WASHINGTON — States should require motorcycle riders to wear proper helmets, government investigators urged yesterday as part of several recommendations that seek to stem a steady rise in motorcycle deaths.

Members of the National Transportation Safety Board unanimously approved the motorcycle safety recommendations.

"The simple act of donning that helmet can begin the process of preventing that type of fatality and serious injury," said NTSB Chairman Mark V. Rosenker.

In 2006, motorcycle deaths increased for the ninth straight year, to 4,810 motorcycle deaths, compared with 4,576 in 2005.

NTSB officials noted that non-helmeted riders were three times more likely to suffer a brain injury in a crash than those wearing a helmet.

In Hawai'i, helmets are required only for operators or passengers of motorcycles who are younger than 18, according to the Insurance Institute for Highway Safety.