More drivers are crashing on Idaho's roads, but fewer people are being killed or injured, a state study says.

Seat-belt use in Idaho is increasing while injuries and fatalities are declining, according to a traffic accident analysis of 1989 released Friday.The numbers suggest that Idaho's mandatory seat-belt law is working, said Pat Raino, a traffic safety specialist for the Idaho Department of Transportation.

"There has been just a steady decline in the rates," Raino said. "That's real gratifying to see that."

Although the number of accidents in the state increased in 1989, the number of severe accidents that caused a death or injury was lower last year than in any year in the 1980s, the study says.

Seat-belt use, meanwhile, has doubled since legislators made it illegal in 1986 to drive or ride in the front seat of a car without wearing one.

More than a third of drivers obey the law, a rate Raino said is dismally low but still twice as high as the percentage before the law went into effect.

Increased use of seat-belts helped reduce the number of fatalities to 238 people last year, a 7 percent decrease from the previous year, the study says. The number of traffic injuries declined 3 percent.

The declines came despite a 4-percent increase in the total number of accidents, which totaled 22,101 last year.

In addition to the seat-belt law, auto manufacturers and highway improvement projects could have reduced the number of debilitating accidents, Raino said.

Automakers are installing anti-lock brakes on more models than in previous years and are strengthening roofs to prevent collapse in rollover accidents, she said.

Highway improvement projects include the widening of roads, removal of barriers that block drivers' vision and installation of signs warning of hazards, she said.

Among the findings in the 48-page report:

- The total economic loss of traffic accidents in Idaho, including property damage and the loss of wages, totaled more than $340 million last year.

- Twenty-five percent fewer motorcyclists were involved in accidents in 1989 than in 1986.