[T.B. Yoits]

There's a lot of ballast in those tow tractors. It would take a significant event to flip one.

If it was an aircraft tug. The article is poorly written but I suspect it was a baggage cart tug, not an aircraft tug, because ramp workers flip baggage cart tugs surprisingly frequently.

Aircraft tug drivers, when they crash (and they do), usually crash into the aircraft itself, not the bridge or other vehicles.

[Mr.Unique]

Aircraft tug drivers, when they crash (and they do), usually crash into the aircraft itself, not the bridge or other vehicles.

Or sometimes they hit the gas instead of the brake in the equipment yard and run into a hydraulic mule. Ask me how I know. ;)