general layout.
One amazing piece of trivia about their construction is that when they bored
these tunnels, they were off on one tunnel by 1 and 1/2 feet when the two ends
connected, and 6 inches on the other. Not bad for the technology back then!
There is also a loop on the Bonavista Branch (3'6" gauge) in
Newfoundland. It is called the "Trinity Loop". It has been preserved and is
the site of a railway park called - The Trinity Loop Park. Some of the narrow
gauge Equipment that was used on the Bonivista Branch of the Newfoundland
railway is on display and train rides around the loop are available.
There is a tunnel at Dubuque, Iowa (rather, in Illinois on
the other side of the Mississippi.
Dubuque is in a deep valley (by mid-western standards), and in that
particular part of the valley, the Mississippi is hard against the
limestone bluffs on the east side of the valley, making space for the
city of Dubuque on the west bottom land of the valley.
The Burlington mainline runs up the east riverbank, squeezed tightly
between the river and the limestone cliffs.
Puzzle? How do you build a bridge across the river from the Burlington
to Dubuque? There's no room for a rail yard on the East bank, and the
port of Dubuque was and still is a big commercial operation.
Answer, build the bridge straight across the river, then tunnel into
the cliff for a fairly sharp curve. Here's an attempt at ASCII graphics
showing how it works:
track in tunnel --> / \
-|- |- Double Track Main
-|- <--- CC&P Bridge to Dubuque
Note that the bridge is a swing bridge, and that the swing span is
at the east bank because the deepest part of the river's channel
is right against the bluffs. If the swing span were on the other
side of the river, a curved trestle could have been built out from
the junction into the river, but it isn't easy to put a curve on a
movable bridge span.
In the USA, there are a number of spirals (not in tunnels) in service:
This trackage is east of Bakersfield CA on track shared by the SP & ATSF.
Tehachapi is freight-only with very heavy traffic, and can be viewed effectively
from a car.
This loop is on CSX (former L&N) trackage between Copper Hill and Etowah TN.
Hiwassee would be the most spectacular if it weren't for all the trees in the
area (it goes around the mountain twice).
This is part of a tourist railroad. The loop includes a rebuilt bridge over
the "Devils Gate Viaduct". This line is the former Colorado Central narrow
gauge. Georgetown passenger trains are usually pulled by Shays.
Williams Loop is on the Union Pacific (former Western Pacific Feather River
Route) not far from Keddie, CA. The track winds around a broad valley and
crosses over itself (on a short bridge). It is a good photo spot, but hard to
shoot in its entirety due to the heavy tree cover in some areas.
The Roaring Camp and Big Trees Narrow Gauge Railroad is in Felton, CA. In
Spring Canyon there was a tight spiral with a trestle over a another trestle.
Sometime in 1976 an arsonist burned the trestles. A steep switchback was
quickly substituted in its place. The remains of the trestle still stand. You
can walk down from the summit of the hill, and follow the path that the trains
used to take.
Although no longer existing today, there was some very interesting trackage
centered in Thebes, Il. This trackage included the Missouri Pacific main, the
Illinois Central "Mud Line" (named because of frequent flooding), and the
Chicago & Eastern Illinois. The IC and C&EI had a wye which led to the MP. The
entire trackage had a loop in it.
It seems rather odd from a 1990's context that an out-of-the-way
town like Thebes could be such a focal point for so many lines. But in the days
when bridges over the Mississippi were few and far between, Thebes (and Cairo as
well) assumed importance as locations where freight and passengers were ferried
over the Mississippi.
As time passed, Thebes' importance dwindled. IC's line south to Cairo was
pulled up during the Depression since alternate routes were available. The
remainder of IC's "Mud Line" from Murphysboro was abandoned in the 1960's as far
north as the power station in Grand Tower. MP gained control of the C&EI in the
mid-1960's and, having numerous better routes from Chicago, downgraded and
eventually abandoned the old C&EI main. Likewise, as Cairo's significance
dwindled, the MP line from Thebes to Cairo was taken out of service in the
All that remains in Thebes is the MP's high-speed Chester Sub, now owned by
Union Pacific and used by UP and SP (Cotton Belt) under the joint track
Rifle Sight Notch, Colorado
The upper trestle, built directly over the lower tunnel is located at Rifle
Sight Notch in Colorado. It is on the original Denver, Northwestern, and Pacific
Railroad, built by David H. Moffat Jr. beginning in 1902 (actual construction
over the Continental Divide was in the summer of 1903). He ended his first year
of construction just a few miles past his loop. He used this loop design in his
plan of the descent from Rollins Pass (11,680 ft. above sea level). Roadbed
construction proceded west over the Divide and ran parallel to the Divide for
several miles until it reached a course of descent to lower the line into the
Fraser River Valley. Moffat began his decent down from the above tree line
course he was on, he needed a 200 foot drop to hold at a steady 4% grade or
descent. The loop around the small peak located just away from the main range,
gave the road its steady 4% grade. The tunnel under the trestle caved in many
years ago but the portals are or were still there in 1984. The trestle above is
in ruins and not safe to crawl across as most of the cross ties are gone. A
rough gravel road bed which can be negotiated with 2 wheel drive although it
doesn't go all the way over any more.
Photo 1 (photo from "The Giants Ladder" by Harold A. Boner)
Photo 2 (photo from "The Giants Ladder" by Harold A. Boner)
In other parts of the world there are a number of tunnels with helixes or loops in them!
There are two spirals in New South Wales. One, at Border Loop going into
Queensland, is a "standard" spiral, albeit with an extra tunnel which is not
required as part of the tracks-crossing-over-themselves function. This
link should bring up its
location on a map. The other at Bethungra (near Junee) is more unusual, because
the spiral is on only one of two tracks in a double-track route. The downhill
track is direct, but the uphill track passes over and under not only itself but
the downhill track as well. At one point, there are three "layers" visible along
the side of the hill: the uppermost part of the uphill track, then the downhill
track in the middle, then the lower part of the uphill track. This
link should bring up a map showing its location.
In Bulgaria there is such a tunnel on the Sofia - Karnobat - Varna/Burgas
line. The single-track tunnel is situated at about 150 km east of Sofia and is
4 or 5 km long. The eastern entrance is at about 100 meters under the western
one and the line continues from the western end over a viaduct that crosses both
the valley and the track east from the tunnel (you can actually see the lower
entrance of the tunnel from the viaduct).
There is an example of a loop track (in a tunnel) right
inside the city of Rijeka, Croatia. It was built between WW1 and WW2 when
the city was divided between Italy and then Yugoslavia. This was done in
order to provide rail connection to the main line Rijeka-Zagreb from the
new rail Susak station built in the eastern part of the city.
The "Piggy's Tail Railway Line" in the south of Badian, Germany extends 25.8
kilometers from Weizen up to Zollhaus-Blumberg. It was built in the 1880s for
military (strategic) reasons and taken out of service in 1955 by the Deutsche
Bundesbahn but not withdrawn. Today (since 1977) it is a well known
museum-railway line with steam-locomotives in service.
The absolutely crazy trackage of this line represents the only spiral-tunnel in
Germany. The length is 1700 meters and radius is 350 meters. Only a portion of the
360-degree spiral is inside a tunnel. The altitude gained by this full circle is
15.5 meters. The name of the tunnel is "Grosser Stockhalde-Kehrtunnel". About 60
meters of the tunnel contains straight track.
The idea of this trackage came from Mr. Robert Gerwig, famous constructor of the
Schwarzwaldbahn (black-forest-line in Germany) and supporter of the
Gotthard-line as well. The Wutach Valley line (another name for the Piggy's Tail
Railway Line also has a 180-degree tunnel (called "Weiler Kehrtunnel").
The best that Britain can manage is an open-air spiral on the Ffestiniog
Railway in North Wales. This was built around 1970 as part of the diversion to
complete the re-opening of the line to Blaenau Ffestiniog, the original route
from Dduallt (or thereabouts) having been flooded by a hydro-electric reservoir.
The standard guage line from Bordighera to Cuneo up the Roya valley
and over the pass above Tende has some wild engineering on the southern
ascent including several spirals in tunnel. It isn't as well known as it
might be. It was built by the Italians for strategic purposes and today
the central part of the line is in France but running Italian trains. It
is slightly disappointing to travel in as you emerge from the tunnels so
briefly that all you hjave time to do is realise you haven't a clue where
you are on the rock face before you plunge back into darkness again.
The Rarimu spiral is located in the centre of the North Island of New
Zealand. It climbs about 700 feet in 5 miles and has two loops over itself.
In Norway, on the line from
Oslo to Bergen, you go over a pass at about 2600 meters, and at or
near the summit pass through a town called Myrdal. There exists a local
rail line that goes down the mountain from Myrdal to Flam, dropping from
the 865 meter elevation to almost sea level in a very short 15 kilometers
or so, by using two complete helixes bored through solid rock, you get a
view out about half way down before finally exiting in a valley far below
the beginning point at Myrdal. The line is electrified, and it is a very
noisy ride down through the tunnel (with the brakes and dynamic braking used
to control the train decent). I do not have much on the actual grades etc,
but know there is more info on the web under eurail or scanrail pass sites.
Information provided by Brent Andersen.
In Switzerland there are double loops on both sides of the Gotthard. The old
Furka Oberalp cogwheel line also has a steep helix tunnel at 8% grade and
minimum radius on top of which the highway makes a hairpin turn.
The Gotthard tunnels are on the northern approach to the long tunnel between
Goeschenen on the north and Airolo on the south. On the southern approach there
are four spirals: two close together, curving in the same direction, and two,
separated by a mile or two, curving in opposite directions.
One of the most famous loops is on the south side of the RhB Bernina line (1
meter gauge): a 360 degree spiral viaduct, not in a tunnel but in the middle of
a valley, near Brusio:
,-. | /|\ (up) To Poschiavo - Bernina - St. Moritz
/ \ | |
| | |
\ | /
| \|/ (doen) To Tirano
To get a good view you have to wander up one of the hills nearby. It looks
especially good when a long train is rolling through.
There is also a 2 km long tunnel making a 180 degree turn (there are
actually two parallel tunnels) between Predeal and Timisul de Sus on the
Bucharest - Brasov line in Romania. The first tunnel was built in the 1880s, the
other one in the 1940s when the line was doubled. The average rate of descent
on the 10 km stretch from Predeal to Timisul de Sus is 3.0%, making this section
the most "abrupt" mainline in Romania. The line was electrified in 1965; until
then a 2,000 ton freight train had to be hauled at no more than 20km/h by 4 - 5
Another one is in Serbia, on the Belgrade - Bar line.
Besides "spirals" (or helixes) what other unusual track arrangements are
worth mention? How about "Grand Unions"?
The CNJ had a "Grand Union" -- two lines intersecting
(at 90 degrees in this case) with tracks connecting
adjacent "arms". A train approaching the diamond on any
of the four arms can proceed straight, left or right.
The CTC may have held the record for grand unions, among ICC
regulated common carrier railroads. They had grand unions
under most of the street intersections of the Chicago Loop
district. Of course, it was all two foot gauge traction,
using mine locomotives, but they had something like 50 miles
The CTC tunnels, by the way, were the tunnels that were
flooded last summer when someone drove a piling too close
to one of the tunnels under the Chicago River and cracked
the cement tunnel liner.
According to the DeLorme Atlas&Gazetteer for Maryland/Delaware, there was a grand union in Odenton, MD.
The Canadian National Railways northward line to Barrie (from the Toronto
Union Station) crosses (at grade) the main Toronto East-West bypass (which is
double track) that goes into the CN marshaling yards (North of Toronto). The
Northbound and Southbound trains can both be switched off to either Eastbound
Kansas City, MO:
Kansas City has a complete and active grand junction with two
adjoining "almost grand junctions" all underneath an elevated wye with
one leg passing underneath another, all connecting to a double-decked
double-tracked elevating bridge.
Kansas City also has at least one other grand junction and
a snarl of "air line junctions" and fly-overs.
Topeka has the active remains of a grand junction and a wye
junction connected by an elevating bridge.
Dalhart, TX has the active remains of Grand Junction with a
four lane street passing underneath.
There is a grand union at the P&L Junction, south of Rochester, NY
Where the Lehigh Valley Railroad crossed the Buffalo, Rochester & Pittsburg
Reversing loops are actually quite common. I'm sure there are more, but
here is a list of at least some of them:
Bay Head, NJ:
On the NY&LB (CNJ/PRR) there is a reversing loop so that power did not have
to be run around the train. What purpose does it serves now with push-pull
trains? A conductor on the Bay Head train said: "Well they only have to flip
the seats at the Long Branch end of the shuttle."
Grand Central Terminal:
More well known are the reversing loops under Grand Central Terminal (NYC).
One reason for these is that long-distance trains got cleaned and prepared at
Mott Haven, the Bronx, just north of Manhattan. Incoming trains discharged
passengers at the arrivals platforms at the west side, and then could run
forwards around the loop to go to Mott Haven. This doesn't really explain the
loop on the suburban level, which possibly was used to reduce conflicting train
movements at least for the trains that looped. A loop terminal is more
efficient than a stub terminal since with a loop you shouldn't have to have
outbound and inbound trains crossing.
There are the remains of an overhead reversing loop at Harmon, NY on the NYC
just north of the shops. This loop crossed over the main line. All that
remains now are track supporting structures. The old Harmon loop now serves as a
means to access a condominium project they placed on the river.
There is a loop at Sunnyside Yard that goes under the main just west of
Harold tower. The yard is on the north side of the main tracks that run to New
England and to the Long Island RR. Trains from Penn Station use the loop to
pass under the main tracks and enter the yard from the east or far end. When
leaving the yard, they run out the west end. This is a very nice arrangement as
all trains in the yard face the same way (west/south); the loop serves both to
cross the main and to reverse the trains.
Quite a few of the narrow gauge railroads in Colorado had
reversing loops. Why did they construct loops instead of
a wye or turntable? The reason is because it was necessary
to turn snow plows. A turntable would have been too short
for an engine and a snowplow. A wye would not work because
it would require that the snowplow be pulled backwards
through snow for part of the turning operation.
Cumbres & Toltec:
There are actually two loops on the ex-D&RGW narrow gauge that now make up
the 64 miles long Cumbres and Toltec Scenic RR. The first is at Lava tank
(which is 8-10 miles out of the eastern terminal of Antonito), and this was for
turning the rotaries snow plows and sending them back towards Cumbres. The
second loop (isn't actually completed yet) is located east of Osier and will
allow the train sets from Chama to be turned with a minimum of effort.
The D&RGW usually plowed west from Alamosa and DOWN the 4% grade into Chama, but
if the present-day C&TS needs to clear Cumbres pass, they need to plow UP the 4%
grade which necessitates at least 2 engines. While there was a snow shed on one
leg of the wye at Cumbres, it is actually on the wrong leg when a rotary was
coming from Chama. If anybody was present in 1991 when the C&TS ran the rotary
OY, they realized that other methods were needed to plow that 3rd leg of the wye
since they don't have any way to plow snow while backing up.
There's one still in service at Val Royal on the CN electric
commuter line NW of Montreal.
There's another (freight only) at SP's Colton Yard near San Bernardino, CA.
There was also one at Rockport on the B&M - it faced the stub end of the
branch so engines always backed around it.
The USGS maps for Donner Pass clearly show turning loops on either side of
the pass -- for rotaries and flangers. One of the loops (west of Emigrant Gap)
isn't level. They had to deal with the side of the mountain and it goes off
into the woods and rises up probably 30-40 feet, and comes back down and enters
the main line. Most people on the AMTRAK Zephyr probably don't realize what it
is. Obviously it isn't used except in the worst conditions, so its doubtful
you'll ever see of picture of it in use!
There is a wye on the east side of the tunnel. There is a loop located at
Tabernash, CO which is west of Frazer, CO several miles. The loop is quite
large and includes a small yard and a wye inside
The Stone Mountain RR (near Atlanta, GA) has a circle of track that circles
Stone Mountain (the largest known single piece of granite in the world I
believe) with a wye at one point which connects to the outside RR world (CSX or
NS?). So we have a reversing loop and complete "loop" all in one.
Lambert's Point, Norfolk, VA:
Lambert's Point is where Coal Pier 6 is located, the end of the line for
much of the coal hauled on the Norfolk & Western from West Virginia and
Southwest Virginia. The track makes a wide circuit around the yard and gained
some notoriety several years ago when the J-class 611 made its inaugural run.
The train left Roanoke on a Saturday, headed east to Norfolk amidst great
fanfare. After a overnight stay, the train was to return west to Roanoke on
Sunday. The passengers did come west on Sunday, although the train was late a
pulled by diesels. The J came back much later, tender first, and assisted by
diesels. It seems that the track gauge had been tightened on the balloon track
after the demise of steam on the N&W. When the J started around the balloon
track to be turned for the return trip, the rigid wheelbase of four driving
axles didn't agree with the tighter gauge of the reversing loop. After the J
came near to derailing, the turning project was stopped and heads were
scratched. It was determined that there was no way to turn the engine (the
turntable in Norfolk had long since been removed), so the disappointed
passengers got diesels and the J came back under slow orders, to the Roanoke
turntable, the only known safe place to turn the engine (it was decided not to
chance the engine on any of the several wyes between Norfolk and Roanoke). Soon
after that embarrassment, the N&W did a system-wide check of its tracks to make
sure they would accommodate the J in excursion service.
As you can see, there are plenty examples of exotic trackage. Perhaps the only
difference between that found on the prototype railroad and that which is found
in our model layouts is that:
On prototype railroads, helixes, loops and tunnels were constructed as a
solution to a difficult situation.
On model railroads, helixes, loops and tunnels are constructed, creating
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