Night Mail train dynamic braking on descent from Pattipola to Ohiya: rheostatic grid dissipation?

Descending the steep mountain grade from the railway summit at Pattipola (1,897m) down toward Ohiya and Idalgashinna on the Night Mail train demands continuous dynamic braking to prevent runaway runaway train accidents. Locomotive traction motors are switched to act as electrical generators driven by the descending train wheels. The massive electrical current generated is fed up to forced-ventilated roof resistor grids, where kinetic energy is converted into heat and dissipated into the cold night mountain air. This dynamic electric retardation holds train speed steady at 20 km/h, preventing carriage air brakes from overheating, glazing brake shoes, and losing friction.