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Confederation Line - Frequency / Capacity - A Complete Guide


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Thought I would make it a separate thread as it is not only related to opening day.

With the launch in less than a week, I feel like talking about the relation between frequency, capacity, run times and how it affects the operation of the line. See it as a “Transit Line 101”.

A lot of it has been discussed in various threads and in different forms throughout the forum, so I thought one “full explanation” might be worth making. Shane, feel free to use it in any topic you feel it might be related to!


How do we calculate capacity on a transit line?

While there is various measurements of capacity in a transit system, there is commonly two agreed measurements to evaluate the capacity.

  • Passengers per hour, per direction (PPHPD)
  • Capacity per vehicle

While most people are familiar with the second, the first is the most meaningful of the two when you evaluate the throughput of a line, as it considers multiple factors that the first one ignores. If you looked at the capacity of the vehicle only, you would assume more is better, which is a fair assumption as it can move the most people in one trip. However, as many systems have shown, bigger vehicles do not always solve the problems, as they result in generally higher dwell time, and more operational constraints.

Enter the concept of passengers per hour, per direction!

While it still relies on the capacity of the vehicle, it considers the ability of the system to move people between two points, in a given time frame. This is a more realistic measurement of capacity, as it gives a more representative views of how demand and supplies varies in the network. To measure the PPHPD, you generally rely on two or three separate variables:

  • Capacity of the vehicle (P)
  • Trains per hour, per direction (Frequency) (F)
  • Crowding factor (C)

While the two first are obvious, the third one is more of an assessment of how one would expect the network to operate, either at full capacity (C = 1), less than full (C < 1), or overcrowded (C > 1). In the case of the Confederation Line, we can assume C to range between 0 and 1.5 (more on that later). The reason why this variable is important is that transit infrastructures do not always operate at their designed specification, either due to sudden bursts in demand, or the needs around special events. Vehicles are likely to be overcrowded if they fill up after a festival / concert, as people try to go home as soon as possible. On the other hand, some might choose to wait for the next train if it seems “too full” to their liking, resulting in empty space.

To determine a range for C, I used commonly agreed density of people, and compared to the design specification used for the Confederation Line. The city used a measurement at 3 passengers per square metre, resulting in a vehicle capacity of 300 (600 per double trainset). Ideally, “safe crowding” is considered to be in the range of 4-5 passengers per square metre, even though it is possible to stack more. Anything over 5 would be considered “unsafe” and generally is avoided by individuals whenever possible. Since the vehicle is not entirely  standing capacity (120 seated, 180 standing), the increase is not a ratio between the rated capacity and expected crowding: only the standing capacity is affected. If we reached 5.5 passengers per square metre, the crowding factor would be at 1.5 (trains would operate at 1.5 times their rated capacity), which is probably the limit we could / should expect.

Let’s put everything together in a simple formula.

PPHPD = C * P * F

You can basically use this formula for any transit system, and get a comparable point of reference.


So, what is the capacity of the Confederation Line?

The answer varies, as it depends on the time of operation and the acceptable crowding you could expect. Personally, I consider anything over 4 - 4.5 passengers per square metre to be far from ideal, so I will not calculate up to the full C = 1.5. At peak service, the line will have a frequency of 15 trains per hour initially, using 13 double train-sets (therefore a capacity of 600 passengers at C=1)

Crowding Factor = 1

PPHPD = 1 * 600 * 15 = 9000 passengers, per hour, per direction.

Crowding Factor = 1.3

PPHPD = 1.3 * 600 * 15 = 11700 passengers per hour, per direction.

Crowding Factor = 1.5

PPHPD = 1.5 * 600 * 15 = 13500 passengers per hour, per direction.

As you can see, throughput can vary considerably depending on how crowded you are willing to accept your vehicles to be. Of course, too much crowding will likely result in decreased ridership overtime, but it can help illustrate the “peak” output of a system. On paper, given the official capacity figures, the Confederation Line will launch with a capacity of 9,000 PPHPD. In comparison, the transitway is designed with a peak capacity of just over 10,000 PPHPD, a limit imposed by the shared way downtown.

Note that the city is operating the line at launch with 13 double-trains, even though they have the fleet to support 15 double-trains. It is not known if they will be used in situations where extra-capacity is needed, or will be added onto the time-schedule in the future (likely increasing frequency to 16-17 trains per hour)


Did we just replace the Transitway with something that has less capacity?


The important term is peak capacity. In the case of the Confederation Line, we are far from peak capacity, as we have not discussed the two other variables: passenger capacity, and frequency.

Thanks to CBTC, the Confederation Line can operate with trains every 80-90 seconds, giving it a peak frequency of 40 - 45 trains per hour along its alignment. Of course, it would require either additional vehicles, or speed increases along the guideway, an option which is far from likely. Additional vehicles are planned as the line will be expanded through Stage 2 and Stage 3, but also to adjust with Ottawa’s increasing population. This alone would lead to a capacity of (at least) 24,000 PPHPD, at our base crowding factor.

In addition to increasing the frequency, the Citadis Spirit is a flexible design when it comes to capacity. As such, the City could purchase an additional “car” for each trainset, which would increase capacity per vehicle. Alstom rates the “full-length” vehicle at 370 passengers, for a total of 740 per double set. While increasing the length of the vehicle would require a reconfiguration of most stations (underground stations have already been built to meet the added length requirement), it can be combined with the increase in frequency to arrive at an “ultimate” capacity figure of 29,600 PPHPD using our base crowding factor. For reference, the Younge-University Line in Toronto currently operated at 28,500 PPHPD. The difference: we can achieve this with light-rail.

It is really important to mention that this capacity is based on the city’s rather “conservative” 3 passengers per square metre capacity numbers, which is likely to be exceeded. At C=1.3, you’re close to 38,000 PPHPD. I don’t believe you would want to operate this level of crowding for long periods of time, but it it still a “reasonable” expectation.


Will Stage 2 increase capacity on the line?

From the reports that currently exists, I cannot find any reference to capacity increases within the Project Agreement, or at least no meaningful confirmation of it. Unless we adopt bigger trains, or vehicles with more capacity in the same footprint, 29,600 PPHPD is likely the “maximum” capacity we can expect on the Confederation Line without a massive overhaul. It is not expected that the train frequency will increase considerably with Stage 2, though the demand along the alignment will lead to new possibilities in regard to capacity management.

As can be expected, the capacity requirements outside the downtown core will certainly be lower than the central section of the line, due to lower density developments, but also the overall benefit reduction in using public transit for those commutes. As such, the city could interline trains on the alignment, meaning that certain trains would either “short-turn” (stop before the terminus station) or add “gap trains” (train added between two scheduled service in order to increase capacity and reduce crowding) that would dynamically affect capacity due to the different terminus on the Confederation Line (Moodie and Baseline) and the lower demand past Blair station. Trains towards Moodie will be less frequent than those to Baseline, resulting in a lower frequency between Lincoln Fields - Moodie than Lincoln Fields - Baseline. However, as the trains will interline, the frequency in the downtown core will be higher than the two segments mentioned above. Plans call for Blair to remain a short-turn point for many trips, as demand towards Trim will not be high enough to justify all trains to go on the full alignment, reducing costs and the number of empty trips.


What if we reach the maximum capacity?

While it is difficult to imagine Ottawa growing quickly enough to saturate the full capacity of the alignment, there is still some options to increase capacity beyond the 29,600 PPHPD cap discussed above. Below are a few solutions, in what I believe to be the “most probable” to “least likely” option.

  • Increased standing capacity. It can be done by removing seating options, though it is more difficult to do with low-floor trains, as the bogeys still occupy a considerable amount of space in each trainset.
  • Implementation of “Express” trains, which would skip certain stations. This would require the installation of “by-pass” tracks in certain spots, though it remains limited by the dwell time at each station.
  • Implementation of larger vehicles. The tunnel profile would allow for larger train-sets to operate, though it would require the reconfiguration of platforms. As they would need to be further away from the tracks. This would basically mean replacing parts of the fleet.
  • Longer trains. While the Citadis Spirit is not designed to have additional cars added, a third train set could “hypothetically” be added, increasing capacity by another 1/3. Of course, this would result in an entire reconfiguration of the alignment, likely lower frequency, extensive rebuilt of stations and facilities and considerable costs.
  • Convert the Confederation to heavy rail. Without even discussing all the issues that would arise from such a project, operating “traditional metro” vehicles could increase capacity. If similar in vehicle size to Toronto’s Younge-University Line operating in CBTC, a capacity of 36,000 PPHPD or more could be achieved.
  • Build a second east-west line. Probably the option which could add the most capacity, by diverting the traffic elsewhere. The potential Carling alignment with a at-grade LRT could act as a secondary line, reducing pressure on the Confederation Line. Of course, the costs of such a project would likely be prohibitive, and a “last recourse”.

Like mentioned above, it is VERY unlikely such drastic measures will ever be needed in Ottawa, or at least not in the timeframe used to plan those projects. The scale of the work needed to achieve reliable increases in capacity would likely make it more interesting to build a second alignment to spread the pressure.



Hopefully you found this “guide” insightful and it answered a few of your questions! Feel free to let me know if you’d like me to cover more scenarios or consider other elements in a future analysis!

Edited by DavidBellerive
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Two observations:


1) Can we not also move to trainsets that eliminate the centre cabs? In that way we loose the ability to sever trainsets but also increase capacity. 


2) Rather than Carling, I would propose a relief or second east - west alignment that follows Hazeldean / Robertson / Old Richmond / Baseline / Walkley / Innes roads. 

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1 hour ago, Norman Bates said:

Two observations:


1) Can we not also move to trainsets that eliminate the centre cabs? In that way we loose the ability to sever trainsets but also increase capacity. 


2) Rather than Carling, I would propose a relief or second east - west alignment that follows Hazeldean / Robertson / Old Richmond / Baseline / Walkley / Innes roads. 

I thought of your first point as well. Since train sets, it seems, will now be permanently be linked together, the centre cabs are now nothing more than a waste of space. When it is time to order new rolling stock, we could challenge train builders to design an LRT vehicle that is a continuous 120-130 meters (cabs overhang the platforms), similar to the new Montreal Azures or Toronto Rockets. If these manufacturers were able to figure out how to do this with heavy rail, surely they can do the same with light-rail. I believe the Citadis Spirit is currently the longest LRT vehicle ever built: we can inspire the next step. We could also one day switch to full automation, eliminating the cabs completely. This might require platform screen doors since we're running low-floor LRVs. 

As for your second point, if/when the Confederation Line is over capacity, downtown will likely require a relief line, so the chosen route would need to go through the centre of the city somehow.  My alignment of choice would start at Bayshore (transfer to Line 1) down Carling, transfer station at the current Carling Station of Trillium (rename Dow's Lake as part of Stage 2 please) to Lansdowne, up Bank, under Albert, north to Rideau (transfer to Line 1 and possible STO Line), under Rideau and Montreal, turn south to serve La Cité and Blair Station (transfer Line 1) and follow the Cumberland Transitway to Millennium. The line would be fully grade separated, like Confederation, with a mix of under-over and at ground level. Line could be built in three stages (1. Lansdowne to Vanier, 2. complete the inner Greenbelt alignment, 3. Cumberland Transitway).  

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14 hours ago, Corvulpes said:

I'm 50% sure the trains will have trouble fitting 600.

I’m really curious to see how 300 people per vehicle will look like. If it is done with a proper 3 people per square metre, nothing really crazy there, though real life and theory varies considerably sometimes...

As for the points brought up by @J.OT13 and @Norman Bates, point 1 is likely possible. Since each unit provides its own power, the stress on the assembly “wouldn’t” increase as much as adding trailing cars to a pulled locomotive system. Given that each car has its own buggeys, I am not sure how permanent the assembly is, as it can be already extended. I think the complexity comes in the electrical systems and power delivery for the traction motors, though I might be wrong.

For point 2, the overally alignment would indeed need to be downtown, or deserve a specific area of peak demand. Where to put such a line is really one difficult design decision: you don’t want the catchment area to overlap, but at the same time you want to put it where people go to. The problem with Ottawa is that the city is so spread around that destination points are all over. Even if the city was denser, such spread is quite an issue when it comes to deciding where to go first. A multi-stage approach like Norman mentions is probably the most probable.

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