There have been several recent crashes of chinatown-style [1] buses:

In September, four people died after a Megabus driver missed his exit for a depot in Syracuse, N.Y., and smashed into a low bridge on an unfamiliar parkway. Last Saturday, a bus swerved off Interstate 95 in New York City and was sliced in two by a pole, killing 15. On Monday, a bus drove off the New Jersey Turnpike and struck a bridge support, killing the driver and a passenger. -- AP

The article quotes Jacqueline S. Gillan, vice president of the group Advocates for Highway and Auto Safety:

[she] is calling for better safety standards. She urged lawmakers to adopt rules that would require motor coaches of all types to be equipped with seat belts and to have stronger roof-strength standards.

"Motor coach accidents don't happen that often, but when they do happen, they are catastrophic," she said.

Unfortunately, higher physical safety standards for buses would not make travel safer. These bus lines are doing very well (6% growth) mostly because people are taking the bus instead of driving. It's less that they enjoy taking the bus, and more that the buses are really cheap. Even being really cheap, however, they are far safer [2] than private cars. Requiring seatbelts and stronger roofs would be expensive, raising the price of bus tickets compared to cars. This would mean more people would drive instead, and more people would die in traffic accidents.

[1] Buses operating low cost express service between city centers, generally with curbside pickup and dropoff

[2] The problem is that when they crash it is unusual and may kill a bunch of people at once, and so makes the news. Airplanes have this problem too.

Update 2012-11-24: As Julia points out, the government shut down the buses and we, at least, switched to driving.