Safer to ride in yellow taxis

"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. The findings of our study suggest that colour visibility should play a major role in determining the colours used for public transport vehicles. A commercial decision to change all taxis to yellow may save lives and potentially reduce economic losses by millions of dollars. Our results are also noteworthy to smaller taxi companies and to drivers who use their private vehicles as taxis to work for private-hire car services," said Professor Ho Teck Hua, NUS Deputy President (Research and Technology) and Tan Chin Tuan Centennial Professor.

The study was led by Prof Ho, and conducted in collaboration with Associate Professor Chong Juin Kuan from the NUS Business School and Assistant Professor Xia Xiaoyu from The Chinese University of Hong Kong Business School. The findings of the study were published in scientific journal Proceedings of the National Academy of Sciences (PNAS).

Yellow taxis have fewer accidents than blue taxis

To test whether there was a causal relationship between the colour of a taxi and the number of accidents the taxi had, the research team analysed data from the largest taxi company in Singapore, which involved millions of observations on the company's drivers and taxis, and accidents involving these taxis. Upon reviewing the data from 4,175 yellow taxis and 12,525 blue taxis, the researchers found that yellow taxis have about 6.1 fewer accidents per 1,000 taxis per month.

Translating the findings to evaluate the physical risk to a taxi passenger, the research team noted that over the course of 40 years, a passenger will experience 1.1 accidents in a blue taxi, compared to 1 accident in a yellow taxi, which is a 9 per cent reduction in accident rate.

Substantial cost savings for taxi operator

The researchers also studied the economic impact of changing the colour of the entire fleet of taxis to yellow. The Singapore taxi company involved in the study owns about 16,700 taxis in a ratio of one yellow to three blue taxis. If a commercial decision is made to switch from blue to yellow taxis, 76.6 fewer accidents would occur per month or 917 fewer accidents per year. Assuming an average repair cost of S$1,000 per car and a downtime of six days, switching the colour of all taxis to yellow could generate an annual savings of S$2 million.

Next Steps

"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. 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," explained Prof Ho.