Circular style neighbourhoods make good transit difficult

Calgary’s obsession with circles

Note: This was first published on Klumpentown on December 17, 2015. It has been edited slightly for clarity.

As someone with a math background and an interest in how cities work, I spend a lot of time thinking about how the geometry of certain neighborhoods affects transit’s ability to be effective. This is not a new idea, Jarrett Walker often discusses the geometry of transit situations in his blog and his book. In this article I hope to convince you that the basic shapes of neighborhoods can drastically change how people choose to move about.

Geometry plays a very fundamental role in city and transport planning, since it defines exactly how space is used. Certain shapes can use space more effectively than others (for example, a circle with a certain circumference takes up more area than a square with the same perimeter), but certain shapes are more aesthetically appealing than others. As we delve into the subject of suburban layout and transit, I am going to discuss shapes from the perspective of their synergy with transportation and transit. I acknowledge that this desire must be balanced with the desire for aesthetics and safety.

Calgary’s Obsession With Circles

In Calgary, we (or at least developers) seem to have a particular affinity to ’round’ suburban neighbourhoods. The basic premise of almost every new neighbourhood design is to construct a wide, circular loop, and attach smaller circular loops to it. Then, pick one or two convenient locations and attach this large loop to the greater city street network. Fill in the rest with houses and the occasional park or shopping centre, and you have yourself a ‘designer community’ in Calgary. There are too many of these communities to list in Calgary, but some good examples include Tuscany, Cranston, Hidden Valley, and Sienna Hills. If you want to add some extra flair, you can consider filling in some of the centre loop with a lake, like Midnapore or Auburn Bay. To really complete the feeling, make sure you name all the streets thematically and confusingly similar, using the neighbourhoods name as inspiration.

The above outline of Calgary neighbourhoods may seem critical, and perhaps that is a reflection of my general disappointment in the originality of people who are designing Calgary’s newest neighbourhoods. The real purpose of the description was to show you that many, many suburban neighbourhoods in Calgary share the same basic shape: a circle, with circles attached. Since I am a theorist at heart, I am going to approximate the typical suburban Calgary neighbourhood with the following shape:

The layout of our neighbourhood is fractal in nature, meaning that if I zoom in to look at a smaller section of the neighbourhood (one of the smaller circles), it looks much the same as the larger one (a circle with some exit roads). For that reason, many of the conclusions we make about the larger neighbourhood as a whole applies to the smaller portions of them, as long as we keep our discussion related to geometry.

The biggest barrier to having a good transit service in such an area is also the biggest barrier to any form of transportation that isn’t a vehicle, and it all comes from an ancient mathematical principle: the shortest distance between two points is a straight line. This is the reason for the appearance of desire lines. In our circular neighbourhood, every single trip you make accessing a bus will involve walking along a curve, which is guaranteed to be longer than the same straight line. This simple principle of geometry is what makes designs like this so car-centric, since when travelling by car the additional distances caused by the curves are much less noticeable.

Another problem comes from the lack of interaction between streets. Placing a bus service in this community would either mean running the bus on half the loop only but allowing the bus to traverse through the neighbourhood, or running the bus on the entire loop but leaving the same way you came in. This stops transit from being a direct service from destination to destination (see Walker’s section on linearity in his ridership post).

There are plenty of arguments made for why these types of neighbourhoods can be considered well or poorly designed, but the we need to think carefully about the basic shapes we are choosing for our neighbourhoods, and what they might mean for the people that live there, the people that visit, and the city as a whole.