The Federal Motor Carrier Safety Administration reminded bus carriers to check their tires Thursday following two incidents involving Megabus coaches which officials initially blamed on blown tires.
"A tire on a motor coach loaded beyond its weight rating, operated at highway speeds for a significant period of time, is more likely to overheat and fail," the agency's statement said.
Double-decker buses pose an extra potential risk because of their heavier loads, loads that at times could stress bus tires beyond the weight they are designed to carry, according to the statement.
A Missouri University graduate student died after a double decker bus she rode in earlier this month crashed into concrete overpass support. Investigators initially blamed that crash on a tire blowout.
The next week, a motor coach in Georgia caught fire because of what investigators initially suspected was a blown tire.
Both of the buses carried heavy loads and operated on very hot days, authorities said. Those two factors put additional stress on the tires.
The agency also recommended bus operators monitor the loading of the buses, ensuring weight in terms of both cargo and passengers is distributed properly to prevent overloading the tires.
A fully loaded motor coach could exceed weight limits or tire weight ratings, officials said.
Companies "that violate tire loading restrictions may be declared an imminent hazard and immediately be placed out-of-service," the statement said.