Actually, I am talking of the VBZ Be5/6 30xx, "Cobra".

This vehicle has 4-wheel running gears. The two wheels on each side are connected to a motor, and it is the control software which makes sure that the speed is accordingly.

The wheels also can swivel, where the angle is mechanically controlled from the articulation.

Actually, it was set up to have sufficient adhesion. But because of the redesign, it got heavier, and it has the highest wheel load of any vehicle ever running on the network (If I remember correctly, even more than the Be4/4 13xx "Elefant" from the early 1930.

There is one issue (which is with all individual wheel configurations): Because there is no axle, there is no self-stabilizing, and there is no even, controlled wear on the wheel profile. This means that such vehicles need more frequent reprofiling. If they wait too long, there will be more and more noticeable vibration (which did lead to the nickname "rattle snake").