Joe Fugate's HO Siskiyou Line Model Railroad

LAYOUT COMPARISON USING STATISTICS
The case for better analysis of layout plans

You've just located two published track plans that both fit the space you have, and they're both for one of your favorite roads. But, you wonder, which plan will better meet your operating expectations? Even though you like the aesthetics of both designs, which will take less money and time to build?

Is there an easy way to find concrete answers to these questions BEFORE you cut the first stick of lumber? The answer is a resounding "Yes"! With a calculator, ruler, and a scale track plan, you can get solid answers to these questions with an hour or two of analysis.

THE BASIC STATS

Let's look at the specific statistics and how to compute them.

ROOM AREA (sq ft): Calculate the layout room's square footage. If your room is much larger than the layout -- such as a 4x8 layout in a large family room -- then only include a reasonable amount of access space around the layout -- don't include all that extra room space. For instance, with a 4x8 layout in a large recreation room, you might add a 2 foot aisle all around the layout. This means the total "room area" for a 4 x 8 layout might be 8 x 12, or 96 square feet.

This stat tells us the approximate space requirement for a given layout, regardless of its shape. This is a clue that two differently shaped layouts could be altered to fit into each other's space. This won't always work, but at least it's worth exploring.

LAYOUT AREA (sq ft): Calculate the total area taken up by just the layout "tabletop" itself. This does not include aisle space. For the 4x8 layout, this will be 32 square feet.

This stat allows us to see just how much layout we really have, and is a valuable design statistic since it allows us to directly derive the amount of benchwork and scenery the layout needs. By comparing the room area with the layout area, we can ascertain how well the layout design fills its space. For instance, the 4x8 layout's space usage is 32/96, or 33%. Most along-the-wall designs have an space usage of 50% or more, which shows us the 4x8 layout doesn't fill the space nearly as well as an along-the-wall design.

Filling the space isn't the only issue, since we could build a wall-to-wall table and fill the space 100%. Access, however, would be abysmal. As long as good access is maintained, this stat is useful --but it must be viewed in context with your other design needs and goals.

NUMBER OF TURNOUTS: To compute this stat, just count the number of turnouts on the track plan. Also count a crossing as a turnout, and count a single slip switch or three-way turnout as TWO turnouts. Count a double slip switch as THREE turnouts.

This stat is a good indicator of trackwork complexity, which tells us many useful insights. Given that the most costly trackwork is a turnout, the most maintenance intensive trackwork is a turnout, and the most interesting trackwork operationally is a turnout -- depending on what trade-offs we're after (less cost, less maintenance, more interesting operation), more or fewer turnouts may be preferable. Combining this stat with the next one on total trackage gives us enough information to do a rough estimate of the trackwork and wiring costs for the layout.

TOTAL TRACK (ft/cars): Determine how many feet of track are on the track plan by measuring it. Record the result as both total footage and as the equivalent number of 40 foot cars. Using 40-foot cars in the stats allows us to directly compare track plans across scales. To determine the 40 foot cars equivalent for a track plan, use the appropriate factor from the following table:

Car Lengths per foot

For instance, if an S scale layout has a total track of 211 feet, then the cars equivalent will be 316 cars (211 x 1.5). Drop any fractions -- don't round. It's best to deal only with whole car lengths and lean to the conservative side when computing car capacities.

This stat, in combination with the other track stats below, tells us much about the operational possibilities of the track plan.

MAINLINE TRACK (cars): Measure the length of the mainline in feet and convert it to the cars equivalent. The main route of a branchline is also considered mainline for the purposes of computing this statistic. Also, one track running through any visible yard and any staging yard needs to be designated as part of the "main" and included in this total.

As an exception, the offstage portion of a single track that runs into staging to be used as car storage/interchange is not "mainline" but instead is "staging" (see below).

From this stat, we get a sense of how much "mainline" running is available on the layout.

PASSING TRACK (cars): Measure the length of each passing siding in feet and add them together. Do not count track where the main would be fouled if cars were on the siding. That short chunk of track from the turnout points to the clearance point is connecting track (see below), not passing track. Convert this figure to the cars equivalent.

This stat helps us determine mainline traffic levels (more on this later).

STORAGE TRACK (cars): Storage track is the amount of track in industrial spurs and yard storage (but don't include staging, that's a separate category below). Measure and total up the length of track in this category, and convert it to the cars equivalent. Like passing track, don't count track in this total where the connecting track would be fouled. Remember one track running through any yard was counted in the mainline total and is not to be included in this total.

STAGING TRACK (cars): Measure the total amount of track used to stage trains and compute the cars equivalent. Again, don't count track where the connecting track would be fouled. Don't forget that one track running through any staging area was counted in the mainline total and is not to be included in this total.

Remember the one exception -- the offstage portion of a single-track car storage/interchange track is "staging", not "mainline".

SERVICE TRACK (cars): Service track is loco storage, servicing, turntable, turntable leads, and so on. The rule of thumb is: if the track is used to store cars, then it is storage (or staging if it is "offstage"), if it is used to store locos and is traversed primarily by only locos, then it is loco service track. Measure the total amount of track used to service locos and compute the cars equivalent.

CONNECTING TRACK (cars): Connecting track is what's left. Compute it as:

Connecting track = total track - mainline - passing - storage - staging - service

Connecting track is what allows us to make up and break down trains, and to maneuver cars from the main to industrial spurs and yard tracks. It turns out this track is ESSENTIAL to getting a layout that can move a LOT of cars.

PASSING SIDINGS: Record the number of passing sidings.

PASSING TRAIN LENGTH (Cars): Write this stat as three values separated by slashes -- longest/average/shortest. Longest is the length of your longest passing siding in cars. Average is the length of an average passing siding in cars, computed as: passing track / number of passing sidings. Shortest is the length of your shortest passing siding in cars.

STAGING TRACKS: Record the number of staging tracks.

STAGING TRAIN LENGTH (Cars): Write this stat as three values separated by slashes -- longest/average/shortest. Longest is the length of your longest staging track in cars. Average is the length an average staging track in cars, computed as: staging track / number of staging tracks. Shortest is the length of your shortest staging track in cars.

Ideally, staging train lengths should more or less equal the corresponding passing train lengths. Significantly smaller staging train lengths mean extra switching will be involved in getting a "full length" train into or out of staging. Larger staging train lengths mean full length opposing trains from staging will clog the main. The longer of passing or staging train length should rule in determining typical long train length. The shorter of passing or staging train lengths should rule in determining typical average and short train lengths.

You may notice that staging tracks and passing tracks appear somewhat interchangeable in these formulas. This either/or use of staging and passing sidings reflects an operating session reality (one that was actually exploited by Tony Koester on his AM, by the way) where the layout's staging can be viewed as "virtual passing sidings". For example, the dispatcher could set up a "meet" between opposing trains to occur offstage. To do such a "meet", one train exits the layout into staging, after which a different train enters the layout -- as if a meet had just taken place in an offstage passing siding. If some of the passing sidings on the layout are rather short, this can be a useful technique for arranging meets between longer trains.

OPERATION POTENTIAL STATS

From the basic stats, we can quickly estimate the layout's operating potential. Way back in June 1968, MR published "Layout plans by formula", written by Roy F. Dohn. Mr. Dohn described how to estimate the operating potential of a track plan using some clever formulas he developed by working backwards from actual operating model railroads. Using his formulas as a starting point, I have developed an updated set of formulas.

MAXIMUM NUMBER OF CARS: A layout can only hold so many cars before you become unable to move because even the destinations are full. This upper limit seems to be around 80% of the total capacity for stationary cars, so we can compute this as: 80% of (storage + staging + passing/2).

To allow for more cars on the layout, increase the amount of storage and/or staging track, or to a lesser degree, add some passing track capacity. Generally, passing trackage is not intended to be used as permanent storage, so to indicate that some passing siding capacity could be used as short-term storage, a factor of one half is suggested in the formula.

NUMBER OF CARS MOVED: The number of cars moved in a typical operating cycle can be computed as: 40% of (staging x 2 + passing + connecting). To increase the number of cars moved, we need to increase some combination of staging, passing, or connecting trackage. Notice staging is particularly effective in increasing the number of cars moved, since for every train that leaves staging, another can move in to replace it, meaning TWICE the cars can be moved (if they are available elsewhere on the layout). In effect, staging acts as both connecting track and passing track -- thus serving double duty.

Another thing we can do to increase cars moved is stop using some track for storage, and designate it instead to be either staging, passing (if trains can legitimately "pass" on this trackage), or leaving it undesignated and always free of stored cars (so by default it becomes connecting track).

TRAINS: We can divide the number of cars moved by our average train length to arrive at the average number of trains we can expect in a typical operating cycle. Average train length is the smaller of average passing train length or average staging train length.

One operating cycle is defined as running the layout in a realistic manner until the trains you run begin to repeat. Ordinarily this will be one "24 hour" day according to the modeled train schedule. Depending on our fast clock ratio, the experience of our crew, the reliability of our equipment, the length of a typical run, and the level of detail to which we simulate prototype operating practices, the actual time it takes to complete one cycle could vary from one hour to dozens of hours. Three hours is probably a good typical cycle, however.

DISPATCHING THRESHOLD: Compute as (3 x shortest passing siding + 2 x average passing siding + longest passing siding) / 6. Two opposing trains of this size or larger will tend to create a dispatching bottleneck because they cannot easily pass each other except at select sidings. If you want to ease the dispatcher's workload, keep the typical train length at or under this size.

If you want the dispatcher to more easily manage longer trains, then lengthen your passing sidings. The best way to increase this threshold is to lengthen your SHORTEST passing sidings first. Of course, you need to keep the length of your staging tracks in sync with passing siding lengths as explained above under the train length stats.

Another less obvious tactic to improve this stat (if your passing sidings are smaller than your staging tracks) is to declare very short passing sidings to be switching runaround tracks only (and thus connecting track instead of passing track), thereby removing them from routine consideration as locations where the dispatcher might arrange meets. This tactic also has the effect of increasing the number of cars moved since it creates more connecting trackage.

EXAMPLES:

HO SP Siskiyou Line (Joe Fugate)

The Siskiyou Line was designed for long trains in the spirit of the prototype SP, so the average length train is 30-33 cars. Notice the variation between the shorter and longer passing sidings is enough that most trains will exceed the dispatching threshold of 22 car trains. Dispatching this railroad can become a challenge since two average length or longer trains will only be able to meet at a few select passing sidings. One gets faint hearted, however, realizing 500-800+ cars will be needed for full operation! What have I gotten myself into?

Stats for a couple of 4x8 beginner layouts in recent issues of MR.

HO Soo Red Wing Division (12/94 MR)

The most notable problem with this design is the staging train lengths are SIGNIFICANTLY smaller than the passing train lengths. Considerable switching will be necessary to get trains into and out of staging --which could be good or bad, depending on how much you enjoy switching as opposed to mainline running.

HO Alkali Central (12/95 MR)

This layout has a serious problem: no passing sidings. Notice the dispatching threshold stat tells us immediately that ANY cars on the main OWN the main, period. Who needs a dispatcher when you can run only one train at a time? This is definitely a beginner's layout and not one for anyone interested in advancing into realistic multitrain operation. The Soo Red Wing Division is a much better layout for a beginner with future growth in mind since its operation potential is far greater.

PUBLISHING STATS ON TRACK PLANS

It is also possible to present these stats in a summary form as follows:

HO SP Siskiyou Line (Joe Fugate)

HO Soo Red Wing Division (12/94 MR)

HO Alkali Central (12/95 MR)

I recommend the summary form in published track plans.

ESTIMATING BUILDING TIME AND COST

From the basic stats, we can do rough estimates of building time and cost. These values are somewhat subjective, especially the building time. The time and cost estimates depend a lot on individual tastes, working style, and experience. The best way for you to get a good idea of estimates that work for you is to do some pilot projects. Join a modular club and build a module. Build a test diorama. While you are building, track your costs and time durations closely.

BENCHWORK: We can multiply the layout area stat by a cost or time per square foot of benchwork to get the approximate cost or time to build the plan's benchwork.

TRACKWORK: We can multiply the total track stat by the cost or time per foot of track to determine the basic trackwork cost/time. Add in the cost or time factor per turnout to get the approximate trackwork cost/time.

ELECTRICAL: The electrical part of a layout can be estimated from the total track stat, since powering the track and operating the turnouts is what the wiring is all about. If you are using DCC, just add in the cost of your basic system, and factor in throttle bus wiring based on the mainline track stat, since the bus can follow the mainline (more or less). Cab control wiring can be estimated from the number of electrical blocks needed, with the average length of wire from a central control panel to the block being 1/2 the length of the mainline. Local panels will need to have the wire length estimated on a case-by-case basis.

SCENERY: Using the layout area stat, we can multiply this area by the cost/time of basic scenery (minus structures or details) per square foot to get a basic scenery cost/time.

STRUCTURES AND DETAILS: Structure and detail cost/time are harder to judge since they are not strictly by the square foot. However, we can work with a larger area, say every 10 square feet -- and it is possible, with a little thought, to come up with a rating system to categorize various regions of the layout in one of four categories: wild (foliage only, few extra details), rural (foliage with some small structures and details), town (mostly small structures, roads, and details), city (mostly large structures, roads, and details). Then you rate every 10 square feet as to its category, using the appropriate time/cost factors for that section.

ROLLING STOCK: The number of cars stat can be used to estimate the total cost of rolling stock to populate the layout.

LOCOMOTIVES: The number of cars moved stat can be used to estimate the number of trains in a typical operating cycle. From this and the typical power lashups used to power a train, you can estimate the number of locomotives used in a operating session (this assumes minimal reuse of power, which may not be the case). Once you know the number of locomotives you'll need, you can estimate their total cost.

CONCLUSION

As you can see, with these extra few stats, we can truly PLAN a layout, whether big or small. And we can finally compare layouts quickly in a meaningful way -- and appreciate more than just their good looks.

LAYOUT DESIGN FORMULAS SUMMARY

ROOM AREA (sq ft): Gives approximate space requirement for layout.

LAYOUT AREA (sq ft): Shows how much layout we really have.

TRACK COMPLEXITY: Turnout/crossing = 1, Single slip = 3, Double slip = 5
  Tells us level of cost/maintenance (bad), operational flexibility (good)

TOTAL TRACK (ft/cars): Determine total feet of track. Convert to cars:

Car Lengths per foot

MAINLINE TRACK (cars): Measure the length of the mainline. Tell us how much "mainline" running is available on the layout.

PASSING TRACK (cars): Total length of all passing sidings. Do not count track where the main would be fouled. Helps determine traffic levels.

STORAGE TRACK (cars): Total track in industrial spurs and yard storage (don't include staging).

STAGING TRACK (cars): Total track used to stage trains.

SERVICE TRACK (cars): Total track used for loco storage, servicing, turntable, turntable leads, and so on.

CONNECTING TRACK (cars): What's left. Compute it as: total track - mainline - passing - storage - staging - service. Connecting track is ESSENTIAL to getting a layout that can move a LOT of cars.

PASSING SIDINGS: Record number of passing sidings and their length as three values separated by slashes -- longest/average/shortest. Compute average as: passing track total / number of passing sidings.

STAGING TRACKS: Record number of staging tracks and their length as -- longest/average/shortest. Staging train lengths should more or less equal the corresponding passing train lengths. Notice that staging tracks and passing tracks are somewhat interchangeable in these formulas. The dispatcher could set up a "meet" between opposing trains to occur offstage, for instance.

MAX CARS: 80% of (storage + staging + passing/2)

CARS MOVED: 40% of (staging x 2 + passing + connecting)

TRAINS: Divide cars moved by average train length. Average train length is smaller of average passing train length or average staging train length.

DISPATCHING THRESHOLD: Compute as (3 x shortest passing siding + 2 x average passing siding + longest passing siding) / 6. Two opposing trains of this size or larger will tend to create a dispatching bottleneck because they cannot easily pass each other except at select sidings.

Page last updated on December 7, 2004
E-mail:  siskiyou@railfan.net