TheOhNoNotAgainDoes a "10 hour drive" include breaks?
wjriiTo me, it includes breaks to refuel and use the restroom, and if it's more than maybe 6 hours, will factor in the time to scarf down a fast-food meal. Also, any time this discussion involves "X hours" it's undoubtedly being rounded and estimated, and it will involve a hundred different little variables like traffic, road construction, the driver's tolerance for speeding a bit, etc. Also, don't forget that it's common, but not formal, so there's no single way people are taught, and different contexts will require different levels of accuracy.
It’s crazy how big the variables can be as well. Both my ex and I have family in the Baltimore-Washington-Virginia area: for the same trip, she called it a 6.5 hour drive whereas I called it a 9 hour drive. We were both right, with the biggest variable being what traffic in NYC would be like depending on what time each of us liked to start driving