This tank mechanic gives more speed after driving for some time.
It is automatic, you don't have to press any buttons.
Overall, if you like badger you may enjoy this tank.
The main purpose is to hold the flank while staying hulldown which is not possible in every game.
I would recommend to play in a heavy line if there is a hulldown position that you can use.
In this position, when played perfectly, this tank is pretty much impenetrable.