FORT WORTH, Texas – For years, bikeshare programs have been associated with big, heavy and slow bikes.

But now in Madison, Wisconsin, riders are pedaling on electric-bikes, or e-bikes, an increasingly popular type of bicycle equipped with a motor. When a rider puts pressure on the pedals, the motor engages to give riders a boost.

In late June, Madsion became the first city to replace its entire bikeshare fleet with electric bikes. And it's part of a growing trend.

In recent years, more bikeshare programs have adopted the technology in hopes of attracting new riders and improving the experience for existing riders. "In the past two years, we've seen a huge surge in the popularity and inclusion of e-bikes," says Samantha Herr, executive director of the North American Bikeshare Association.

As of early August, 41 out of the 192 cities in the U.S. that have at least one bikeshare system had incorporated e-bikes, also known as pedal-assist bikes, Herr says. And many of these systems are already seeing significant benefits, including a jump in ridership.

As a whole, bikeshare usage has grown every year from 2010 to 2017; the number of trips taken increased by 25% from 2016 to 2017 alone. In 2015, a study published in the journal Transport Reviews showed that Washington, D.C., and Minneapolis replaced car rides with bike rides 8% and 20% of the time, respectively. Other research has also made links between bikeshare and the reduction of traffic congestion in some cities, Vox reported in 2017.

Now existing bikeshare programs, which are typically in the form of private-public partnerships, see e-bikes as the future to seeing bigger gains.

In Madison, which now has an entirely electric fleet, "we've seen 1.5 to 4 times the ridership, depending on the day, compared to before," says Lisa Snyder, executive director of Madison BCycle.

Fort Worth, which added 50 e-bikes to its 350-bike system in April, is also seeing similar results.

Since being introduced, e-bikes rentals have actually outpaced regular bike rentals in the city.

"In the couple months since we've had them, our average check-out on an e-bike is 1.7, and the average of regular bikes is less than 1," says Malorie Sarsgard, assistant director of Fort Worth BCycle. She also expects to see a steady increase in ridership over the long-term thanks to the availability of electric bikes.

One of the ways electric bikes are improving ridership is by opening the door to people who may have never considered biking for transportation, including older people and those who are less physically active.

"Out in the community, the feedback we get is that bikes are heavy, or 'I don't cycle that often.' People feel like they need to have experience with cycling," Sarsgard says. "Electric-assist bikes meet you where you are. We're hoping to introduce a whole new type of rider to bikeshare."

That's because, for the rider, e-bikes require far less effort. As riders engage the motor through pedaling, they're able to climb hills or go for long rides, even when the rider isn't in the best physical shape.

Advocates of the e-bike movement say there's clear evidence of the benefits. In 2015, researchers found that, in Norway, e-bikes get people to ride more: Participants took more rides (from 0.9 to 1.4 per day) and rode longer distances (nearly double) than the control group. A 2016 clinical trial showed there are health benefits to riding pedal-assisted bikes, even though they make biking easier for the rider.

A more recent study from April found that access to e-bikes could increase bike commuting; compared with those who had a regular bike only, e-bike riders in the study cycled more often to work and for longer distances. Because some riders also feel pressure to keep up with the pace of traffic, e-bikes provide that extra speed and confidence they need to ride on the street, Sarsgard says.

Despite their success in some cities, Motivate, a bikeshare provider owned by Lyft, pulled e-bikes in Washington, D.C., New York City and San Francisco earlier this year after riders reported safety issues associated with faulty brakes.

Lyft e-bikes are now up-and-running again in San Francisco and they will re-launch in New York this fall, a spokesperson for Lyft confirmed by email. In Chicago, Lyft will also be adding more than 10,000 brand-new e-bikes by 2021.

Jump, the Uber-owned provider of dockless bikes and scooters, also has e-bikes in nearly 20 cities.

Herr says not every system needs e-bikes, but for Madison BCycle, there were few downsides to the full switch to electric. Because e-bikes have an on/off button, people who don't want the motor don't have to use it, and despite the fact that electric bikes cost more to maintain, Snyder expects an overall increase in ridership.

"The climate in Madison is completely ready for new technology and innovation and modern bike share," Snyder says. In addition to Madison already being a strong bike town – they've scored high in multiple bike-friendly rankings – the city's new mayor is an advocate for improving biking as a form of transportation in the city.