Expense was not Vienna’s only consideration, Ms. Reich said. “We always wanted to go greener,” she said. “We wanted to implement something new and help the technology improve.”

Their efforts have been influenced by a series of European Commission initiatives to address climate change and reduce dependence on imported fuel. The commission has set a goal for member states to reduce transportation emissions by 60 percent by 2050. Buses account for as much as 60 percent of the public transit in Europe, and 95 percent of those use gasoline or diesel fuel.

The initiatives have helped fuel a flurry of innovation.

Power Vehicle Innovation, a French manufacturer, developed an in-route charging technology called Watt that will begin testing an airport-grounds shuttle bus in Nice, said Epvre Delquié, marketing director for P.V.I. Watt’s charging poles reach out from a bus to pick up a potent jolt of electricity from chargers, called totems, installed atop bus shelters along the route. These 10-second blasts of power extend the buses’ range.

P.V.I. plans to sell and install each totem for about $78,000, which Mr. Delquié said was low compared with the cost of installing overhead electricity lines on an entire bus route. In France, savings on fuel could cover the outlay on infrastructure and the extra cost for electric buses within 10 to 12 years of operation, Mr. Delquié said.

Developments are not restricted to bus lines. European authorities are also working with makers of trams and trains to find smarter ways to connect forms of electric transport.

Heilbronn, Germany, set a goal in 1993 of reducing vehicle traffic 50 percent by 2005, but transit infrastructure was weak. So the city decided to build an inner-city light rail and link it to regional service. The “Tram-Train” vehicles from Bombardier can run on the kind of current that powers city light rail or, by using an electronic converter, on a type of current that powers the heavy rail lines between Heilbronn and other cities. In this way, one vehicle can serve both systems.

The primary benefit is passenger convenience, said Andreas Berk, the light-rail technical project manager for the city. Commuters get more frequent service and no longer have to switch vehicles during trips. A closer connection to Heilbronn’s city center has also made the area more attractive to regional businesses and residents, leading to more private investment along transit lines within the city, Mr. Berk said.

These technologies are not yet a clear economic success. For now, city governments, like Heilbronn and Vienna, regularly subsidize ticket prices. Some cities, cautious about vehicle and battery performance, are limiting electric buses to lines with lighter passenger loads and shorter routes. But companies say they are playing the long game, evolving their electric transit technologies to reduce air and noise pollution and add convenience that attracts additional passengers.