I volunteered at a race in Vancouver called "Probably A Bad Idea". It was a fixed only, miss-and-out/ devil take the hindmost race on a tight, winding figure 8 (i think) loop in Gastown, with moderate car traffic and the odd pedestrian. Sounds sketchy, hence the name. But the organizers were really good about making it safe. There were volunteers on every corner who would let the riders know about upcoming hazards, as well as letting cars and peds know when a big pack of cyclists was about to come bombing around the corner. And, helmets were mandatory. The race went awesome and if anything the increased safety gave everyone the confidence to go faster and harder.