This is a heat dissipating grid installed on a vehicle equipped with dynamic braking where the traction motors are used as generators during braking. The grids act much like an electric toaster, heating as the current is applied to them. They absorb electrical energy generated by the traction motors acting as generators during braking and allow it to be transferred to the atmosphere as heat.. They can be mounted on the roof or under the locomotive or car. Underfloor versions are sometimes fitted with fans (called blowers) to help get rid of the heat.