Every year Lake Worth, FL has a street painting festival fashioned after one held somewhere in Italy. They block off a main street and adjacent side streets downtown and mark off 400 "canvas" areas on the pavement. "Canvases" range from 2' x 3' up to 12' x 12' I think. They have a featured artist area for professionals. Pastels are provided to each artist, too, I believe. People sign up a year in advance and there is usually a waiting list.
It's a whole weekend festival (including food and entertainment) and as you'll see from the website ( http://www.streetpaintingfestival.com/ ), we draw 100,000 visitors over the weekend. Come Sunday night, the streets are reopened and the artwork lasts until it rains or tires wear it off.