To compel drivers to obey posted speed limits, traffic authorities generally wield but one stick: the law book. However, a San Francisco father of three says he believes that if motorists were given positive incentives to check their speed, they would not only do so, but would have fun doing it.

Earlier this year, Kevin Richardson, the San Francisco father, won a contest devised by the Swedish advertising firm DDB Stockholm for Volkswagen Sweden, whereby an open invitation was extended to submit ideas that made seemingly baleful social challenges — environmental protection, speed-limit adherence, boosting public transportation ridership — enjoyable.

The project, called the Fun Theory, yielded concepts that were enacted in and around Stockholm. Short films documenting the projects went viral: a DDB-produced video depicting the Piano Staircase, in which metro riders’ footfalls triggered tones as they exited and entered the station, has more than 600,000 YouTube views.

Mr. Richardson’s winning idea is comparably low on novelty but high on behavioral science. Leveraging traffic-camera and speed-capture technologies, his Speed Camera Lottery device would photograph all drivers passing beneath it. A portion of the subsequent fines levied against speeders would be pooled in a lottery, with a random winner periodically drawn from the group of speed-limit adherents.

The concept’s Stockholm demo, which concluded in November, produced compelling results. According to Volkswagen, average speed before the installation of the Speed Camera Lottery sign on a multilane street was 32 kilometers an hour. That figure dropped to 25 kilometers an hour during a three-day test, despite the device’s inability to issue financial penalties.

Mr. Richardson, a producer for Nickelodeon’s games division, says that traffic law enforcement’s emphasis on punishment, not reward, is outmoded. “Thinking of all the interesting ways we can penalize a few bad or distracted apples is a mis-distribution of energy and attention,” he said in an e-mail.

Volkswagen Sweden did not alert Mr. Richardson of his success until the awards ceremony, held at a Stockholm Volkswagen dealership, which Mr. Richardson and his family attended. Award notwithstanding, a highlight of the event for him was experiencing the latest-generation Scirocco, a sports coupe that Volkswagen does not export to the United States, but whose first generation Mr. Richardson once owned.

While traffic designers have yet to approach Mr. Richardson about a Speed Camera Lottery pilot program, it would seem he is receptive to any traffic-calming measures that produced safer streets. “Coincidentally, on my first day back from Stockholm after accepting the prize, I was hit on my bike by a car that ran a stop sign,” he said. “Now that’s irony.”