A do-it-yourself approach to bike ridership data

Call it D.I.Y. traffic counting.

The process of pinning down exactly how many people ride bikes in Boston is a notoriously imperfect science. Ari Ofsevit, who runs the blog “Amateur Planner” — though he says he’s more “armchair” than “amateur” — was underwhelmed by the state’s data on bike use on Longfellow Bridge. The state’s most recent numbers, from 2011, suggest that a little more than 100 cyclists cross the bridge in a two-hour time frame during a peak period of the day.

Which, if you’ve ever been on the bridge during rush hour, seems like a shockingly low estimate.

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So Ofsevit hatched a plan to conduct his own ridership count, Ninja-style.

“Instead of getting mad, I got even,” Ofsevit wrote. “I did my own guerrilla traffic count. On Wednesday morning, when it was about 60 degrees and sunny, I went out with a computer, six hours of battery life and an Excel spreadsheet and started entering data.”

His results?

During the two-hour period he was stationed at the bridge, he saw 463 cyclists — more than four times state estimates.

He also discovered other interesting details, too — only about 6 percent of the cyclists crossing the bridge were on Hubway bikes.

Check out the full blog post here.