Regenerative braking, traction / stability control, ABS question

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Check to see if there is a recall on your vehicle using your VIN # to verify that exact issue.

 

yes, road imperfections activate safety systems, because they don't know that it isn't something dangerous.
can make your heart skip a beat though.

 

No, it's the ABS/brakes kicking in and cancelling regen. There's a momentary surge/lurch feeling during the transition and Toyota's software (G2&3 not sure about 4) isn't the best at it. It's a FAQ. I can do it at will in my 2006 at a major intersection with a bumpy railroad track crossing in the slow down zone.

 

It's definitely the ABS taking over and releasing braking action momentarily, and it would not matter if you were in the friction braking zone or simply in the regen zone. When the wheels rise over the bump, they lose a bit of traction (less contact with the pavement) causing them to slow down in relation to the vehicle speed. This is interpreted as loss of grip (skidding if you will) and the ABS releases brake action to allow the wheels to speed back up to vehicle speed. In theory, this will happen to any car with ABS, but seems to affect the Prius more than most, probably due to the complexity of managing regen braking combined with friction braking.