Basic layout building blocks

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Basic layout building blocks

In the beginning there was the train set - an engine, a few cars, a caboose, and an oval of track. If you are reading this, the oval was not enough and you want more. Other sections of the primer such as Givens and Druthers will guide you on what to model. This section will show you the basic track elements and how to put them together to achieve your goals.

Whether you are building a small portable layout or the transportation system of a lifetime, the basic building blocks are the same. Obviously, a large layout will be larger and more complex, but the principles are the same. A strict prototype modeler will selectively compress the prototype's building blocks for the visible portion of the layout but not for hidden tracks or staging.

How Does the Prototype Operate?

In real life, a railroad moves a car from one place to another. In fact, most railroads are built to connect two locations. Except for very special cases such as fresh produce or passenger trains, a car going from one location to another is put in trains that are constantly broken apart and reformed as they pass through interchange points. Thus, a car may:

  • start at an industrial siding,
  • be moved by a local switching run to a local freight yard,
  • be switched onto a yard track with other cars to be picked up by a peddler freight and taken to a district yard,
  • be switched to a long haul freight to the next district yard,
  • be switched at several other district yards until it arrives it is switched to another peddler freight to a local yard and then to another industrial siding.

An example might be a boxcar of lumber from a mill in Oregon being shipped to a furniture factory in North Carolina. The car might travel on 5 or more railroads and be switched in and out of 25 or more consists. Obviously we cannot model all 5 railroads and 25 separate trains across 3,000 miles. Instead, we may produce only a part of it.

We generally specify top-down what we want our railroad to do. We then build the actual track arrangements bottom-up to fit the goals. For example, we top-down specify a yard at a particular location, but bottom-up start with the mainline through the yard and add tracks to fit the terrain and space available.

Building Block Levels

We will first define the levels and then discuss them in detail. At the highest level, layouts are combinations of Complete Blocks. They are complete in the sense that a layout may be just one complete block. There are two types: Continuous Loops and End-to-End. Middle level blocks are called Element Blocks. These blocks are sections of a layout that are seen as one visual or logical piece. There are four types: Layout Design Elements, Hidden Tracks, Return Loops, Staging, and Helixes. The lowest level blocks are Basic Blocks, which are common structures for all of the element blocks. There are many types depending on the purpose, era, and emphasis of the designer. The ones we will discuss here are the most common ones: Passing Tracks, Runaround Tracks, Industrial Sidings, Interchange, Passenger Facility, Freight Stations, Team Tracks, Freight Yards, Engine and Repair Facilities.

Complete Blocks

Most small model railroads are either loops or end-to-end, but larger layouts may be combinations or multiples of either or both, connected or disjointed.

While most railroads do not operate loops, they are favorites for beginning model railroaders and those who favor running trains over operating because the trains can be started and will run without attention. Prototype model railroaders tend to favor end-to-end because that is how the prototype actually was. However, judicious use of hidden staging can make a loop look like an end-to-end or give an end-to-end continuous running capability.

Loops need not be simple ovals. Some examples from John Armstrong's "Track Plannning for Realistic Operation", Third Edition, Kalmbach, 1998, p. 100 are a Figure 8, Dogbone, Folded Dogbone, and Twice-around. By hiding part of the loop, the loop can be made to appear as a "sincere" end-to-end layout that models just a part of a prototype between two points. The hidden part can be a double-ended staging yard for operations.

End-to-end models a beginning and an end. An oversimplification of the operating concept is that each train is made up at an end and travels across the layout to the other end where it is broken down. The simplest example of an end-to-end is a switching layout, which need be no larger than 1' x 4' in HO scale. A common use for end-to-end on a layout is a branch line, which begins at an interchange, typically with a mainline, and crosses a significant space to an endpoint, typically a town, a major industry, or another interchange. A neat example is a narrow gauge logging shortline hauling logs from the trees to a sawmill, then a branchline hauling the lumber from the sawmill town to a nearby larger town and an interchange with the mainline. The Cass Railroad in West Virginia is a good example.

End-to-end can extend to continuous running by adding a return loop somewhere near or at each end, or by connecting the ends to make a loop. Element Blocks Element blocks are major subsections of layouts that have a unifying purpose or theme. Tony Koester (Model Railroad Planning 1995, Kalmbach ) coined the term Layout Design Element to describe a specific and interesting portion of a real railroad that can be modeled fairly accurately. These have also been called "Dominos" by David Barrow (Model Railroad Planning, 1997). In a general building block context, I have extended the concept to be a portion of a model railroad that is thought of as a single scene. It may be a small as a single siding or a whole town but the view will think of it as one unit.

Significant model railroad elements are also included as element blocks. They are Hidden Tracks, Return Loops, Staging, and Helixes. Hidden tracks disappear and do something that the viewer cannot see. The most overt is a short tunnel where it is obvious where the train will reappear. Really tricky are loads-in, empties-out where the hidden tracks connect a coal mine with a power station. See "Modeling the Clinchfield Railroad in N Scale", Kalmbach, 1990, for a good example.

Another good use of hidden tracks is hidden staging. Whether you are a runner or an operator, having trains already made up and ready to run is important. Hidden staging allows you to successfully pretend that you are modeling the point A to point B portion of a much larger railroad. Things happen offstage in staging that allow you to make the illusion look both realistic and appealing.

Return loops exit from a point in one direction and reappear traveling in the opposite direction. A good place for them is at the end of a end-to-end portion of your layout to allow for continuous running rather than having to use a turntable or wye.

Helixes raise the height of the track in a short linear distance and are particularly useful for getting between decks in a multi-deck design. A helix is basically a set of connected concentric circles where each loop of the track is just above the previous level with just enough raise in height to clear the next lower layer, generally 4" in HO and 2" in N. Helixes are not simple to build but are a design compromise when needed. Basic Blocks Basic blocks are the most difficult to describe in detail here because they are so specific to the givens and druthers of a layout. Real railroads built passing tracks so multiple trains can run at the same time in both directions with minimal delay. Thus, a train with a lower priority will take to a passing track to allow a superior train to pass it. Building passing tracks into a model railroad makes running more than one train interesting.

Runaround tracks look like passing tracks but allow an engine to go the other end of a train to perform switching moves such as servicing an industrial track that faces the "wrong" direction.

Industrial sidings were the life blood of traditional railroading when an industry depending on a railroad to both deliver the raw materials and deliver their finished product. Their use has lessened with intermodals and trucks on modern railroads. The simplest sidings are just a turnout leading to the side of an industry. A model railroad wants several industrial sidings to give it a reason for existing.

Interchanges allow different railroads or branches on the same railroad to forward a car toward its destination. The simplest may be just a single passing siding between a branch line and a mainline. The mainline train leaves cars on the siding for destinations on the branchline and the trains of the branch pick up those cars and drop off return cars from the branch to the mainline. Large cities may have entire railroads devoted to nothing but exchanging cars from the several railroads that lead in and out of the city.

An important element for some models is a passenger facility that can include both a passenger station with complex tracks and support functions. There have been whole layouts that are one big passenger layout design element. At a minimum, a rural passenger should include a station on a siding so passenger trains can layover.

Freight stations have less importance in modern railroading with its emphasis on long haul intermodal. However, many cities in the classic era of railroading were almost wholly dependent on railroads for all consumer goods, both in and out. Railroads handled less-than-car-load freight and were the traditional equivalent of FedEx or UPS. Railroad freight stations were where you picked up the package from aunt Mary or shipped your product when your company was too small to have its own industrial siding coming to your door.

Team tracks are usually little more than a platform beside a siding where less-than-carload freight was handled and are adjuncts of freight stations. Practically every small town once had a team track, even if it did not have a station.

Freight yards were large interchanges where incoming trains were broken down and reassembled into new trains. In classic railroading, steam engines could go about 100 miles between servicing and towns sprung up to provide these engine service facilities. This was also a good place for a district yard where cars for points within that district were added and removed from through trains. Incoming cars were taken off and put on a classification track for its outbound train.

The design of yards is very complex. A yard is more then just classification tracks. They could have all or some of the below:

  • yard leads dedicated to the switching engines to add and remove cars from the classification tracks,
  • arrival and departure tracks were incoming engines left their trains and outgoing engines picked theirs up,
  • repair in place (RIP) tracks where minor repairs such as faulty breaks were taken care of,
  • engine service leads and engine service facilities such as turntables, roundhouses, water, coal, oil, ash, etc.,
  • cleaning track where engines and cars were washed as necessary (cars had to be washed frequently before and after carrying products),
  • icing track for keeping reefers cool
  • stock exercise track (cattle could be transported only a short distance before being fed, watered and exercised),
  • scale track to weigh bulk shipment cars,
  • caboose track for storage between uses,
  • runaround and thoroughfare tracks to allow engines to move within the yard,
  • house tracks (if near station) where switch engines wait between assignments,
  • intermodal load and unload facilities, and
  • team tracks to off load less-than-carload shipments.

See the the primer entry on Yards--freight and passenger for a more detailed discussion of Yards.


There are many pieces to a layout puzzle. We have listed many of the most common. Your prototype, era, interests, and givens and druthers may come up with new elements or significant variations of the ones listed. The main thing to keep in mind is to design your layout so that the combination of the elements rings true.

About this content:
Original author: Tom Reid. Last revised in August, 1999.
This LDSIG article is ©1999 by Tom Reid (email).
Questions/comments may be posted in the discussion tab.

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