Moving traffic is a useful subject for testing a lens or practicing focus and playing with shutter speeds. In February I shot a campaign for a football club. The brief was to get close-ups of fans and players over two games. The crowd pictures needed a 600mm lens with a 2x extender which is less than ideal for fast-moving action in low light.
I decided to practice at a couple of evening rush hours. The autofocus worked well and the image quality at high ASA (12800!) was surprisingly good, especially comparing it to 800ASA film pushed two stops at a night game in the olden days.