Improving LRT Service: More Trains, or Longer Trains?

For a city that likes to drive, Calgary’s light rail transit (LRT) – the CTrain certainly gets a lot of heavy use, especially during peak period. This is largely in part due to Calgary’s high downtown parking rates and relatively poor road access to the core, but the steady increase in ridership is thanks to the lengthening of the network and an addition of a West LRT arm. These extensions increase the level of service for passengers who did not have LRT service before, but it actually makes transit worse for the passengers who were already using it. All else being equal. larger service area means larger demand, and therefore significantly more crowded trains.

This rising LRT use is great, but it doesn’t just come at the cost of extending the network and adding the appropriate number of trains and drivers to keep the same service frequency as before. The crowding increases on trains, and believe it or not this can have a profound effect on the experience of the commuter1,2. There is a great risk of losing ridership from passengers closer to the downtown core, who are now experiencing a more crowded train and may be driven away because of this. As these people leave, of course, more space opens up for the new passengers, and the whole things settles into a sort of equilibrium.

From a pure business perspective as a transit agency, those original shorter-distance commuters are more valuable, especially in Calgary’s situation where every passenger is paying the same fare regardless of the distance they travel; those original commuters are paying more to be transported per kilometer. From this perspective a commuter who boards at the end of the line is less valuable than someone who boards for only a couple of stops. This is a notion that doesn’t sit well with a lot of transit agencies, and is certainly not something you want to market as  business strategy, so a position of “everyone is equal” is adopted for those kinds of things, in the spirit of transit offering access to everyone.

There are ways to keep both the new and old riders happy, however. You can either increase the frequency of the trains, or increase the length of the trains. Both of these increase the “seats per hour” that pass a particular point along the route, so it would seem at first glance that both solutions carry equal weight. As you may have already guessed, there are trade-offs to both of them. To continue encouraging transit use, we’ll have to make a decision: trains more often, or longer trains?

Increasing frequency (or decreasing headway) of trains is often a first line of attack. To a certain point, you run trains closer and closer together until you have accommodated what additional capacity you might have. This has the added benefit of improving the mobility of the whole network, since the smaller the headways, the closer transit can approximate the freedom provided by the automobile. Capital costs are relatively low, you just need to buy some more train cars. You also have to hire drivers, and in a country like Canada, where wages are relatively high this can be a huge factor in the service. Of course, we already know how to model what the best headway should be.

The other option is to just make trains longer, something that is relatively unique to trains (you can increase bus length, but that requires purchasing an entire new bus). This also increases the space available, and does not require any drivers. Capital costs are higher, since in addition to purchasing train cars, you also need to extend the platform length at each of the stations. The larger the network, the more costly the expansion. This option is better for smaller networks, or (as in Calgary’s case) where you plan ahead before expanding your network to build larger stations ahead of time.

In reality, a shorter headway usually wins out as a first way to increase service, since demand is so high that the waiting costs compound with the crowding costs to demand bigger capacity and more frequent service3. Another way of thinking about it is this: with shorter hedways, the original passengers are happy (improved capacity), and new short-haul (more valuable?) passengers may be attracted due to the more frequent service. There is a strict limitation on this though, usually due to the signal infrastructure and safety problems. In Calgary, the above ground corridor in the downtown makes it impractical to run trains with less than 5 minute headways (I still think it’s better than putting it underground), so there is little choice but to lengthen the trains. Calgary Transit is doing just that, planning to start running 4 car trains in late 2015. Once you’ve shortened headways, it becomes another problem to balance operating/capital costs of increased train length with the unpleasantness of crowding on trains. In fact, there may be more research to follow3.


 

References

  1. Evans, G. W., & Wener, R. E. (2007). Crowding and personal space invasion on the train: Please don’t make me sit in the middle. Journal of Environmental Psychology, 27, 90–94.
  2. Hirsch, L., & Thompson, K. (2011). I can sit but I’d rather stand: Commuter’s experience of crowdedness and fellow passenger behaviour in carriages on Australian metropolitan trains. Australian Transport Research Forum 2011 Proceedings, 34(0245), 1–15.
  3. Klumpenhouwer, W. (2014). Cost-of-crowding model for LRT train and platform length.

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