One of the key questions asked when it comes to track planning is whether to single track or double track the line. The answer to that dilemma will become apparent when you decide the answers to these 8 questions:

1. Do you have the ability to control two main lines at once?

Running two or more trains on your own is more difficult than you might think, especially when operating a large layout. If you’re operating with DC, you’ll require two power packs, or a double power pack. DCC has made wiring and control much easier, but if you are not paying attention, the trains could derail on a curve, in a tunnel, or onto the floor.

2. Are you prepared for more track maintenance?

I am not trying to discourage you from double tracking, far from it; but it is important to be aware of the ramifications in terms of cost, space, operation, and maintenance. Do you have the time, the energy, and the patience to ensure both mains are kept clean for your trains to run smoothly?

3. Can you afford to have two mainlines?

Double tracking could double (or at least substantially increase) your costs. Apart from the increased space requirements; you will need double the amount of track and roadbed, more ballast, more rail joiners… and the costs of those things can really add up.

4. Do you have enough space to double track?

I touched on space requirements earlier, but the importance of having enough space to double track should not be overlooked. In particular, the curves need to be wide enough and spaced correctly, so that trains don’t side swipe each other and derail. As a guide, take a look at clearances from a prototypical viewpoint.

5. Do you operate enough freight traffic to justify two mains?

In the real world, single track railroads typically have a passing siding where a train can wait for another train to clear. If you’re only going to operate one train, and then maybe 10 to 15 minutes later operate the next one, then a single track is possibly all you require.

6. Is it worth having two mains if there’s minimal rail traffic?

Sometimes it is, especially from an aesthetics point of view. A model railroad can be more visually interesting, and look a little more prototypical by double tracking, or by using a combination of single track and double track. One option is to double track most of the layout and then run a single track over a bridge, through a tunnel, on a tight curve, possibly through a town, or somewhere else where it might be much easier to just have single track. That approach is not uncommon on real railroads, because it can save the railroad money without adversely affecting operational efficiency.

7. What is the length of your longest train?

If you opt to single track your layout and compensate by including passing sidings, then you’ll need to know the length of your longest train before committing. The length of the longest train will determine how long your passing siding needs to be. It should be at least the same length as your longest train.

On real railroads; sidings will generally have a slower speed limit than the main line. Trains on sidings might be restricted to 10 miles per hour. Also, it can be a good idea to position a siding close to a passenger station, rail yard or industry. An industry could operate off a siding without affecting the main line traffic operations.

Now, I could have posed this question earlier, because it is a key factor. However, I wanted to expand on the question so have left it until last.

8. Are you modeling a specific railroad with a specific time and place in mind?

This question is important because in days gone by, double track was often the norm. The same goes for specific railroads. As an example; railroads in Canada, United States and Mexico are classified based around their operating revenue.

In many instances a Class 1 railroad (the biggest) had as many as four mainline, with two in operation for passenger services, and two operating freight services. This minimized delays, because being on a different line the fast freights didn’t need to wait for the slower regular stopping passenger trains.

As a matter of interest, until January 1956 a railroad with revenues of $1 million was classified as a Class 1 railroad. Before 1956, railroads with annual revenues below $100,000 were classified as Class III railroads.

The annual revenue cutoff requirement for railroad classification has increased over the years. Class 1 railroads increased several times from $3 million to $5 million by 1965, to $10 million by 1976, to $50 million in 1978, and in 2011 to $433.2 million. The number of railroads meeting the Class 1 cutoff requirements reduced in number over the years.

Throughout the years there were also other requirements and changes that affected railroad classifications. In 1979 all terminal and switching railroads were re-designated to Class III.

Railroads with increasing revenues were often reluctant to be reclassified, because an upgrading usually meant a corresponding increase in legal and administrative costs. An example was in 1991 when the Wisconsin Central and Montana Rail Link Class II railroads requested the ICC (Interstate Commerce Commission) increase the required minimum revenue requirement from $93.5 million. This was to avoid being re-designated to Class I.

Also, the introduction of CTC (Centralized Traffic Control) changed railroad signal operations. Train crews and local signal operators were no longer responsible for routing decisions. Centralized offices for dispatcher’s were introduced to control train movements were trains moving in opposing directions on the same track use switches and sidings to pass each other.

The widespread use of automobiles, bus, air, and road freight also affected railroad operations. Many rail passenger services ceased to exist as railroads were forced to streamline or downsize operations with single track and passing sidings.

So, numerous changes have impacted rail operation over the decades. This is why, if you want to authentically replicate a real railroad, you will need to know how it operated at a particular point in time.

After giving some thought to how you answered each of the above 8 questions, the decision on whether to single or double track your layout will be an easy decision to make.

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