Fewer than half of all U.S. children wear helmets while biking, skating and riding scooters, a survey by safety researchers said on Tuesday.

Many children observed in the survey who were wearing helmets were wearing them improperly, leaving them vulnerable to Head injury, the nonprofit Safe Kids campaign found.

The researchers found that helmet use was lowest on residential streets, although that is where most accidents occur because that is where children play most frequently. Only 33 percent of children watched on residential streets were using helmets, the campaign said.

But in states with mandatory helmet laws, 45 percent of child bikers were seen wearing helmets, as opposed to 39 percent in states with no helmet laws.

“Head injuries are preventable, and there are relatively simple steps people can take to ensure a safer ride,” Angela Mickalide, program director for Safe Kids, said in a statement.

“Most parents and kids don’t understand just how fragile the brain is, and that a fall from a little as two feet (less than a meter) can cause a skull fracture.”

The report cited statistics showing more than 70 percent of U.S. children aged 5 to 14, or 27.7 million children, ride bicycles. Many also ride skateboards, scooters and skates, especially inline skates.

“Bicycles are associated with more childhood injuries than any other consumer product except the automobile,” the report reads.

“In 2001, 134 children ages 14 and under died and nearly 314,600 were injured in bicycle crashes. Additionally, more than 176,000 children ages 5 to 14 are treated each year in hospital emergency rooms for injuries related to skateboards, scooters and skates.”

Helmets reduce the risk of brain injury in a bike accident by 88 percent, they said, and head injuries account for up to 80 percent of bike fatalities.

In autumn 2003, Safe Kids researchers watched more than 8,000 children and nearly 1,400 adults at 549 sites in 46 states and the District of Columbia.

They said their study was not nationally representative, but gave a taste of the habits of U.S. children and parents.

They saw 3,739 children, or 41 percent of the total, wearing helmets. Just 39 percent of the adults did.

And nearly a third, or 35 percent, of child riders who wore helmets wore them improperly, with helmets tilted or straps unsecured, they said.

The campaign said helmets should be level on the head, and fit firmly with the chin strap snug and forming a “V”