How many hours can a bus driver drive in a day?

According to the FMCSA, bus drivers are allowed to drive 10 hours after eight consecutive hours off duty. There’s no limit to how many of the 10 hours can be driven consecutively; drivers can drive for as little as a few minutes or as much as 10 hours in a row. 

Here’s an example: 

You’ve had eight consecutive hours off. After arriving to work at 7 a.m., you begin driving at 8 a.m. and complete your driving at 6 p.m. You can’t drive again until you take another eight consecutive hours off. You can, however, perform other work duties after 6 p.m., but driving a commercial vehicle is prohibited.