Fahrsperre
Mechanische Fahrsperre (Streckenanschlag)
Trackside trip arm physically triggering emergency braking if a train passes a danger signal (Red).
Easy
Based on vigilance required, reaction window, and braking penalty severity.
menu_book System Overview
The Fahrsperre (also known as Streckenanschlag or mechanical train stop) is the foundational safety system utilized in German rapid transit networks, most notably the Berlin U-Bahn, Berlin S-Bahn, and Hamburg U-Bahn. It employs a physical tripcock arm mounted next to the running rail mechanically interlocked with line signals. If a signal indicates Halt (Red), the trip arm is raised in the path of the train. Should a train overrun the signal, the arm strikes a tripcock lever under the train carriage, venting the main air brake pipe directly to the atmosphere and applying instant emergency braking.
settings How It Operates
- check_circle At Red / Halt Signals: The trackside mechanical trip arm is raised in an upright position alongside the rail.
- check_circle Signal Overrun (SPAD): If the train passes a red signal, the raised trackside arm hits the train's mechanical tripcock lever (Auslösehebel / Notbremshahn) mounted near the bogie.
- check_circle Instant Emergency Braking: Striking the lever mechanically opens the main brake pipe (Hauptluftleitung), venting air pressure immediately and clamping the emergency brakes until a full stop.
- check_circle At Green / Proceed Signals: The arm is rotated down flush with the rail by an electric motor or pneumatic actuator, allowing the train to pass unobstructed.
- check_circle Trip Reset: After an enforced stop, the driver must wait for the train to come to a standstill, reset the tripcock brake valve, and obtain dispatcher permission to resume.
visibility In-Cab Visual & Audio Indications
Loud acoustic rush of air as the brake pipe vents into the tunnel.
Main brake pipe pressure gauge drops to 0 bar while cylinder pressure climbs to maximum.
Red indicator illuminates on the cab console indicating emergency trip activation.
lightbulb Driver Tips to Avoid Penalty Brakes
- verified Always observe distant and repeater signals in tunnel curves: emergency stops triggered by the Fahrsperre are instantaneous and violent.
- verified In SubwaySim Berlin (Line U4) and SubwaySim Hamburg (Line U3), the Fahrsperre is active along all main tracks together with Sifa.
- verified Stop comfortably before signal stop boards (Haltetafel / Sh0) to avoid any contact with the mechanical arm.
