How modern is the overpass?

We generally build the real ones with a minimum of 24 feet of clearance and we prefer no less than 26 feet.  Older overpasses of course can be lower, especially in the US Northeast and Midwest.

Yes, the tallest* prototype cars are 20'2" high (some autoracks and double stacks), but models of such cars are often a tad taller to provide wheel clearance.

*Note:  I'm not talking about special "high-wide" cars like Schnables.  They can only run on a limited number of routes.

Scott Chatfield

Autorack

My Walthers modern autorack measures 68 mm from the railhead.   I do have one double-stack that measures 74 mm.

UP Standards

Here's what the UP has for overpass standards.

i do not know the measured

i do not know the measured hight.  but if a double stack of “tall” containers fits with a smudge of extra room good enough for me. lucky for me i have a old 3/8 drive socket that fits this perfectly.

for side clearances on curves, ( i run single track) i use the longest car i know of, it is a athearn covered auto rack car.

granted i run as back in the late days of steam early diesel. tightest curve is 26 inches. so i have plenty of room to run most anything.  but anything can run.

When designing a clearance

When designing a clearance for one track to pass over another while keeping the grade as minimal as possible, I used my tallest double stack to figure what was the minimal clearance and went with it.

I model the 50's

But when I was building the railroad I kept an 86' hycube and a double stack around to use as a clearance check on my tunnels, bridges, scenery side clearances and such. I figured if they would clear, then anything that I ran in the future, modern or not would also clear. I've never had a problem.

Espee over Donner

This is what happens when the clearance isn't quite enough

Famous underpass that has had or soon will have it's clearance increased:

Looks like a good place to collect RV air-conditioning units, or at least parts of them.

11foot8

They raised the RR bridge 8 inches: 

It's still collecting stuff: 

The NMRA gage and the modern era

It's a little-known fact the NMRA makes an extension for the NMRA gage to accommodate modern era clearances. The metal gage is only good from 1920 up to about 1969. From 1970-1982, you need to extend the upper edges of the sides an additional two scale feet to allow for higher roofs on equipment. Total height doesn't change, but the upper corner of the gage sides need to go up another two feet.

Come 1983, the total height goes up another scale foot to 23 feet total. Also the side-to-corner height goes up another two feet, and total width increases by three feet.

Here's the NMRA gage extension they sell, if you model after 1982, you need to get and use this extension:

 

I set my Coos Bay branch to match the prototype (built circa 1920), so I used the metal gage without the extension. Later on the branch they wanted to run double stacks but could not because of the tunnel portals -- so my layout duplicates that properly! See the photo:

You can see how the plastic extension helps post 1982 modelers add the extra proper clearances they need.

[shameless plug] All this and much more is covered in my Run like a Dream Trackwork book. At $12 for the ebook, you can buy it, immediately download it, and avoid a lot of lesser known headaches like this when building your layout. [end shameless plug]

Watch your head

It seems like model tunnel portals have always been made too tall, at least for 1960’s and earlier. Apparently few modelers know, or care, how tight clearances used to be. Piggyback service was rather restricted for decades because of limited tunnel sizes, underpasses, etc. Dome cars faced the same problems .Once in a while a layout will be showcased that reflects this reality, such as Bill Neale’s Pennsy Panhandle route set in the 1930’s.

Even today much trackage won’t handle stack cars or other large freight cars.

Barry P.

Tunnels made to early railroad clearances are why the railroads

couldn’t run double stack passenger cars on the east coast. 
I currently model the 1920’s but I clearanced the holes in the backdrop on my new layout starter section to modern height, I forgot the width increased too. I expect that one day I will have an alternative fleet and a few jigsaw scenery pieces to accurately represent the modern era.

Plate C Clearances Clinic at the Elkhart Model Railroad Club

The Elkhart Model Railroad Club on December 7, 2018, had an interesting clinic on Plate C  a railroad car's extreme dimensions. Chuck Hart gives the clinic ar NMRA meetings. Here's a link to a brief synopsis.  https://www.emrrc.com/index.php/home/2018-2019-past-announcements  Scroll down till you see the date. Sorry, it's in our archives and this is close as I can get you.

Jim Ford

Elkhart Model Railroad Club