With gas just shy of $4 a gallon, the alternative-transportation wheels are spinning for people in mid-Michigan.

"They've been coming in, buying new bikes, bringing in their old bikes and getting them repaired," says Dirk Bus, manager of Eric's Fitness and Cycling in Lansing.

Bus says new bicycle sales are up 20 percent from the same time last year, and bike accessory sales are through the roof.

"What I've really noticed is the extra numbers of racks and baskets people are buying-- [sales] have probably quadrupled," Bus says. "[They use them] to get groceries at the corner store, get a gallon of milk..."

People like Jessica Yorko, who works for the Mid-Michigan Environmental Action Council.

She uses her bike to "take my kid to school, I'm driving to work, I'm using it to go to the store to pick up a few things."

The environmentalist says biking saves her hundreds of dollars a month in gas. Now, she says, her peers are trading their cars for bikes- and enjoying the health benefits, too.

"For me, it's the difference between eating cheesecake," she jokes.

But if the demand for this two-wheeled transportation keeps up, people could find themselves standing in a waiting line before they're riding their very own bikes.

"The manufacturers haven't anticipated this," Bus says of the demand. He says already certain bikes are becoming scarce, and picky shoppers might have to wait four to six weeks for their bikes.

But with gas prices showing no sign of slowing down, the bike-riding trend might still be full speed ahead.