The U.S. government may have to rewrite bus safety rules because of the growing girth of Americans, USA Today reported Monday.

The Federal Transit Authority (FTA) wants to raise the assumed average weight per bus passenger from 150 pounds to 175 pounds and add an extra quarter of a square foot of floor space per passenger.

The agency says the proposals "acknowledge the expanding girth of the average passenger."

If the changes come into effect, they could mean fewer people will be allowed on city transit buses across the country or force changes to bus designs.

Patrick Scully, from N.Y.-based Daimler Buses North America, said engineers from his company were reviewing the proposals to see how they could alter design.

"This change is really just a bow to reality," said Joseph Schwieterman, from DePaul University in Chicago. "With no small number of bus passengers tipping the scale at 200 pounds or more, this is much more realistic."

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