A、Shorter car trips produce more pollution for each kilometer driven. B、Longer car trips produce more pollution for each kilomet

More Americans than ever are riding their bicycles to work instead of driving. They are doing this because of gas prices, a slowing economy and concerns about the environment. Andy Clark is the executive director of the League of American Bicyclists. His group supports bicycling for fun, fitness and transportation. Clark says this is good news for the environment. He says riding a bicycle to work does not burn fossil fuel or create dangerous pollutants. Experts say the effects are the most important on short trips.(20)Shorter car trips release more pollution into the air for each kilometer driven. This is because the device in a car engine that reduces the harmfulness of emissions needs to warm up before it can work well. Last year, the Pacific Northwest city of Portland, Oregon, had the highest percentage of bicycle commuters in the United States. Portland has been doing progressive city planning for many years to create special paths for bike riders. Andrew Land is one of Portland’s citizens who bikes to work every day. Mr. Land is thirty-three years old and has never owned a car. He has biked to work for twelve years.(21)Before moving to Portland six years ago, he lived in Washington, D.C. But he was hit by a car twice while biking to work there. That has not happened in Portland where there are special roads for bicycles. Mr. Land bought a house near these special bike lanes. He rides almost five kilometers to work each day. He also uses the sixty-four kilometer bike path around the city.