Depot strategies

Depot strategies

Single depot

• All trains on the line return to a single depot at night

Dual depot

• The trains in the line are evenly divided in two groups, A and B
• Group A spends the night in a depot on one end of the line, Group B in the other.

Mixed dual depot

If you want to use nightly depots for very long lines, the total line duration per day usually dictates the service pattern in terms of runs. For example, if your target depot time is between 1am and 4am, that leaves 21 hours to run trains within the day. Trains running a line of 11h or more will only complete one run in the day. This reduces your effective capacity on the line, as a train starting at 4am will "finish the day" in the depot at 15h when there are many passengers around still.

You can fix this using the new "enter " and "exit" stop features in the timetable to break up the line in the middle. Trains will be able to run more hours in the day as a result. This requires a neatly fitting service pattern to ensure all parts of the line are equally covered, and that it fits in a seven day week. This is an example from my Eurostar London - Barcelona line. Half the trains are set up as follows.

In-game example of a mixed-days dual depot.

Group A (half the trains):

• Monday: Start in London Depot, start line in London. Complete run to Barcelona (5h45m). Then complete a full run back and forth (11:30). End in Barcelona Depot.

Tuesday: Start in Barcelona Depot, start line in Barcelona. Complete run to London (5h45m) Then complete a full run back and forth (11:30). End in London Depot.

• Wed: Start in London. [...]. End in Barcelona.
• Thu: Start in Barcelona. [...]. End in London.
• Fri: Start in London. [...]. End in Barcelona.
• Sat: special day, train runs a short day. Starts and ends in Barcelona and completes only a single run back and forth.
• Sun: Start in Barcelona. [...]. End in London.

Group B (other half)

• Same as above but shifted a full day such that the "rest day" is on Sunday.
• In addition, the rest day has to be in the other city (so complete a full run but from the perspective of London)

How to design the appropriate depot strategy for your long distance line

Now that we know about the most complex depot design (the mixed days dual depot, see above), the question is when do we use it?

Here we compare a simple single depot design, as well as a simple dual depot design (at both 'ends' of the line, but no mixed days), and the mixed days dual depot.

In the end the most efficient design depends on three things:

• 1) Line length in hours
• 2) Your desired nightly depo time and its inverse, your "operating hours" during the day
• 3) Interval / number of trains on the line

Given the three of these, the most efficient design is the one that maximises the number of train runs within your operating hours, with the fewest scheduling anomalies. See picture below for a comparison. Key things to note:

Single depot trains operate only in full multiples of the line time. For long lines, some trains will run two laps, some will do just one. Your effective service hours will be constrained late in the day close to the depot. This can be a problem if it's 4pm on a Friday.

Dual depot full multiples only, but doubles the number of trains leaving early enough to run two laps. Generates a scheduling anomalies if not all trains complete the same number of round trips.

Mixed days dual depot is special and forces your trains to operate in 0.5x or 1.5x multiples of the line duration, and similar to dual depot, has two sets of trains leaving early and has potential scheduling anomalies..

Which one do you pick? Well you need to excel through this for your own preferences. For me, it is the the following schedule (22 op hours 4am - 2am, 30m frequencies) depending on the line timing.

• <7h: single depot is fine, constrained operating hours only late in the evening/early morning.
• 7.5h - 8.5h: dual depot; mixed allowed but inefficient.
• >=9h: mixed days dual needed; dual depot has scheduling anomaly

Excel schematic comparing single, dual and mixed days dual depot strategies for a 10 hour (red) and 8-hour (blue) line