Cheap fares, some as low as a dollar, have drawn millions of passengers to Megabus. On Sunday, one of its buses went up in flames outside of Chicago. Everyone got out safely, but this was not an isolated incident.
The fire began with a blown tire before flames engulfed the bus.
"It was horrifying, everybody running down the highway, it was terrible," one passenger said.
It wasn't the New Jersey-based company's first brush with tire-related disasters. In 2012, a 25-year-old graduate student in Illinois was killed in a crash allegedly caused by a blown tire. Forty-seven passengers were hospitalized.
There have been at least five other incidents involving blown tires on Megabuses, including one in 2014 that caused the bus to slam into a guard rail on I-95.
At least one lawsuit has been filed claiming there's a problem with the buses carrying too much weight. Clarence Ditlow with the Center for Auto Safety explained how weight affects the tires.
"If a bus is overweight, in a worse-case scenario the tires can rub against the wheel well which generates friction, heat, and ultimately a fire."
In the last 24 months, safety inspectors found 29 maintenance violations considered an imminent hazard to Megabus drivers or passengers. Megabus says it carries 10 million people a year in its fleet of 275 buses.
The company released a statement saying "safety continues to be our top priority and Megabus.com is fully cooperating with the authorities."
The federal agency that oversees bus travel issued an advisory about overloaded buses in 2012, but Ditlow says that's not enough.
"If one of these buses had been in heavy traffic before it could pull off to the side of the road, it might have been a catastrophic fire before the people could get out of the bus to safety."
Ditlow also says the buses are weighed to make sure they comply with safety limits, but that happens before they're loaded with passengers and baggage.