John Metcalfe is CityLab’s Bay Area bureau chief, based in Oakland. His coverage focuses on climate change and the science of cities.
Researchers in Singapore have crunched the numbers of crash rates by vehicle color.
Few people probably stop themselves before getting in a taxi to ask, Wait—what color is this car? But it’s not as strange a question as it might seem, as there’s evidence that a cab’s hue influences its chances of getting into a wreck.
That’s according to Teck-Hua Ho and other researchers who analyzed three years of accident rates in Singapore. They found that by getting into a yellow taxi instead of a blue one, you lower your accident risk by 9 percent. Yellow vehicles had roughly 6 fewer crashes per thousand taxis than their blue brethren per month, which the researchers ascribe to improved visibility. (Despite appearances, this study was not sponsored by the Yellow Cab Association of Singapore.)
It might seem like an obscure topic to put under a microscope, but optimal cab color has been a matter of consideration for more than a century. The researchers provide some nice background in their new study, which is published in the Proceedings of the National Academy of Sciences:
Yellow has been a popular color for taxis since 1907, when the Chicago Yellow Cab Company chose the color based on a survey conducted at the University of Chicago. The survey showed that yellow was the most noticeable color, which would make it easy for potential passengers to spot a yellow taxi in the sea of mass-produced black cars prevalent at the time (until 1914, “Japan Black” was the only paint color that would dry fast enough to be used in Ford’s mass-production process). More than a century later, it turns out that yellow was a wise choice, not only for potential passengers but also for actual passengers because yellow taxis seem to have fewer accidents than blue taxis.
Over the years there have been several scientific inquiries into vehicle color and accident risk. A 2003 study in New Zealand found that brown vehicles were more likely to send a body to the hospital than white ones, for instance, backing up a paper the year prior from Spain that asserted dark-colored cars in general were more dangerous. The team that was led by Ho, a professor at the National University of Singapore, performed their own experiment using accident data from the city-state’s biggest taxi company, which operates both a blue and yellow fleet with a common pool of drivers.
“We chose these two colors because they are the two colors used by the largest taxi company in Singapore—the company’s taxis account for approximately 60 percent of all the taxis in Singapore,” emails Ho. “The two colors are a remnant of a merger between two firms, one of which used yellow, and the other blue.”
After ruling out demographic differences like age and experience among drivers of both taxis, the researchers found a clearly enhanced risk among blue cars, especially when driven at night under street lighting. (This environment enhances the contrast of yellow against a dark background but diminishes that of blue.) They conclude that yellow cars give other drivers an unconscious heads-up of their presence, allowing them to swerve or brake to avoid accidents, especially rear-enders.
So should all cabs be yellow? Ho and his crew think so. If Singapore’s largest cab operation changed to an entirely banana-hued fleet, they say it would probably prevent 917 accidents a year. With an extrapolated repair price of $700 and an out-of-commission time of six days per vehicle, a simple switch could save the business $1.4 million a year. (Not counting the cost of all those paint jobs.)