# Tunnel height



## Mseav

In an HO layout, what is the minimum height for a tunnel? Ive measured my cars and it seems 3'' is enough. Is there a standard minimum?


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## johnfl68

For HO "Modern" it would be 3-5/32" minimum height.

You can look at the table if you need more information:
http://www.nmra.org/sites/default/files/standards/sandrp/pdf/s-7_2012.02.pdf

John


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## traction fan

*Clearances*

Mseav:

The minimum height,and width, of a tunnel, or even a track side structure's loading platform, can all be measured with an NMRA gauge for your(HO) scale. If you don't already have one, buy one. They can measure dozens of things besides minimum clearances. This is a basic and essential tool. It comes with good printed and illustrated directions and is well worth having.

Regards;
Traction Fan


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## gunrunnerjohn

Remember, if you put the tunnel on or close to a curve, remember to account for the greater width of locomotives, especially articulated models, as they round the curves.


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## CTValleyRR

gunrunnerjohn said:


> Remember, if you put the tunnel on or close to a curve, remember to account for the greater width of locomotives, especially articulated models, as they round the curves.


I discovered that the hard way on my first layout. I installed a tunnel in one corner of my layout, and was test running a GP-40 and a string of several cars. Loco starts into the turn... and BANG; comes to a halt as the steps hit the tunnel portal. Most of the cars derailed. D'oh!


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## tkruger

For me the minimum size is that of the diameter of my arm. This is for three reasons, 1. It is bigger than any of my locomotives or rolling stock, 2. Something will inevitably derail in the tunnel, 3. I have to clean the track in there. Now the part I forgot about was making the tunnel longer than my arm and curving it, thus I need a stick to get at anything near the far end of it.


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## dave1905

Railroads have various clearance diagrams for tunnels. an NMRA gauge is your best bet. Modern vertical clearance is 24 ft above the top of rail (3.3 inches or 3 5/16 in). That will clear auto racks and double stacks.


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