Mapping Three Buses at Once

You can wait ages for a bus and then three will turn up all at once.

The phenomenon of bus bunching effects public transit systems around the world. Bus timetables are usually scheduled so that buses on the same route are evenly spaced. Unfortunately in reality passengers often end up waiting ages for a bus, which eventually turns up late and overcrowded - followed closely by one or two other near-empty buses. This is bus bunching.

There are many explanations as to why bus bunching might occur. But before exploring why bus bunching occurs perhaps we should look first at where and when bunching occurs. Pittsburgh's Bus Bunching does exactly this. It uses real-world bus tracking data from Pittsburgh to visualize how bus bunching happens on the city's bus network.

Pittsburgh Bus Bunching uses Carto's Torque library to create an animated map visualization of the city's buses on routes 61, 71, P1 and G2 during March 2016. Press play on the map and you can view an animated heatmap showing the spatial frequency of bunching in Pittsburgh. The map reveals that Oakland, and the intersection of Murray and Forbes in Squirrel Hill are areas where bus bunching appears to occur frequently.

Now that we've identified where the problem occurs all we need to do is work out why ...