Given that electric vehicles coined the phrase "range anxiety," one might be inclined to think that taxis powered by a rechargeable battery would increase the stress levels of their drivers. But a recent study involving the electric version of London's famed "black cabs" found that the opposite is true.

The study was commissioned by the London EV Company, which manufactures electric taxis for London and other markets. The research was done in conjunction with the University of York and timed to coincide with Mental Health Awareness Week, which includes efforts to raise awareness of stress reduction.

Researchers sought to monitor the mental activity of taxi drivers, comparing those in electric taxis to drivers of diesel-powered models. Four professional taxi drivers were outfitted with electroencephalograms, or caps with electrodes to monitor brain activity. Drivers' heart rates were also recorded.

The drivers completed a series of test drives along a route around Regent's Park in central London. Those who took part in the study were already familiar with the controls of LEVC's electric TX taxi model.

Researchers recorded that the drivers of the electric taxi had higher levels of beta brain activity than diesel taxi drivers, indicating that they were concentrating more on driving tasks. This finding was especially noticeable when a driver was waiting at a traffic light.

"The study suggests that the quieter driving environment allowed cabbies to be in a more concentrated state of mind," said Duncan Williams, a University of York acoustics expert who designed and executed the test. "In other words, by removing the noisy diesel engine rumble, they are perhaps freed up to get on with driving in a more focused, but calm way. It's a fascinating result and, given the movement towards electric commercial vehicles, shows there are even more benefits of going electric than we might have previously thought."

The heart rate of electric taxi drivers was less variable than the heart rate of diesel taxi drivers, which researchers said was an indicator of greater mental calm. The study suggested that the quieter interior of the electric taxi may have been a factor in this finding, as noise levels were about five decibels lower than in the diesel taxi.

Drivers reported that they were happier overall when driving the electric taxi, and also reported lower stress levels and less distraction. Drivers were neither more nor less afraid or angry in the electric taxi than they were in the diesel taxi.

"Our aim with the TX was to make the world's most advanced taxi, a vehicle that would not only help reduce urban air pollution but improve comfort and convenience for passengers and drivers across the globe," said Chris Gubbey, CEO of LEVC. "We are delighted to find we have made a vehicle that is now proven to also make cabbies' working lives better.

Few studies have assessed the emotional levels of those driving an electric car. A 2015 study comparing 12 electric vehicle drivers to 12 people who had never driven this type of vehicle found that experienced electric drivers were less worried about range anxiety, or the fear that an electric vehicle will not have enough battery charge to reach a destination.