This study examined the effectiveness of various financial incentive schemes for improving drivers’ safety performance, specifically in regard to speeding, tailgating, and frequent lane changing without signaling. The study examined the hypothesis that, with regard to modifying unsafe driving behavior in a sample of professional bus drivers in Israel, small yet reliable rewards are more effective than rewards that are large but rarely obtained. While this hypothesis has been tested and partially supported in laboratory studies, the current study is the first to test it in real-world conditions. This study demonstrates that a combination of surveillance, rewards (monetary compensation), and informing the drivers about their driving performance in real time produces a lasting and significant decline in traffic violations. The results show that financial incentives are effective for encouraging safe driving behavior. Simultaneously, the results show some indications that small yet probable rewards may be more effective than large but uncertain ones. This study also demonstrates that the improvement in behavior continued during the period immediately after the experiment.