Pedal power is gaining popularity in Europ in the form of more and more cities creating their own bike sharing programs.

For mayors looking to ease congestion and prove their environmental bona fides, bike-sharing has provided a simple solution: For the price of a bus, they get a fleet of bicycles, and they can avoid years of construction and the approvals required for a subway. For riders, joining means cut-rate transportation – as well as a chance to contribute to the planet’s well-being.

The new systems are successful in part because they blanket cities with huge numbers of available bikes, but the real linchpin is technology. Aided by electronic smart cards and computerized bike stands, riders can pick up and drop off bicycles in seconds at hundreds of locations, their payments deducted from bank accounts.

“As some cities have done it, others are realizing they can do it, too,” said Paul DeMaio, founder of MetroBike, a U.S.-based bike-sharing consultant that tracks programs worldwide. “There is an incredible trajectory.”

The huge new European bicycle-sharing networks function less as recreation and more as low-cost, alternative public transportation. Most programs (though not Paris’s and Lyon’s) exclude tourists and day-trippers.