HO Model Train Layout Guidelines


HO Model Train Layout Guidelines
Some basic tips for drawing railroad layouts are offered in this article. These guidelines can be used for any scale layout, I’ve used HO because it’s very popular, and the scale I am most familiar with myself. If you are modeling at a different scale, I have several articles outlined the exact details them, in my Tips For Model Railroaders.


The first step in planning your model train layout is to know what scale you are going to work at, and what the overall dimensions of your layout will be. Sketch some rough ideas on paper to get a feel for what you want and how it will work in the amount of space you have.
A good idea is to establish minimum dimensions for your layout such as the minimum curve radii, switch turnout angles and maximum grades. The rolling stock you want to use, and methods of operation, help determine these design elements of your layout. If you are running short trains with just a few cars and engines, then 18″ minimum radius curves will work fine. On the other hand, for larger and longer, you may need curves of 30″ radius or larger (HO scale).
What is the maximum grade you can use?  A 4 or 5 percent grade is rare in prototype railroads but you may need it in your model due to the amount of space you have. If you are planning for one track to cross over another, you must have enough length of track to rise 3″ to 4″ (HO scale) without getting too steep for your models. (Note – prototype railroads rarely go above a 3 percent grade. If you want your model to be completely accurate, then you will also be limited to this amount of grade.)
Model Railroad Clearances
Take extra care when one track comes close to another. Ensure that there is enough clearance for two trains to pass, otherwise the cars will collide and derail. This is especially critical at curves. When the railroad car is on a curve, the ends go over the track width. And, the middle of the car is forced to the inside of the track.
The longer your rolling stock, the more offset you need between curves. You can check this visually by placing your longest and shortest rolling stock on a section of curved track to see the overlap. Set two sections side by side, place your longest locomotive or rolling stock in them, and see for yourself.
Layout Drawing Techniques
A simple way to draw your ideas of a railroad layout is to begin by drawing all the outside dimensions or fixed objects (such as the outline of the room, posts, etc.). Once these fixed objects are located on the drawing, then fill in around them with the track.
Draw in the important scenery, buildings, roads, etc. If you are replicating some real place, work from maps, or perhaps even measurements you took on a scouting visit! Many modelers fine they have to “compress” space, leaving out some of the longer distances, so they can get it all in. That’s fine.
Locate the major curves of your layout next. You know which corners will have a 90 degree turn on the layout. Place a circle in this corner drawn to the radius that you think you need. Place circular arcs in all the corners of the main line. You will connect the circles with your main lines later.
Then select where any switching yards and sidings will be. Using your plan you can try different locations, unless your plan is replicating some real place.
Once the important curves, yards and other objects have been drawn in, begin connecting curves with straight lines. You may want to use broad curves to connect different areas on the layout (instead of straight lines). You can always make adjustments later.
Then draw in any sidings, off the straight track. Just “rough in” the switch at first, until you know exactly where you want it.
Make a simple three dimension drawing (X, Y, Z) to ensure that grades and crossovers are adequate. Begin by locating the portion of your plan which will be the minimum elevation. This can be the lowest part of the table top, the floor or any other arbitrary point you like. The main thing is to make it easy to measure from.
Use your three dimensional drawing to check the clearance at bridges for the train to pass under. Make sure that the grade produced by creating a rise at a bridge is not too steep for your train. A 4 percent grade is about the steepest most models can climb. Leave enough clearance at the bridge for the thickness of the bridge, the height of the cars and the height of the rails and ballasting. In HO scale this requires from 3 to 4 inches of clearance.
Building Your Layout
Once you have drawn a perfect layout, you will still have to build it. During construction, you may adjust for errors in the drawing when you build the layout. You want your drawing to be accurate, but sometime close is good enough!
Some modelers make a full size drawing and trace through the paper or lay the track on top of the paper. This could be impractical for you, if it’s a large layout. You must be careful if you are printing out many pieces of small paper to draw a full size layout. Ensure you are taping them together “to scale.”
When taping paper sections together, you can measure across several pieces of paper to check the overlap at the edges. In other words, if the distance of that yard ladder is 2.52 feet on your layout, measure across all the papers taped together to make sure it’s 2.52 feet in real life while you are taping it all together.
Set up your drawing coordinate system on your bench work.  Simply make an X and Y axis baseline on the bench work. Use one of your main bench edges (or the walls of the room) as the baseline. Draw this in your drawing (if its not there already). Now whenever you use a printout or coordinates to locate something on the bench work, keep “checking in” to the baseline to make sure you haven’t slipped something by a small amount.

Some basic tips for drawing railroad layouts are offered in this article. These guidelines can be used for any scale layout, I’ve used HO because it’s very popular, and the scale I am most familiar with myself. If you are modeling at a different scale, I have several articles outlined the exact details them, in my Tips For Model Railroaders.

The first step in planning your model train layout is to know what scale you are going to work at, and what the overall dimensions of your layout will be. Sketch some rough ideas on paper to get a feel for what you want and how it will work in the amount of space you have.

For more great tips on setting up your model railroad, just fill in your name and email and I’ll send them to you. As an added bonus, you get my detailed report on using DCC to control your trains. 

A good idea is to establish minimum dimensions for your layout such as the minimum curve radii, switch turnout angles and maximum grades. The rolling stock you want to use, and methods of operation, help determine these design elements of your layout. If you are running short trains with just a few cars and engines, then 18″ minimum radius curves will work fine. On the other hand, for larger and longer, you may need curves of 30″ radius or larger (HO scale).

What is the maximum grade you can use?  A 4 or 5 percent grade is rare in prototype railroads but you may need it in your model due to the amount of space you have. If you are planning for one track to cross over another, you must have enough length of track to rise 3″ to 4″ (HO scale) without getting too steep for your models. (Note – prototype railroads rarely go above a 3 percent grade. If you want your model to be completely accurate, then you will also be limited to this amount of grade.)

Model Railroad Clearances

Take extra care when one track comes close to another. Ensure that there is enough clearance for two trains to pass, otherwise the cars will collide and derail. This is especially critical at curves. When the railroad car is on a curve, the ends go over the track width. And, the middle of the car is forced to the inside of the track.

The longer your rolling stock, the more offset you need between curves. You can check this visually by placing your longest and shortest rolling stock on a section of curved track to see the overlap. Set two sections side by side, place your longest locomotive or rolling stock in them, and see for yourself.

Layout Drawing Techniques

A simple way to draw your ideas of a railroad layout is to begin by drawing all the outside dimensions or fixed objects (such as the outline of the room, posts, etc.). Once these fixed objects are located on the drawing, then fill in around them with the track.

Draw in the important scenery, buildings, roads, etc. If you are replicating some real place, work from maps, or perhaps even measurements you took on a scouting visit! Many modelers fine they have to “compress” space, leaving out some of the longer distances, so they can get it all in. That’s fine.

Locate the major curves of your layout next. You know which corners will have a 90 degree turn on the layout. Place a circle in this corner drawn to the radius that you think you need. Place circular arcs in all the corners of the main line. You will connect the circles with your main lines later.

Then select where any switching yards and sidings will be. Using your plan you can try different locations, unless your plan is replicating some real place.

Once the important curves, yards and other objects have been drawn in, begin connecting curves with straight lines. You may want to use broad curves to connect different areas on the layout (instead of straight lines). You can always make adjustments later.

Then draw in any sidings, off the straight track. Just “rough in” the switch at first, until you know exactly where you want it.

Make a simple three dimension drawing (X, Y, Z) to ensure that grades and crossovers are adequate. Begin by locating the portion of your plan which will be the minimum elevation. This can be the lowest part of the table top, the floor or any other arbitrary point you like. The main thing is to make it easy to measure from.

Use your three dimensional drawing to check the clearance at bridges for the train to pass under. Make sure that the grade produced by creating a rise at a bridge is not too steep for your train. A 4 percent grade is about the steepest most models can climb. Leave enough clearance at the bridge for the thickness of the bridge, the height of the cars and the height of the rails and ballasting. In HO scale this requires from 3 to 4 inches of clearance.

Building Your Layout

Once you have drawn a perfect layout, you will still have to build it. During construction, you may adjust for errors in the drawing when you build the layout. You want your drawing to be accurate, but sometime close is good enough!

Some modelers make a full size drawing and trace through the paper or lay the track on top of the paper. This could be impractical for you, if it’s a large layout. You must be careful if you are printing out many pieces of small paper to draw a full size layout. Ensure you are taping them together “to scale.”

When taping paper sections together, you can measure across several pieces of paper to check the overlap at the edges. In other words, if the distance of that yard ladder is 2.52 feet on your layout, measure across all the papers taped together to make sure it’s 2.52 feet in real life while you are taping it all together.

Set up your drawing coordinate system on your bench work.  Simply make an X and Y axis baseline on the bench work. Use one of your main bench edges (or the walls of the room) as the baseline. Draw this in your drawing (if its not there already). Now whenever you use a printout or coordinates to locate something on the bench work, keep “checking in” to the baseline to make sure you haven’t slipped something by a small amount.

Like this article? I’ve also written a two part article about model train benchwork and scenery.

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About Scott

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14 Responses to HO Model Train Layout Guidelines

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