Automobile safety belts are effective in cutting deaths and injuries by roughly half, Congress' investigative agency concludes after reviewing a series of studies.

The General Accounting Office's report coincided with the launching Monday of a renewed Transportation Department campaign to persuade all 50 states to pass seat- belt laws and to enforce belt use.The GAO said 11 recent studies varied greatly in pinpointing the effectiveness of safety belts in reducing fatalities, ranging from 41 percent to 94 percent.

"But most of the estimates clustered in the range of 50 percent to 75 percent," it said and added: "The consistency and relatively narrow range of estimates provides strong evidence of safety-belt effectiveness."

The report said eight studies on injury reduction attributed to the use of seat belts ranged from 17 percent to 88 percent, but "most of the estimates clustered in the range of 44 percent to 66 percent."

Four studies reviewed by the GAO examined the effect of seat-belt use on hospital admissions, examining the hospitalization rate for belted and unbelted vehicle occupants.

"Hospital admission rates for belted occupants were 56 percent to 74 percent lower than for unbelted occupants," the GAO said.

The Transportation Department has encouraged states to pass mandatory auto seat-belt laws but has not required them.

Thirty-eight states and the District of Columbia have belt laws.