It’s no secret that many railroad old tunnels in the east won’t accomodate high-level passenger and freight cars because those were built before the taller cars became popular. I am getting read to construct one of those older tunnels on my branchline and I googled to try to determine what the minimum tunnel height would have been for a tunnel constructed in the first half of the 20th century. I was unable to find a definitive answer.
My research told me about standards for loading gauge which specifies the maximum height and width of railcars and structure gauge which refers to height and width of tunnels and other objects a train might pass through. I did discover that the old loading gauge height maximum was 14.5 feet for passenger cars but that was increased to 16.5 feet when hi-level passenger cars came into being. For freight cars loading gauges varied from 15 feet 2 inches to over 20 feet for double stack containers. None of that tells me the minimum structure gauge for a tunnel in my era and locale. The tunnel of course would need to be higher than the car to allow for wobble but I don’t know how much higher than would need to be.
Was there a minimum height standard for railroads in the first half of the 20th century or was it whatever the railroad decided it needed to be. Does anyone know what that minimum height would be.
When UP was opening up their tunnels in California for double stacks, they allowed for a 3" clearance at each corner. That’s what I recall anyway. It’s been a long time since I worked on that project.
That’s 1/32" for us HO people.
But, to the subject. I went through an assortment of search terms. So far, the best seems to be “railroad tunnel cross section” in image search. Of course, almost all are for revoltingly modern, even unbuilt, tunnels.
It seems unlikely anyone would build a tunnel larger than they needed or MIGHT need. So, if the branchline was always a branchline and was never going to “enlarge”, the tunnel would be rather tight.
I expect they woulda taken the dimensions of the biggest car they ever ever ever thought might pass through the tunnel, allow for clearance for a man lying down on top and clearance for a man hanging on a car side, added the appropiate best-wishes extra, and built either a “square” framed tunnel or maybe a roundtop in rock.
I recall a possibly true story of a problem when they tried putting an excess height car through a tunnel on the California Western–shutting down the railroad for awhile.
Ed
PS: You can bet someone wrote an engineering book on the subject (design of railroad right of way) back in the '20’s or '30’s.
I thought of using my NMRA gauge but then realized that is probably set to accomodate modern hi-level passenger cars and double stack containers. That would probably be higher than wha
That’s some really good information and a few of those tunnels are in the same region my freelanced railroad runs through (Northern New Jersey, Southern New York). Unfortunately I couldn’t find specific heights for those tunnels but the links contained pictures of these tunnels which will be helpful in configuring the geology around the tunnel. Just looking at the varying heights of the tunnels makes me believe there wasn’t a standard height and the railroads just built what they believed was necessary to accomodate the tallest rolling stock they anticipated plus a little extra for a crew man lying down on a roofwalk. I’ll be sure to add telltales at each end of the tunnel.
I sometimes have to cut my overhead clearance to the lowest I can get away with and still clear either my Trix GG1’s extended pantograph or the smoke stack on my wrecker crane. Turns out it’s 4.1" and that helps the tunnel to look nice 'n tall for the rest of my fleet. If I were not going to use a portal for either of those, and not my True Line CP Rail caboose (with it’s extra tall stack), I have found that all my rolling stock clears 2.8", and it doesn’t look too bad. That is, it’s quite tight, but doable. A critic would have a valid point if he said it wouldn’t meet the FRA or whatever engineering standards in the 1:1 world.
My railroad is freelanced but the history of the branchline I authored has the branchline being built in the 1920s so I want my tunnel to accomodate the rolling stock of that era plus room for crew men on the roofwalks to lay down and be able to safely clear the tunnel. I don’t know to what degree engineers in that era would have anticipated taller rolling stock. That’s why I was hoping to find out if there was a standard minimum before I began constructing my tunnel. Construction of the tunnel is still a few days away but if I don’t find out anything different, I think I am going to go with a 2.5 inch high tunnel (HO scale). That’s over 18 scale feet and would easily accomodate any rolling stock of the era I am modeling which is mid 1950s. In addition since this tunnel will bore through a solid rock outcropping, I’m planning to build it with no lining or portals. In researching tunnels I have discovered a number of tunnels which were bored that way. It’s not the norm but I think it will be an interesting feature.
I have only one tunnel on my railroad, as there weren’t too many railroad tunnels in southern Ontario (my trackplan - or lack of it - necessitated it). I sized it to suit my ‘30s-era rolling stock and locomotives…for the most part.
I later acquired some JJM Railroad Enterprises’ automobile frames to be used as gondola loads…
…which won’t fit through the tunnel nor under a couple of low bridges. Fortunately, they are in dedicated service, and simply shuttle back and forth betwen their point of origin and the destination where they’re unloaded, which doesn’t involve the tunnel or those bridges. The cars must always travel with the support rack on the south end (railroad direction) of the car, though - this is for loading and unloading conditions. If the empty car is inadvertently turned, it must be turned before going back to be re-loaded. The turning wye for this is under those two low bridges, and the car and rack, empty, does fit under those bridges.
This situation was done deliberately, and there is also some MoW equipment which can’t use the wye (but will clear the tunnel). Restrictions like these can add operational interest, but you don’t want to carry them so far that regular operations are disrupted or become impossible.
I have a specialty car under construction that required using a recessed flatcar to clear my tunnels and bridges.
Keep in mind it’s easier to have a bit more clearance during your construction than modifications later on for future needs. When I designed and built my layout 30 years ago I had no idea that I would be building a wireless camera car to run my tracks.
Mel
Modeling the early to mid 1950s SP in HO scale since 1951
Most railroad tunnels in the eastern US were built earlier than that, sometimes as far back as the 1840s. There was no regulation as far as the size of the tunnels at that time, I don’t know that there ever has been. I suspect railroad / engineering organizations may have had a set of ‘recommended practices’ but the railroad buidling the tunnel could pretty much build what they want.
One way to get the information you want might be to check the MR archives for old articles on building layouts with tunnels. The NMRA and other specs for height required under bridges, in tunnels etc. was less back before ‘hi-cube’ and vista-dome cars came along, so maybe check articles from the 1930’s to 1960’s. (Nowadays articles often talk about a 4" clearance, but seems to me many older layouts were built with 2-1/2 to 3" clearance in HO.)
It looks like most tunnels through rock were cut with a circular top (maybe to remove a stress fracture point). Since most house cars are flat topped, I would think that the 2 1/2" height should happen at the car corners(ish). Except that a man flat on the car won’t likely be at the corner.
So, the max height of the tunnel will be more like 3". Or maybe 2 3/4" while lessening the corner clearance.
I have a specialty car under construction that required using a recessed flatcar to clear my tunnels and bridges.
Keep in mind it’s easier to have a bit more clearance during your construction than modifications later on for future needs. When I designed and built my layout 30 years ago I had no idea that I would be building a wireless camera car to run my tracks.
Mel
Modeling the early to mid 1950s SP in HO scale since 1951
I did notice that and I plan my tunnel to have an arched top. I was looking at some of the tunnels which DSchmitt provided a link for and several of the tunnels looked to be quite short by modern standards. I didn’t find any actual documentation to tell me exactly what the heights were but using people standing near the bore as a scale, I estimate one of the tunnels which is very close to where my fictional road is located had an arched opening that I estimated to be no more than 15-16 feet high. Further reading on that tunnel told me its height became a problem in later years.
I was thinking along those same lines. Given my era and locale there is zero chance any of the modern high equipment (Superliners, double stack containers, etc) would ever need to travel down this line. The tunnel I plan will accomodate the railcars that I plan to use on that line. If at some future date I want to run taller equipment, I will face a very prototypical dilemma.
I was hoping to hear that there weren’t any set standards for tunnel height and that seems to be what you are telling me. My research has shown several tunnels that I estimate to be no taller than what I plan.
Not sure of the exact dementions, but a few years ago they lowered the track in the tunnel that goes under Bellows Falls, VT. Before the project started there was a front page photo of an Amtrak FP-40 coming out of the tunnel, I wouldn’t wanted to have been a flea on either the top or a side, it filled the tunnel. Measure your tallest car or loco and make it just fit, just barely.
