Them’s the brakes.

A Saskatoon Transit bus was left empty and rolling down a city block Tuesday night after the driver ditched the bus to take a bathroom break, the transit service says.

The bus, which was left at a designated stop at Millar Avenue and 51st Street at about 8:25 p.m., travelled about one block before becoming stuck on a rock. The driver had exited the bus for a restroom break.

No passengers were on the bus and no other vehicles were hit, according to Saskatoon Transit.

The incident is under investigation.