If last month's epic bus driver fight taught you nothing, let this new video serve as a final lesson -- DO NOT MESS WITH YOUR BUS DRIVER ... because she will beat the crap out of you.
The new video was shot yesterday on board a Baltimore bus -- showing a female bus operator unleashing a ferocious beatdown on a female high school student.
According to the person who posted the clip on YouTube, the fight started because the student was playing her music too loud -- and the bus driver hit FIRST.
At the end of the video, the bus driver says the fight was about the student being "disrespectful."
A rep for the MTA in Baltimore says the driver has worked for the city since 2003, and has been placed on leave while the MTA investigates the incident.
It's the second crazy fight video we've seen on a bus in a month -- you'll recall the last video showed a male bus driver in Cleveland uppercutting a girl for allegedly assaulting him (below).
**WARNING -- VIDEO CONTAINS REALLY BAD LANGUAGE**