Traffic flow in a city is a rich source of information about the city. Cities are being instrumented with video cameras. They can potentially generate continuously large datasets to be processed (big data). This paper reports on our current work to detect traffic flow from an on-line low quality, low frame rate city video camera. The paper details a pipeline of four main steps – background subtraction, scene geometry, car detection, and car counting, and it illustrates results obtained with processing video from a single camera.