KYOTO — Kyoto has long been a mecca for school excursions, especially in May and June, but only recently have environmentally friendly taxis been gaining popularity as a means of touring the city.

As a way to contribute to the environmental cause, Yasaka Taxi Co. in Shimogyo Ward introduced one of Toyota Motor Co.’s low-emission Prius hybrid cars in May 1998 after carefully checking that the sophisticated computers of the vehicle would not affect the fare meters and other fixtures used in a cab. It was the first taxi company to introduce the hybrid car.

The Prius, which made its debut in December 1997, is powered by a combination gasoline engine and an electric motor. It discharges half the carbon dioxide of conventional cars of the same engine size and is twice as fuel-efficient as conventional vehicles.

Because the eco-car has been popular with passengers as well as with drivers, Yasaka has since increased the number of Priuses in its fleet to five.

“I like this car because it is comfortable to drive,” said cabby Toshiko Takeuchi, who has been driving the company’s first Prius for the two years since its introduction. “And this new image attracts passengers.”

The car is light blue, while most taxis in Kyoto are black. Passengers also like the cab’s quiet ride, the firm said.

Earlier this month, about 140 students from Ashikaga, Tochigi Prefecture, visited Kyoto, and those who were chosen to take a Prius tour let out shouts of excitement. The company’s five Prius cars are in full operation during this school-trip season.