Originally Posted by Web Foot STi
If those "chains" are anything like what the school busses around here use it's an octopus like head that moves down and puts the arms into the interface between the tyre and the snow/ice. The "chains" never are on the tyre/wheel in the conventional sense. They seem to work well on an on demand basis for busses. Not piratical for a passenger car retrofit.
Yes, they just spin and fall between the tire and road to provide traction. They are permanently attached to the bus.