Once got subbed out to another depot for a month or so...they decided to only allow me to learn one route. It was a circular route from a town centre stop, not the bus station. You only had about 10 - 15 minutes standing time before the next trip. However you were out for about 9 hours, but no actual lunch break. It was calculated that the standing time accrued to allow a sufficient rest period....
The only way to get a 'comfort break' was to drop a run...drive round to the bus station and be quick about it.... I had my fair share of run-ins with the traffic regulator when i turned up for a pee... I think my colourful use of anglo-saxon language to explain that i wasn't spending all day without a 'comfort break' eventually made them change their mind and let me route learn other town services too.
Once back at my home depot and on the regular service i drove on a daily basis for the last few years (1h 35m trip) i always found time to take a 'comfort break' at the terminus before departing again; oh and you had to pass the coffee machine in the messroom as well.