Diane Bagues had just moved to San Leandro a few years ago from another state, and she was stunned one day when a motorcyclist sped down the middle of the freeway inches away from her car and one in the next lane.

“Lane-splitting scares the *&^%&* out of me,” she wrote in an email. “I’ve never seen this in any other state, and couldn’t believe it was legal here.”

She’s not alone. Kicking off the start of Motorcycle Safety Awareness Month, the state Office of Traffic Safety on Thursday released its first-ever survey on the controversial but legal practice of splitting lanes.

The survey found that 53 percent of drivers think splitting lanes is against the law but that 87 percent of motorcyclists do it. It also found that 7 percent of drivers admit to trying to block motorcyclists as they travel between lanes.

California is the only state to allow this common practice. While there is no law that deals directly with it, police say it’s OK when done safely at moderate speeds. That usually means when traffic is creeping along at under 45 mph, but not 65 mph, when roadway conditions are light.

Many motorcyclists and some traffic cops say splitting lanes makes them nervous, but they know it saves them significant time on the road.

“Without lane-splitting, I would never get to work,” said Eric Johnansen, who commutes across the Bay Bridge from Oakland to San Francisco. “It’s a life saver. But I know it freaks out the car people, and I also know that it’s not the safest thing I do all day.”

Officer D.J. Sarabia of the California Highway Patrol office in San Jose calls the practice dangerous, but he does it.

“As a motor officer myself for the last 11-plus years, I am very apprehensive to split traffic but must do so to do my job,” Sarabia said. “You definitely have to be aware of traffic patterns: speed of traffic, people making lane changes, stop-and-go traffic, etc.”

Motorcycle deaths have fallen since 2008 after a decade of annual increases and are down nearly 30 percent, while the number of people injured decreased by nearly 11 percent over the same period.

Yet the National Highway Traffic Safety Administration says that per vehicle mile traveled, motorcyclists are about 39 times more likely than occupants of a car to die in crashes. Yet most crashes are the fault of the motorist and not the motorcyclist.

Will Clark, of San Jose, was clipped by a car when he was lane-splitting at 30 mph alongside a South Bay carpool lane. “He hit me just as his turn signal flashed for the first time,” Clark said.

Safety officials say using turn signals is a huge safety tip they recommend, along with keeping an eye on traffic in adjacent lanes and behind.

That’s why electronic freeway signs will once again urge drivers to be more aware of motorcyclists, saying: “SHARE THE ROAD. LOOK TWICE FOR MOTORCYCLISTS.”

That message worked in past years, said motorcyclist Les Kurtz, of Fairfield.

“I felt a direct and obvious improvement in the way cars react to me on my motorcycle,” he said of last year’s effort. “More drivers do see me. As proof, I have had fewer cars changing into my lane.”

But not all motorcyclists have the same experience. Albert Rios says he’ll make eye contact with some drivers and then watch as they steer toward him. One time on 19th Avenue in San Francisco, a passenger in a car purposefully flung open his door as Rios passed by.

The survey found that 15 percent of motorcyclists say they have either been hit by a car or hit one. More than 45 percent say they’ve come close to being struck. More worrisome, perhaps: 70 percent say they were racing 10 to 20 mph faster than other vehicles.

Few have sympathy for those who split lanes at high speeds.

“Riding too fast is one of the most common things that motorcyclists do to make lane splitting unsafe,” said safety spokesman Chris Cochran.

Added Patrick Caselli, of San Jose, a motorcycle rider since 1965: “Nothing makes me more angry than some guy flying in and out of traffic at 65-plus.”

Contact Gary Richards at 408-920-5335.