Last month, the Federal Motor Carrier Safety Administration allowed our cameras along while they carried out random inspections at Boston's South Station bus terminal.
One bus was starting to load passengers when DOT Inspector Patty Lavouie stepped in.
Inspectors look for leaks in the engine bay, check treads and tire pressure, and to see if the windows will actually open in an emergency.
They also go through the driver's logbook to make sure he's not driving longer than the legal limit.
They found nothing wrong with this carrier, but in general, safety officials say driver logs are a trouble spot.
"We believe those log books provide too many opportunities for falsification, because again, it's a paper log book," said FMCSA Administrator Anne S. Ferro.
"What's to prevent a driver from literally carrying two sets of books?" asked Greenberg.
"The solution is an electric log, much like an electronic timesheet," said Ferro. "An electric log that ties into the engine of the bus, that identifies whenever that bus is moving, whenever it's being operated by that driver beyond their limits."
Ferro says electronic driver logs could be on buses as early as next year.
Beyond catching sleepy drivers, there are other ways to make bus travel safer. At Penn State's Larsen Institute, researchers working with both private and federal agencies put just about every kind of bus sold in the U.S. through a brutal battery of tests, from big motor coaches to those little airport shuttles.
And where else would you see this? A New York City bus rolling past a dairy farm, on a road designed to mimic the bone-jarring streets of Manhattan.
"The point is that not all buses hold up that well," said Dave Klinikowski, who runs the bus program. "We've had buses that cannot complete the program, or leave the program on a truck, because they've fallen apart."
"So they do make 'em, and you do break 'em?" asked Greenberg.
"We do break 'em sometimes, yes," he replied.
And down the road, buses could get sturdier: Under new federal law, bus companies will look at ways to make roofs less likely to crush, windows less likely to shatter.
Some new buses, like a Greyhound model, already come with seatbelts. But there's no new rule for belts in buses already on the road.
In the 1960s the National Transportation Safety Board made an urgent recommendation to put seat belts in buses.