PHILADELPHIA (Reuters) — US cities that have long promoted bicycle use by commuters are now seeing a steady rise in the popularity of pedal power as gasoline prices soar.

Campaigns originally designed to cut down on traffic and pollution are now paying off for people looking for an option to driving with national gas prices averaging a record $4 per gallon ($1.06 per litre).

People in cities such as Chicago, Washington and Portland, Oregon, can take advantage of bicycle lanes, bike-friendly transit systems and bike-parking locations built in recent years.

"Twelve years ago, I would bike down to City Hall and often it was a lonely ride," said Ben Gomberg, Chicago's bicycle program coordinator. "Today, there are often 17 or 18 riders stopped at the intersections."

Unlike Europeans, Americans use bikes for transport sparingly, even though 40 percent of personal trips in the United States are two miles or less, according to bicycle advocates.

In a country famous for its love of cars and driving, less than one percent of personal trips are by bike compared with up to 30 percent in some parts of Europe, campaigners say.

But rates of bike use in some US cities are significantly higher thanks to recognition by urban planners of the environmental, economic and health benefits.

In Portland, widely regarded as America's most bike-friendly city, 5.4 percent of people said in a 2006 survey that the bicycle was their primary means of getting to work.

"In the last three years, we reached another acceleration point," said Scott Bricker, executive director of the Bicycle Transportation Alliance, an advocacy group. "Ridership is increasing exponentially."

The relative popularity of bicycling in Portland may be linked to bike lanes, locking facilities and programs that encourage public bicycling and safety education for children.

The city has 171 miles of bike lanes along its 2,568 miles of roadways and plans to increase that to 434 miles. Portland has 71 miles of bike trails and a third of its arterial roads have bike lanes or paved shoulders.

Portland's network includes 114 miles of "bicycle boulevards" — quiet streets where bikes have priority over cars and where traffic speed is restricted.

Those boulevards may be a better way of encouraging riding than traditional bike lanes where riders are still close to speeding cars, Bricker said.

In Chicago, pro-bike policies have resulted in 115 miles of bike lanes, more than 11,000 bike racks and 50 miles of dedicated bike paths along Lake Michigan, Gomberg said.

Around 1.5 percent of personal trips in Chicago are made by bike and the city aims to boost that to five percent by 2015.

In Washington, the proportion of people biking to work rose from 1.2 percent in 2000 to an estimated two percent in 2006, said Jim Sebastian, who heads the US capital's bicycle and pedestrian programme.

Bike lanes in Washington now stretch to 33 miles — 11 times longer than in 2001 — and more than half of the city's subway stops now have bike racks.

Later this summer, Washington plans to launch the first US bike-sharing programme in which users will pay $40 a year for a swipe card enabling them to pick up a bike from racks around the city and then return them to any other rack.