NEW YORK >> When she passes a row of shiny blue Citi Bikes in Manhattan, Yael Steren often wants to stop and take one for a ride. Then the doubt creeps in.

Braving city traffic without a helmet seems too risky. But carrying one around all day would be an inconvenience.

"I know how crazy the drivers are here," said Steren, 36, a personal stylist who lives in Greenwich Village.

Like many women in New York City, she has weighed the wind-in-your-hair joy of urban cycling with the pulse-quickening anxiety of steering between barreling trucks and decided against taking a spin.

When Citi Bike arrived here, it promised to spread the benefits of biking to the masses, an uphill push in a city where large potholes, heedless yellow cabs and darting pedestrians can make riding on busy streets seem like an activity best left for daring messengers.

But two years in, Citi Bike’s inroads have been decidedly uneven, with men far outnumbering women in using the bike-sharing system. A little time on Eighth Avenue on a recent morning, watching the stream of Citi Bike riders heading north past Pennsylvania Station and toward Times Square, was instructive. Man after man pedaled by, some in suits, others in jeans. From time to time, a woman on a Citi Bike rode by.

For the bike service, that is a problem. A new leadership team installed last fall has set out to recruit thousands of new users. Upgrades to troublesome software and plans for more stations have been welcome steps, but persuading more women to join is seen as vital to the success of Citi Bike. Today, women take about a quarter of all trips by Citi Bike riders and make up just under a third of its members.

"Women are early indicators of a successful bike system," said Sarah M. Kaufman, assistant director for technology programming at the Rudin Center for Transportation at New York University and an author of a new report on Citi Bike. "If you have more women riders, that means it’s convenient and safe."

Officials at Citi Bike say they are attracting a greater share of women than the citywide rate of female cyclists – about 21 percent, according to a study from Hunter College. The bike-sharing service is looking at more than just the safety concerns that seem to nag more at women than men, who insurance actuaries long ago concluded are more likely to engage in risky behavior, such as not wearing a bike helmet.

And there are other perceived obstacles, not unique to women but more commonly cited by them: They cannot ride with small children. They think the cost – $149 for an annual membership or $9.95 for a day pass – is too steep, especially on top of a subway pass. And they worry about arriving at work sweaty.

"I wouldn’t want to be gross the whole day," said Maeve McCarthy, 21, an intern at an interior design firm in Manhattan, who has not tried Citi Bike but said she would consider taking a nice ride through Central Park, if not commuting to work from Brooklyn.

The report by the Rudin Center said Citi Bike’s planned expansion this year to Long Island City in Queens and further into Brooklyn in Bedford-Stuyvesant and Greenpoint could help diversify its customer base, bringing in less wealthy riders and more women. The current 330 or so bike stations are in Manhattan below 61st Street and in a few Brooklyn neighborhoods near lower Manhattan, many of which are more affluent.

Women have avoided riding in bustling midtown Manhattan and often stick to less chaotic neighborhoods on the Lower East Side and in Brooklyn, the report said.

Citi Bike’s gender gap is part of a broader pattern among cyclists across the country; bike-share systems in Chicago and Washington also have more male riders. To woo women, Citi Bike is hosting rides with women’s cycling groups and trying to make cycling seem stylish.

The bikes appeared in the windows of Bloomingdale’s and in an episode of Comedy Central’s slacker millennial show "Broad City." The company recently posted a photo on Twitter of actor Leonardo DiCaprio and model Kelly Rohrbach kissing on Citi Bikes, and Vogue’s website praised model Karlie Kloss’ "practical chic" outfit while riding. Citi Bike has even dipped into cycling history, highlighting how bicycles symbolized independence for bloomer-wearing suffragists.

In June, the company introduced a newly designed bike that has a different seat and kickstand and feels lighter, which may appeal to women and less bulky riders.