The braking system decelerates a rail vehicle by converting kinetic energy into heat or electrical energy, and must maintain stopping performance under all track and load conditions within defined safety margins.
European rolling stock uses four braking modes — friction, regenerative, magnetic track, and eddy current — often combined in a blended strategy over a pneumatic foundation.
Braking modes
Friction braking acts directly on rotating elements — wheels or axle-mounted discs — through pads or blocks.
Regenerative braking converts the vehicle’s kinetic energy back to electricity through the traction motor; where it cannot be returned to the supply system, it is dissipated in onboard resistors as rheostatic (dynamic) braking instead.
Magnetic track brakes lower an electromagnet onto the rail head; the magnet presses a brake shoe against the rail, and the retarding force comes from friction between shoe and rail, independent of adhesion. They serve as supplementary emergency braking at high speed or on trams, where adhesion is unreliable.
Friction and regenerative braking depend on adhesion; magnetic track braking does not. Brake force calculations covering all modes are governed by EN 14531.
The automatic air brake
The automatic air brake, standardised under International Union of Railways (UIC) leaflet 540, works on the fail-safe principle: a continuous 5 bar pressure in the brake pipe holds the brakes off, and any drop — commanded or from a pipe break — applies them across the train.
Each vehicle carries a distributor valve, a reservoir, and brake cylinders. The system gives long trains a consistent brake response without electronic interconnection, though pressure takes time to propagate along the pipe, producing uneven braking and longitudinal forces.
Electronic brake control sits above the pneumatic system in modern stock, blending friction and regenerative modes and integrating with ETCS brake curves.
Friction braking
Disc brakes are standard on mainline passenger stock above approximately 160 km/h. Cast-iron shoe braking corrugates the wheel tread at wavelengths of roughly 50–80 mm, raising rolling noise; discs also keep braking heat out of the wheel, which matters as speed rises.
Brake discs are alloyed grey cast iron or steel; pad materials are sintered metal or organic composite, selected for thermal capacity, noise, and wear rate.
Cast-iron shoe braking has been phased out across most of the European freight fleet by regulation, not cost: composite (K/LL) blocks now dominate, and Germany and Switzerland banned cast-iron-braked wagons from December 2020. Since December 2024, only Noise TSI-compliant wagons may run on quieter routes.
Wheel slide protection
Wheel slide protection (WSP) is required under TSI LOC&PAS and the TSI for freight wagons (WAG TSI) for defined types, including non-composite-braked units where mean utilised adhesion exceeds 0.12, and disc-braked units. EN 15595 sets acceptance and type-approval criteria but does not mandate fitment, and excludes rubber-tyred and hydraulically braked vehicles.
WSP monitors individual wheelset speed and, as a wheel approaches lock-up, modulates brake pressure to maintain rolling contact and maximise deceleration within adhesion limits. Requirements set a maximum permitted increase in stopping distance relative to ideal adhesion, across defined low-adhesion scenarios.
Magnetic and eddy current brakes
Magnetic track brakes are standard on trams and some regional diesel multiple units. Adhesion-independent braking is required by vehicle authorisation under TSI LOC&PAS point 4.2.4.8 and national rules, not by infrastructure managers’ line conditions.
Eddy current brakes generate retarding force through electromagnetic induction in the rail, without contact, and are used on high-speed trainsets where minimal wheel wear matters. Use outside Germany remains limited chiefly by electromagnetic compatibility with train detection equipment such as axle counters; rail heating has also restricted use on ballasted track to slab-track routes such as Cologne–Frankfurt and Nuremberg–Ingolstadt.