When that green switch leaks the brakes are applied, and when it lets go at 60 mpg it can be quite unnerving. Then you have to drive off the hiway to get to a safe place to disengage the brake. It is only two small shoes applying pressure to stop a 16,000 lb MH vs 8 shoes or pads in a panic stop using your regular brakes. After going through 3 green switch failures I can see how these brake shoes can wear thin.