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This week, Portland contracted with Alta Bicycle Shares to launch a bike sharing system in the city.
The idea is to create an affordable and convenient form of public transportation, and one of its goals is to reduce car trips and help the city cut greenhouse gas emissions by allowing more people to bike and take public transit instead of driving.
What is bike sharing’s track record for achieving environmental goals? As you can see in the map above, there are quite a few bike share programs operating worldwide. Many have tried to show that bike sharing actually reduces car trips and the associated pollution.
According to Denver’s B-Cycle bike sharing program, a 4-mile bicycle trip keeps 15 pounds of pollutants out of the air that would have been emitted by a car driving the same distance.
But to prove the environmental benefits of bike sharing, you need to show that people are actually riding shared bikes on trips that they would have taken by car.
A survey of Washington, D.C.’s Capital Bikeshare members showed the program replaced a total of 5 million driving miles in 2011.
Members on average reported driving 523 fewer miles per year, avoiding the equivalent of 487.7 pounds of carbon dioxide.
A survey of riders in Denver revealed 43 percent of B-Cycle rides replaced car trips, which avoids burning 15,868 gallons of gasoline and emitting 312,121 pounds of carbon.
A survey of Minneapolis’ Nice Ride members found 20 percent of the trips taken by bike would otherwise have been taken by car.
And a report on bike share opportunities in New York City noted that bike sharing in Lyon, France, shifted 1,000 car trips to bicycles every day and that 7 percent of the trips people take on Lyon’s shared bikes would have otherwise been made by car.
Earlier this month, Capital Bikeshare released a plan to grade the effectiveness of its program. It will look at will the ratio of bikeshare miles traveled to vehicle miles traveled over time to gauge whether bike sharing has actually reduced the overall miles traveled in cars.
They haven’t crunched the numbers yet, but it will be a good stat to check in on as Portland’s bike share program gets off the ground.