Air Brakes and Train Handling Rules - Alaska Railroad

67 Car Equipment and Components67.12.2 Load Proportional Valves and Sensor ValvesSensor valves measure the load condition of a car by measuring truckspring deflection (see Figure 67-G).Figure 67-G. Empty/Load Sensor.Load proportional valves hold brake cylinder pressure on empty carsto lower values during brake applications. The valves direct auxiliaryreservoir air to a small equalizing volume in addition to the brakecylinder. The equalizing volume added to the brake cylinder volumelowers brake cylinder pressure during brake applications on emptycars and reduces the possibility of sliding wheels.67.13 A-1 Reduction Relay ValveSome long cars have an A-1 reduction relay valve that helps transmita service or emergency brake pipe reduction by compensating for theadded brake pipe length of the car (see Figure 67-H).June 1, 1996 ARRC Air Brakes and Train Handling Manual 67-13