The agency said the seat belts are an unnecessary expense, the Washington Post reported.
NHTSA, in documents published Thursday in the Federal Register, said large school buses have a fatality rate six times lower than passenger cars. An average of 19 children die each year in bus-related accidents, with 14 of those deaths occurring in bus loading zones.
NHTSA said the deaths are generally from impact with another vehicle or object and that "in such circumstances seat belts will not be effective in preventing the fatality," the newspaper reported.
While small school buses weighing less than 10,000 pounds are required to have shoulder-lap belts, federal safety experts say larger buses are safer because of the padded high-back seats, as well as the tight distance between the rows that means riders in a front-impact crash are projected forward into a cushioned seat back designed to absorb the impact.
In a 2002 NHTSA report to Congress, the agency said that shoulder-lap belts are effective in reducing school bus fatalities but the costs are significant. The addition of the belts would cost $5,485 to $7,346 for each large bus, the agency said.