Abstract
Our research goal is to provide “fun” for drivers as a reward for safe driving, and to encourage spontaneous safe driving. An expressway driving game, which encourages drivers to keep the speed limit spontaneously, was proposed in our previous study. The present manuscript discusses the effectiveness of the game on driver behavior by using dozens of normal drivers’ data. The results revealed that many drivers felt fun for the game, and the game could provoke spontaneous behavioral change of keeping the speed limit.