Enactment of a trucking deregulation bill passed this month by the Senate Commerce Committee could cut the nation's transportation costs by as much as $8 billion, the Congressional budget office says.

The CBO study concludes that the legislation could cut the Consumer Price Index by 0.3 percent to 0.45 percent and save each of the nation's households $70 to $105 in transportation costs.

Publication of the report, which was requested by the Senate Commerce and Budget Committees, comes at a critical time in the congressional debate over trucking deregulation.

Negotiations are under way to bring the bill introduced by Sens. Howard Cannon (D-Nev.) and Bob Packwood (R-Ore.) to the Senate floor when Congress returns from a recess in mid-April. A House subcommittee considering deregulation is expected to delay consideration of the issue until the Senate completes it works.

The Council on Wage and Price Stability has estimated that a more comprehensive truck deregulation package introduced by the Carter administration and Sen. Edward Kennedy (D-Mass.) could save $5 billion in transportation costs. The CBO study suggests that figure may be conservative, concluding that enactment of the Cannon-Packwood bill could save from $5.3 billion to $8 billion.

The CBO study is based primarily on a review of a number of earlier efforts to analyze the potential economic impact of trucking deregulation. The budget office is an independent research arm of Congress.

The studies include research prepared for the Transportation Department, a number of academic reports and work by other government agencies such as the Interstate Commerce Commission.

In 1978, the regulated trucking industry had revenues of about $36.5 billion, and CBO estimates that those firms would reduce rates by about 15 percent under a deregulation program.

The total impact of deregulation is difficult to measure because of the uncertainty of the effects on the unregulated trucking industry.

The study offers a cautionary note for deregulation advocates, suggesting that the new competition under deregulation could divert traffic from financially strapped railroads.

"This could worsen the financial position of railroads and induce pressures for additional federal aid," the study notes, unless rail deregulation measures are enacted at the same time.

Although the Cannon-Packwood bill does not deregulate the industry immediately or completely, it would ease the entry of new firms into the marketplace and would lift by 1983 the antitrust exemption that allows trucking companies to set prices jointly on single-line hauling.

The regulated trucking industry, represented by the American Trucking Associations, has said that passage of deregulation legislation could result ultimately in higher trucking rates.