BACC

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BACC is a train control system that is installed in Italy on all conventional railway lines with maximum speeds of over 150 km / h in the Ferrovie dello Stato network . The full name is Blocco automatico a correnti codificate , which roughly means automatic route block with coded track circuits .

BACC is a further development of RS4 Codici . The underlying system is used for signaling the driver's cab and requires the driver to acknowledge every change in the signal setting . At BACC, compliance with the specified maximum speed and certain braking curves is also monitored by an on-board computer in the traction vehicle .

There is no data transmission from the locomotive to the control center.

BACC consists of the following parts:

  • Two receiving coils above the rails in front of the first axle of the locomotive or control car
  • A computer-aided vehicle device for decoding the received signals and monitoring the speed specifications
  • A braking group
  • A display and control unit in every driver's cab

Alternating current flows in the rails at a frequency of 50  Hz . An alternating current with a frequency of 178 Hz is superimposed on this . Both currents are modulated with a frequency that depends on the signal position :

Modulation frequency of the 50 Hz carrier signal Modulation frequency of the 178 Hz carrier signal designation meaning
(no) (no) AC
( Assenza di Codice )		 Transmission failure, for example when driving on an inappropriately equipped track in the train station
75 min −1 (no) 75 The next signal shows "Halt", entering a dead end, a partially occupied track or a track with a very short braking distance
120 min −1 (no) 120 The next signal shows a speed limit (to 30 km / h, 60 km / h or 100 km / h)
120 min −1 75 min −1 120 * The next signal shows a speed limit of 100 km / h
120 min −1 120 min −1 120 ** The next signal shows a speed limit of 130 km / h. This code is currently not used.
180 min −1 (no) 180 The next signal shows free travel, but the signal after the next "Stop" or a speed limit. This code is also used to announce the end of the route secured with BACC .
180 min −1 75 min −1 180 * The next signal shows free travel, but the signal after that indicates a speed limit (to 100 km / h or 130 km / h), or a slow driving zone follows with a maximum speed of 150 km / h or less
270 min −1 (no) 270 Free travel at a maximum of 180 km / h
270 min −1 75 min −1 270 * Free travel at a maximum of 220 km / h
270 min −1 120 min −1 270 ** Free travel at a maximum of 250 km / h

The frequency of 50 Hz is also used by RS4 Codici. All codes for which the carrier frequency 178 Hz is not required are used identically with RS4 Codici and BACC. BACC is therefore downward compatible .

The driver is shown the position of the next signal and the speed specification according to the speed code. The system continuously monitors the speed. In the event of excessive speed or if the intended stopping point is not reached, the train is automatically braked.

In the new train control system ETCS , standardized in the EU , BACC is managed as a class B system (Class B system) and is intended to be replaced.

See also

RS4 Codici

Web links