The next time you’re about hop into a taxi, you may want to check its color first. A new study finds that yellow cabs are 9% less likely to be rear-ended than blue ones. For 36 months, scientists tracked 4175 yellow taxis and 12,525 blue taxis from the same Singapore-based fleet; they also used 3 months of data from more than 3000 drivers’ GPS logs to rule out differences in driving speed, number of stops, and distance covered as confounding factors. There were also no significant differences in the age, education level, or experience of drivers assigned to yellow versus blue cabs. The sheer volume of data—totaling millions of observations—makes this the first study able to identify vehicle color as a main contributor to accident rates, the team reports today in the Proceedings of the National Academy of Sciences. Visibility conditions—daylight versus nighttime street lighting—also played a role. Under street lighting, yellow taxis were 19% less likely to be rear-ended than blue, compared with 5% less likely to be rear-ended during the day. The scientists conclude that yellow is more noticeable, especially in low lighting, giving other drivers more reaction time to avoid accidents. Converting the whole fleet to yellow would save about $1.4 million a year, the researchers say. They also plan to compare the visibility of other car colors and investigate the implications of vehicle colors for ride-hailing services like Uber and Lyft.