Learning from Airport Transit

This Calgary-focused post first appeared on Spur.

Believe it or not, waiting for a flight can be a perfect time to study transit operations.

Airports are, in many ways, miniature cities with lots of pedestrians. Passengers, laden down with bags, place a high value on a comfortable shuttle trip between terminals. Travelers are also very uncertainty-averse: not knowing where to go or how long it will take to get there is a huge problem when someone has a flight to catch. These are all things we must be sensitive to when we think about running buses.

On the plus side, they are also places where a lot of the difficult to plan for variables that transit operators face are removed. No mixed traffic. No weather. No stoplights. I like to think of them as semi-controlled laboratories where certain fundamental difficulties become clear.

As part of Calgary’s new international terminal expansion, the airport created what’s called “YYC Link”, essentially a frequent bus service that runs between the four main terminal piers. They are intended to run every couple of minutes (the frequency is not advertised) and hold about 10 people. They run in a dedicated “roadway” and stop a raised station platforms. Pretty much exactly what  a BRT should be.

In my first attempt to use the service I experienced the classic problem faced by frequent, unscheduled bus service: bunching. While I waited, three  pretty much empty buses came by in the opposite direction (roughly every 90 seconds) before a completely full cart pulled up. This gap in service is problematic as a passenger; as I stand there I get nervous as to whether the service is working properly and when a full cart pulls up after some time I decided to just walk. At least I know how long that will take me.

Bus bunching is a very common phenomenon, and it’s a core part of my PhD research. In Calgary, it happens from time to time (especially on routes with frequent buses like the 3) but it’s harder to observe first hand what is happening. In this case, it was clear: a slightly higher than normal amount of passengers decided to show up for this particular bus, and so it had to wait longer to load them. This in turn left a larger gap in time between it and the bus in front, and so more passengers were waiting at the next stop, causing a further delay. For the bus behind this one, it was probably a breezy ride, and it likely caught up right away.

Airports are probably not used to thinking about transit operations and some of the pitfalls that can come from letting the service run without some form of control (I suggest they have a look at something like this paper). It’s interesting to see the phenomenon so clearly.

As a final thought, I also realized that with this new service, a whole lot more of the airport opened up to me. I could, if I had an hour to kill, easily head over to another terminal and visit a preferred restaurant. It starkly demonstrated to me the freedom that useful transit can provide for people, in an airport or a city.

So next time you’re waiting for a flight at YYC, sit for a few minutes and watch the buses go by. You might come to appreciate the bigger ones outside more.

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