Science First Look

Yellow taxis are safer than blue ones, says science

The relative visibility of yellow cabs make them 9 percent less likely to be rear-ended than blue ones, a large-scale study of taxis in Singapore has found.

A red and yellow taxi rests against a pole after a traffic collision with a white Uber vehicle (at rear) in downtown Toronto, Ontario on Saturday.
Chris Helgren/Reuters
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Are your city’s streets flooded with bright yellow taxis, or do the cabs blend in with other vehicles in traffic?

That detail might seem small, but new research shows that a taxicab’s color has an impact on how likely other vehicles are to crash into it.

A new study from the National University of Singapore found that yellow taxis are involved in rear-end collisions 9 percent less frequently than blue cabs. Published Monday in Proceedings of the National Academy of Sciences, the study’s findings suggest that the vibrant yellow color makes the vehicles more visible to other drives, catching their eyes and helping them to avoid collisions more frequently. 

“Although there is anecdotal evidence on higher accident rates for dark coloured vehicles, few studies have empirically established a strong causal link between colour and accident risk,” Teck-Hua Ho, a professor at the National University of Singapore and the study’s leader author, said in a statement. ”The findings of our study suggest that colour visibility should play a major role in determining the colours used for public transport vehicles.”

Yellow cabs have become iconic symbols in cities such as New York, but many companies in other cities have opted for more subtle colors. A University of Chicago study some 100 years ago concluded that yellow was the easiest color to spot, prompting a cab company to select it so passengers could easily hail the cars as they passed through crowded streets.

Today, that choice seems to play a role in helping other drivers avoid the vehicles as well.

For 36 months, researchers tracked 4,175 yellow taxis and 12,525 blue taxis from the same Singapore company. Additionally, they examined three months of data from some 3,000 GPS logs, controlling for differences in distance, number of stops, and the speed driven.

After also ruling out differences in age and level of education of drivers, researchers were able to conclude that the color played a role in avoiding collisions, confirming decades of observational and anecdotal hunches.

The researchers found that the effect was strongest in darkness under street lighting, because of the way yellow stands out against dark backgrounds. 

Overall, a regular taxi passenger is like to experience one crash over 40 years in a yellow taxi, compared to 1.1 in a blue cab. While that slight bump may seem insignificant to a passenger, it has larger implications for cab companies and drivers, who spend time and money repairing cabs in their large fleets that are involved in crashes.

Researchers say the findings could have implications for colors of vehicles involved in public and private-hire transportation, and hope to conduct similar studies to uncover any benefits to choosing certain colors in those modes of transportation.

“We are keen to further validate the findings of our study by looking at the use of yellow in other types of public transport, such as school buses,” Professor Ho said. “For instance, we hope to compare the accident rates of yellow school buses against other colours to find out if yellow is indeed a safer colour for school buses. Furthermore, we are also interested to look at private-hire vehicles and do a comparison of the accident rates of vehicles that are of different colours.”