5Ks, 10Ks, and marathons are common, but what we need are more shorter distance races on the roads. Call it the "downtown dash" or something and have a day filled with 400m, 800m, 1K, 1500m, and/or mile races. Winners get a $100 gift card to a local store, people who break the course record get a $200 prize, everyone who hits a certain time standard gets a 50% discount for their next race, and all finishers get race shirts.
It would be much cheaper and easier to organize since you wouldn't have to close as many streets as you would for a 10K. You could also play a song that lasts for three minutes and give a 3:00 bumper sticker to anyone who finishes the 1K before the song ends.
Would anyone be interested in running that type of race? If not, why, and if so, shouldn't there be more short distance road races out there?