TOKYO — Whenever Shigeki Kobayashi spots a salaryman on a bicycle with his bag in the front basket, he knows that he is watching a novice bike commuter: putting the heavy load up front makes steering harder, an elementary mistake.

Mr. Kobayashi also realizes that someone is new to street cycling when the rider is on the sidewalk. “Some people mistakenly think it is safer on the sidewalk,” he said. “That’s wrong, because on the sidewalk there is greater chance you’d bump into someone or something.”

Mr.Kobayashi is director of the Bicycle Usage Promotion Study Group, a nonprofit organization that promotes usage of bicycles in Tokyo. Since March 11, when an earthquake devastated northern Japan and rattled the Tokyo metropolitan area, the streets of Suginami ward, where he lives, have teemed with wobbly bikers pedaling their way to work.

“The increase was sudden and visible,” he said during an interview.

Over the past 20 years, more commuters in urban areas like Tokyo have been switching gears and choosing to bicycle to work instead of using trains and cars, citing concerns for health, environment, costs and an escape from packed trains. The catastrophe last month has now converted some of the holdouts by proving one more benefit to cycling: you have a means to go home when the trains stop moving.