For the Sorensen family of Alameda, the sound of knuckles rapping on the garage door was a familiar annoyance. It was their 13-year-old son, Brandon, who knocked on the door so frequently to put away his bicycle that his parents finally got him an access code to open the garage on his own.
“Now, I would love to get up every couple of minutes to get him,” said his father, Kurt Sorensen, a Southwest Airlines employee.
Brandon was riding his bicycle through an Alameda intersection on a rainy Monday afternoon last month when he was struck by an S.U.V. By chance, his mother, Tammy, came upon him lying in the street as she drove past. She held her son one last time; he died at a nearby hospital.
A Bay Citizen analysis of bicycle accident data from the California Highway Patrol found that young cyclists like Brandon are at the highest risk. The analysis shows that in the Bay Area cyclists ages 10 to 19 were involved in more traffic collisions — more than 3,200 from 2005 to 2009 — than any other age group.
Nearly half of those accidents involved boys ages 12 to 16.
In a region filled with thousands of adult cyclists, including daredevils who barrel through congested cities at high speeds, data showing that youngsters are most prone to accidents surprised even bicycle advocates. They said it showed the need for early education about traffic laws and safety.
The highway patrol compiles information about bicycle accidents from local police reports. According to the data, San Jose had 434 collisions involving teenagers, the most of any Bay Area city. Oakland was second with 193. (The Bay Citizen’s Bike Accident Tracker is at baycitizen.org/data/bike-accidents/.)
“I would have thought it would be males in their 20s” who would have the highest accident rates, said Renee Rivera, head of the East Bay Bike Coalition. “Anecdotally, I see mostly young adults cycling.”
In fact, cyclists in their 20s had the second-most collisions with motorists — about 3,100 from 2005 to 2009.
The data showed that teenagers were judged by the police to be at fault 63 percent of the time. By contrast, cyclists in their 20s were faulted in 46 percent of accidents.
The police are still investigating Brandon Sorensen’s accident, and the cause is unknown. The driver is cooperating, and no charges have been filed, according to the Alameda Police Department.
The police and experts in bicycle safety said adolescents, as inexperienced riders, often put themselves in danger because they are unfamiliar with traffic laws. The California Vehicle Code requires cyclists to ride on the right side of the road and follow all traffic rules, including stop signs, traffic lights and signaling.
“Bicyclists don’t think they’re vehicles on the roadway,” Sgt. Steve Paich of the Oakland Police said. “They feel like they should be treated like pedestrians.”
Sergeant Paich said many teenagers think it is legal to ride their bicycles in the crosswalk, for example. “Riding in the crosswalk,” he said, “means you’re riding on the wrong side of the road,” which is the ticketing category for riding in a crosswalk.
Adolescent cyclists were cited for being on the wrong side of the road two and a half times more than for any other individual violation, the data showed. Adolescents were found to be on the wrong side of the road more than any other riders.
A sampling of police reports shows how youngsters’ ignoring traffic laws can put them in harm’s way.
In one accident, a woman was driving along Eighth Avenue in Oakland when a 15-year-old cyclist ran a stop sign and entered the intersection. Trying to avoid him, the driver lurched onto the sidewalk, but the cyclist was thrown onto the hood of the car before rolling off into the street.
The teenager was lucky. He escaped with a few stitches on his head and some scrapes on his leg. His name and the driver’s were redacted from the police report.
In another instance, a 12-year-old boy ran a red light at the intersection of Hegenberger Road and Edgewater Drive in Oakland and was struck by a car. The driver was accelerating after the light turned green, according to the police report. The boy was not injured, but was cited for not having brakes or wearing a helmet.
Stacey Perry, the head of bicycle safety for the Traffic Safety Unit of the Oakland Police Department, said persuading children to wear helmets is one of her biggest challenges. California requires cyclists under 18 to wear helmets.
“I still have to say it becomes difficult to get teenagers to wear a helmet,” Ms. Perry said. “You want to put every kind of spin possible. To be honest, they really don’t want to hear about the safety part.”
The highway patrol rarely includes whether the rider was wearing a helmet when an accident occurs because the police reports do not provide a checkbox for that information. Only 88 of more than 14,000 records contained information about whether a rider was wearing a helmet.
David Maletsky, a 40-year-old Alameda cyclist who writes for the Cyclelicious blog, said he believes he has never been in an accident because his father often recited the traffic rules to him from the driver’s seat of his truck. Mr. Maletsky now does the same while driving with his 9-year-old son.
“Young people are learning all the time,” Mr. Maletsky said, “whether you are teaching or not.”
A few weeks after Brandon Sorensen’s accident, Bonnie Wehmann, the East Bay Bicycle Coalition’s education director, led a three-and-a-half-hour workshop in an Alameda church basement, offering instruction on equipment, safety and the law.
Ms. Wehmann’s workshop drew mostly adults, but a few teenagers went with their parents.
“To be honest, we really wanted to do the workshop after the accident happened,” said Judy Kleppe, who came with her son Will Schmidt. “The more knowledge about it we have as parents, the less fear we’ll have letting them go out there.”
Will, 15, said he learned where to ride to make himself more visible to motorists and how to avoid open car doors. He said he was still confident he could protect himself despite accidents like the one that killed Brandon.
“I know how rare it is,” he said of such collisions. “It doesn’t make me want to stay off the roads.”
Hundreds of community members turned out last week for Brandon’s memorial service. They filled every chair and lined the Lincoln Middle School gymnasium walls three deep. For many students, Brandon was the first person they had ever known to die.
Isaiah Zulu, 12, said he and Brandon were “shooting hoops” the day of the accident. Brandon left on his bike but never made it home. Isaiah was home sick the next day when he heard the news from his mother.
“I just broke into tears,” Isaiah said. “We sat next to each other on the first day of school.”
Mourners heard from Brandon Stanford, a family friend, who said Brandon Sorensen had saved up for a new bicycle by doing odd jobs around the neighborhood. He kept his money in a plastic bag and had recently sold two old bicycles on Craigslist.
When the Sorensens spotted the perfect Italian touring bike at a garage sale recently, they called their son and said the owner was asking for $50.
Offer him $40, he said, according to Brandon Stanford. Through their tears, the mourners laughed.
Brandon was riding that bike the day he died.
Sydney Lupkin 