Transit ridership is down in nearly every major U.S. city across the country. The prevailing narrative is that those riders are being tugged away by cars, most notably, cars operated by Uber and Lyft. Improving transit service might be enough to win riders back, but will cost cities money. What if there was a cheaper, more nimble solution cities could deploy? A new study suggests cities might boost ridership by doubling down on bike share.

Presented by University of Kentucky researchers at January’s Transportation Research Board Annual Meeting, the study “Understanding the Recent Transit Ridership Decline in Major U.S. Cities: Service Cuts or Emerging Modes?” started out by looking at the connection between service cuts and the loss of transit ridership. As University of Kentucky engineering professor Gregory Erhardt tells Curbed, the researchers believed there was more to the story than just reduced service.

“It didn’t seem intuitive to me that it could all be due to service cuts because most service cuts were introduced during the recession,” says Erhardt. The most dramatic ridership dips didn’t happen a decade ago, but in more recent years.

Using transit data and census data, Erhardt and his team focused on how ridership in seven major cities—Boston, Chicago, Denver, Los Angeles, New York City, San Francisco and Washington, D.C.—was impacted by a range of factors, including gas prices and car ownership.

While each city faced different challenges, all cities shared two critical turning points, says Erhardt: the introduction of bike share and the introduction of companies like Uber and Lyft (known as “transportation network companies,” or TNCs). The study looked at the period from 2002 to 2018, during which time all seven cities added bike-share systems and TNCs. And the effects were remarkably consistent.

When cities introduced ride-hailing services, transit saw a 1.3 percent per year decrease in heavy rail ridership and a 1.7 percent per year decrease in bus ridership. What’s more, the decrease “builds with each passing year,” according to the study, meaning cities would have to work harder to recoup ridership losses.

In San Francisco, for example, where Uber started taking passengers in 2010, the cumulative effect means that the city’s transit agencies would have to improve service by 25 percent just to overcome the impact of companies like Uber and Lyft.

However, Erhardt and his team also found that in cities where bike share launched—and this study looked at data from traditional docked bike share, not newer dockless bike or scooter share, although the study does mention those modes, too—there were positive impacts on some types of transit ridership.

After the introduction of bike share, subway ridership in cities increased by an average of 6.9 percent and light-rail ridership increased by 4.2 percent.

Bike share still led to an average 1.8 percent decrease in bus ridership, a trend that’s nearly universal across the board. According to the American Public Transportation Association data, 32 of 37 of the U.S.’s largest bus systems saw ridership declines in 2017.

But that may be because cities with thriving bike share programs often lose bus riders to bike share, as is likely happening in New York City. Although bus ridership might suffer, it’s still a net positive if a city is trying to reduce travel times, vehicle-miles traveled (VMT), or emissions, Erhardt notes.

“If you’re putting someone on a bike, that’s something transit agencies are going to have to pay attention to, from a revenue perspective,” he says. “But the biggest issue is where you take someone off the bus or off a bike, and put them into an Uber, adding to congestion.”

The recent Transit Center report “Who’s on Board” also looked at what factors were affecting transit ridership across the U.S. Based on surveys of riders in New York City, Chicago, Los Angeles, Pittsburgh, Seattle, Denver, and New Orleans, Transit Center framed its findings as a challenge for transit agencies to “win back” riders by improving service.

But there’s something else that’s important to note: Transit Center’s survey found that nearly a full quarter of respondents (24 percent) said they had just scaled back transit use in favor of car use. Only 9 percent had completely stopped riding transit.

If one out of four transit riders are simply opting for riding more occasionally—most are swapping an average of seven transit trips per month with car trips, according to Transit Center’s study—that means providing a different non-car alternative at the right moment might keep would-be riders from choosing cars. The key is presenting those options in the right place during the appropriate segment of the journey.

This week, Uber announced that more people in Sacramento are now riding its dockless electric Jump bikes than riding in Uber-managed cars. During the month of October 2018, 53 percent of trips booked through Uber were on Jump bikes, compared to 47 percent in cars.

What’s more, Jump bikes are being used an astounding six rides per bike per day, a remarkable number for any U.S. bike-share system. Uber now allows users to toggle between car, bike, and scooter options (where available), and recently began adding transit directions to its app.

The city doesn’t have correlating data to show how bike-share use is impacting transit boardings yet, says Jennifer Donlon Wyant, active transportation program specialist for the city of Sacramento (the city doesn’t get Uber’s data). But she is able to say that bike-share use has increased after the city made major bike infrastructure improvements.

“We’re proud [the city’s increased bike-share use] coincides with the implementation of 22 blocks of parking protected bikeways—and some buffered bike lanes, plus standard bike lanes—in our urban core this summer, plus 30 more blocks soon,” she tells Curbed. “As we implement our Vision Zero program and work to reduce greenhouse gas emissions, reducing VMT is key, and we’re working to support these goals.”

Especially in a country where over a third of all trips are three miles or less, Uber’s data paired with Ernhart’s study makes a compelling argument for expanding bike share, and particularly dockless bike share. Regardless of mode, it’s these types of trips—bus, bike, TNC—are the most interchangeable when it comes to urban transportation, says Ernhart. The average trip length for bus, bike share, and TNC ride in the cities studied were all right around the same—between two and three miles. (Scooter rides are more likely to be between one and two.)

Providing better bus service should absolutely be an important priority for cities to improve transit ridership. But cities shouldn’t ignore the power of providing ubiquitous bikes and safer infrastructure to help capture transit-savvy riders as they’re making decisions about their next move.