Electronically controlled pneumatic brakes are a type of modern railway braking system which offer improved performance compared to traditional pneumatic (compressed air) brakes.
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Traditional systems apply the brakes sequentially from car to car along the train, meaning that up to two minutes can elapse between operation of the control valve on the leading locomotive and the application of brakes on the last car of a 150-wagon freight train.[1] In contrast, ECP braking uses electronic controls which make it possible to activate air-powered brakes on all the wagons throughout the train at the same time. Applying the brakes uniformly and instantaneously in this way gives better train control, shortens the stopping distances, and leads to a lower risk of derailment or of coupling breakage.
During initial testing the ECP equipment had software glitches, and problems from the ingress of moisture into the equipement. These have now been resolved.
Greater intervals between brake tests are also likely because of the ability of ECP brakes to self-diagnose which should generate large cost savings that will help pay for the system to be installed. [2]
The benefits are better control of braking, less equipment wear from pushing and pulling between cars, shorter stopping distance and improved headways.[3]
When first developed, ECP brakes needed a number of wires along the train to control solenoids on each wagon to release the brakes, and were not considered economic for freight. This has changed with the introduction of electronic controls, allowing data to be transmitted by two-conductor wire or radio from the loco to a microprocessor on each car, where locally powered valves hold the desired pressure in each brake cylinder.[1]
ECP can use axle-generated power or wire-distributed power. The Fortescue railway uses wire-distributed power at 200 V DC. The Fortescue line also places the two brake pipes and single control/power cables on one side of the wagons only, as trains operate only as block loads and the wagons are not normally reversed.[4] Having the wires on one side avoids the need for crew to stoop under the coupling, as would be the case with the normal configuration where the hose and wire cross under the coupling.
ECP brakes by the two manufacturers are meant to be mutually compatible.
In the case of the Fortescue railway, the new ECP brakes are incompatible in several ways.
Distributed power is a system where locomotives are coupled in the middle and/or end of a heavy train and remotely controlled originally via radio from the locomotive in the front. Amongst other advantages, this reduces coupling stresses in long and heavy trains. The ECP wiring can also be used to control these intermediate locomotives.
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