Bicycle riders are more likely to be seriously injured in vehicle crashes at intersections where streets don't meet at right angles, according to a study in New York City.
Planners could factor in this added risk when designing bike lanes and other protections for cyclists, the study authors write in Injury Prevention.
Bicycling offers great health benefits but issues of safety are a huge barrier to people choosing bikes as their transportation, lead author Morteza Asgarzadeh of Harvard T.H. Chan School of Public Health in Boston told Reuters Health.
In the U.S., most bicycle-vehicle crashes occur at intersections, "yet we still don't have proper protective bicycling infrastructure at intersections across the country," Asgarzadeh said by email.
It would be very expensive for cities to overhaul all intersections, so the research team sought to identify which intersections might pose the greatest risk, Asgarzadeh said.
The researchers mapped the location of 3,266 bicycle and car crashes using GPS information recorded by New York police in 2011. They used police records and Geographic Information Service (GIS) maps to determine intersection angles, street width, presence of bike lanes, speed limits and average traffic level at the crash locations.
The study team also collected details about the accidents including the age and sex of the bicyclist, time of day, road conditions, type of vehicle involved in the crash and severity of the bikers' injury.
The majority - 60 percent - of bike and car crashes happened at street intersections.
Compared with crashes at right-angle intersections, crashes at non-right angle intersections were 37 percent more likely to results in severe injury for cyclists.
Crashes that didn't happen at intersections were also 31 percent more likely to cause serious injury compared with crashes at right-angle intersections.
When crashes were not at an intersection, they were more likely to happen on narrow streets less than 100 feet wide, although street width wasn't linked to the severity of cyclist injuries.
When planning intersections, one key for safety is making sure drivers can see bicyclists from a distance, said Yinhai Wang, a transportation researcher at the University of Washington in Seattle who wasn't involved in the study.
When intersections are not at right angles, the distance drivers can see goes way down, Wang told Reuters Health.
Bikers should also take charge of their safety as well, Wang said. "Education in schools on the proper operations of bicycles and intersection safety awareness is every effective too," he said by email.
Asgarzadeh noted that while cities may need to spend a large amount to improve intersections, money might be saved by not needing police officers to monitor dangerous areas.
Wang offered safety advice for bikers: Always follow the traffic rules and signals, always be cautious when on the road and never assume automobile drivers can see you and know what you're going to do next, and pay more attention to safety when riding near a truck or a bus.
"We hope a more conscientious urban design along with higher awareness among bicyclists and drivers can improve perception of safety to help more people choose bicycles as a mode of transportation to get to work or around cities," Asgarzadeh said.