On May 27, 2013, New York City launched Citi Bike, a bike-sharing program with 6,000 bikes available at hundreds of stations located in Manhattan and Brooklyn. In making its case for the program, the New York City Department of City Planning argued that bike sharing would yield significant health benefits, notably by encouraging exercise. In addition to promoting physical fitness, several health professionals have contended that increasing the presence of bikers on the roads may improve cyclists’ safety. David Vlahov, the dean of nursing at the University of California, San Francisco, recently told the New York Times, “The more people bike in a community, the less likely they are to collide with motorists,” attributing this effect to an increased awareness among motorists of bike riders.
Although many proponents of bike-sharing have emphasized these potential health and safety benefits, programs such as Citi Bike also raise important safety concerns. Biking injuries are very common; the Centers for Disease Control has estimated that every year 550,000 people will be treated in emergency departments for cycling-related injuries.
There have already been several crashes among Citi Bike users (although one injured Citi Bike rider was apparently more concerned about incurring late fees than about his condition as he was being loaded onto an ambulance).
One of the principal factors in bike safety is helmet use, which is encouraged but not required in New York City. There is strong evidence that bicycle helmets effectively prevent injuries. One review of the literature estimated that helmets reduced head and brain injuries 63-88% among cyclists of all ages. And a 2012 study found that not wearing a helmet was associated with more than three times the odds of sustaining a fatal injury while biking. In a segment focused on the new Citi Bike program, even the Daily Show highlighted concerns over the risks of biking without a helmet. After observing that many novice riders would try out biking on the streets of New York without head protection, Jon Stewart whispered with a terrified look, “A lot of people are going to die.” He quipped that this would present a lucrative business opportunity: a street brain removal service in which “gray matter is no matter.”
But are bike share cyclists less likely to wear helmets than people using their personal bikes? A team of researchers, led by Dr. Christopher Fischer of the Department of Emergency Medicine at Harvard Medical School, recently addressed this question by conducting a prospective observational study of adult cyclists in two American cities, Boston, MA and Washington, DC. The researchers studied 3,037 cyclists, including 562 bike share users, at various time points and days of the week. They found that 81% of bike share riders rode without helmets, as compared to only 49% of riders using their personal bikes.
The authors calculated odds ratios, which compared various exposures—type of bike use, rider gender, day of the week—with respect to riding either with or without a helmet. After adjusting their model for time of week, rider gender, and city, the authors found that bike share users were over four times more likely to ride without a helmet compared to other cyclists. They also found that men and weekend riders were significantly more likely to ride without helmets, as shown in the figure above.
The findings comparing helmet use among bike share users with personal bike cyclists seem intuitive. Presumably, people who have invested in a personal bike are also more likely to purchase and use their own safety equipment. By contrast, helmets are not available for rent at Citi Bike stations. Furthermore, logistical and hygienic concerns present significant barriers to incorporating helmets into a bike share program. People may not be inclined to carry a helmet with them or to share headgear with strangers.
Given these challenges, how can injury prevention professionals foster increased helmet use among bike share users? There is no singular answer. New York City’s Department of Transportation has been providing some free helmets and assistance with helmet fitting, although one New York Times reporter found that demand greatly exceeded supply. Public information and outreach campaigns may help increase helmet use among children, and mandatory helmet legislation has been associated with fewer head injuries among children. Yet it is not clear whether these interventions are effective among adults. Furthermore, New York City officials have resisted imposing a mandate, asserting that requiring helmets would reduce ridership.
Bike share programs offer the possibility of convenient transportation, as well as healthy and fun physical activity. As Anne Kadet humorously observed in a story on her Citibike experience, “When you travel by bike, you’re no longer a rat trapped in a train car. You’re a rat blazing wild and free through the city.”
But wearing a helmet while blazing through the Big Apple on two wheels helps ensure our fires are not extinguished. Our gray matter does matter.
Update, July 26, 2013: Beginning on July 25, 2013, bike rental company Bike and Roll NYC began renting sanitized helmets to Citi Bike users for $3 a day or $15 a week.
Edited by Dana March and Joshua Brooks