Automakers earned top ratings on head restraints in 45 percent of 2003-model U.S. cars and light trucks, up from three percent when the tests began in 1995, because of improvements in the equipment, an insurer-funded group said. The Insurance Institute for Highway Safety, which evaluated head restraints on more than 200 vehicles in the latest tests, also said those getting the worst grade fell to 10 percent from 82 percent. The four grades range from "good" to "poor." "It used to be that unless you were short, you'd have trouble finding a vehicle with head restraints that extended high enough," Adrian Lund, the Arlington, Virginia-based group's chief operating officer, said in a statement. Now, "in many vehicles, even taller people can position the head restraints to protect the head." The restraints have reduced the severity of whiplash injuries by limiting the movement of passengers' heads in rear-end crashes, the group said. Motorists aren't taking full advantage of the improvements because 80 percent of the equipment must be adjusted manually. The group is planning a study to determine the extent of injury reduction by redesigns of different types of head restraints, spokesman Russ Rader said. Active versions, which automatically adjust to a passenger's height, reduced neck-injury claims 43 percent on vehicles such as the Buick LeSabre sedan, he said.