Depot strategies
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