A completely different approach to capture the rhythm of the city can be through image or video capturing. I have been playing around with timelapse techniques. There are a number of tutorials out there, really good ones on DigitalUrban.
Transport networks are quite a simple and steady producer of rhythms. It all relates to a timetable and the frequency of the stops. Here is a clip from a Tube stop in London. Passengers are swiped in and out of the carriages onto the platform in waves.
The journey on the bus gives a similar impression. Here is especially the frequency of the bus stops indicating a rhythm. It is stop motion in the most literal sense of the word.