Rathole tunnel

Rathole tunnels are railway tunnels where fumes from locomotives make passage through the tunnel unpleasant.
Overview
Rathole tunnels are characterized by being long, steeply graded, narrow bores (often with single tracks). Their locations may also be subject to unfavorable winds that prevent smoke from clearing the tunnel.
Some of these features are caused by the tunnels having to be unusual shapes (such as incorporating an S shaped bend in the middle), or changing gradient in the middle.
Examples of Rathole Tunnels
Australia
* Ardglen Tunnel in New South Wales - Garratt locomotives prohibited, because of heat problems in the narrow bore.
* Coalcliff Tunnel in New South Wales - restricted loads for heavy 57 class engines, so that engine need not work at full blast.
* The old Otford Tunnel, Otford, New South Wales - notorious for suffocating fumes - at ruling 1 in 40 grade - sea breezes often blew smoke along with train. c1880.
* The old Lapstone Tunnel that replaced the Lapstone Zig Zag was built too steep and eventually had to be replaced by a gentler alignment.
* The 10 tunnels at Lithgow that replaced the Zig Zag Railway were sometimes considered to be rathole tunnels, but the gradients were fairly gentle at 1 in 90 (1.11%), the tunnels were double track, and the gaps between the tunnels allowed for some intermediate ventilation. The western approaches were graded at 1 in 42 and required use of Bank engine helpers only in the open air. This deviation was opened in 1910.
* The 3 tunnels on the Ulan line in New South Wales, in particular the long Bylong tunnel, have tight profiles. The Australian Rail Track Corporation have planned timetabling to allow the tunnels time to clear through natural air movement during the headway between trains but, with the construction of new passing loops on the line, headway will be reduced and investigations began in 2007 for installation of forced ventilation, possibly using shafts that were used during construction. There were earlier problems with the operation of 3 locomotives on trains, where the fumes from the first engine starved the oxygen to the following engines. This was solved by relocating the air intakes to a lower position.
* The Rhyndaston Tunnel in Tasmania is 955 m long with a small bore, and is graded at 1 in 40.
* The Western Australian Government Railways had one tunnel in steam days. A fatal accident occurred when a Garratt-hauled train stalled, and the footplate crew were unable to escape past the hot cylinders.
Germany
*Cochemer Tunnel, 4205 m long double-track, opened 1877; ventilation system 'Saccardo' installed in 1904, ventilation shaft added in 1913, electrification 1976
Italy
*In the Balvano train disaster of March 3, 1944, over 500 people who stole a ride on a steam-hauled freight train died of carbon monoxide poisoning when the overloaded train stalled in a steeply graded tunnel.
New Zealand
*Lyttelton rail tunnel, originally steam, was electrified, now diesel
*Otira Tunnel, steep grade (1 in 33), originally electrified, now diesel with special ventilation
*Tawa Flat deviation, steep grade, with a long Tawa No 2 tunnel, electrified
United Kingdom
*Oxendon Tunnel
*Kelmarsh Tunnel
*Woodhead Tunnel Woodhead 1 & 2 (dating from 1845); but Woodhead 3, opened in 1950s was wide-bore twin tracked electrified.
*Combe Down Tunnel on the Somerset & Dorset Joint Railway was a narrow mile long bore with a grade of 1 in 100 on a line with a ruling grade of 1 in 50.
*Dove Holes Tunnel
*Privett Tunnel
*Fowey Branch Tunnel incorporated an internal change in gradient, where a metal gong alerted engine crews to the fact.
Switzerland
*Ricken-Tunnel, 8604 m long single-track, gradient 15,75 ‰, on October 4, 1926 9 railwaymen died of carbon monoxide poisoning while their train came to a halt in the tunnel, electrified 1927
United States
*The first Cascade Tunnel was built to replace an unsatisfactory quick-to-build section of line with 8 switchbacks, problems with snow, steep grades, train length limits. Unfortunately, the first tunnel was quite long at and had a steep gradient of 1.7%, and had severe problems with smoke, qualifying it as a rathole tunnel.
*The second longer Cascade Tunnel long was built with gradient of 1.565%. It was originally electrified. However when dieselisation came, the fume problem resurfaced, requiring a ventilation system to be installed to clear the air after each train.
*The same problem can also apply to the 6.2 mile (10.0 km) Moffat Tunnel. In its route guide to the California Zephyr, Amtrak advises passengers not to cross between cars while the train is crossing the tunnel .
*Winston Tunnel on the Chicago Great Western main line in northwest Illinois, with approx 0.95% grade. Despite being less than long, the poor design of the tunnel meant that fan ventilation was required during the period that steam locomotives operated through it.
*The main Sierra Nevada line of the Southern Pacific Railroad (now Union Pacific) between Roseville and Reno (known as "The Hill") has lots of tunnels, tight curves, and snow sheds which may pose problems to crews. This led to the development of its unique Cab Forward Mallet locomotives.
*Cincinnati, New Orleans and Texas Pacific Railway: The second district is nicknamed "the Rathole Division."
Rathole Tunnels Without Problems
*Box Tunnel on the Great Western Railway, built ca. 1838 was never a problem, even though it is quite long at about , and has a relatively steep gradient of 1 in 100 (1%), because:
**It is double track;
**Its dimensions are large compared to the rolling stock gauge of the trains, since the route's conversion from (broad gauge) in the 1890s (note though that the monumental portals were an act of propaganda when it was built; the tunnel narrows to the proper size inside)
**There are several air vents along the way (though this is normally the case when tunnels are constructed, there was worry of asphyxiation in the tunnel when it opened so excess were provided)
**trains rarely enter tunnel from standing start (due to the closure of Box railway station)
**double headed trains are rare.
*While the Unanderra, New South Wales to Moss Vale line has steep continuous grades of 1 in 33, the grades ease to 1 in 100 through the tunnels on the line.

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