Sistema Controllo Marcia Treno

Sistema Controllo Marcia Treno

Sistema Controllo Marcia Treno (SCMT) is a discontinuous train Cab signalling system used in Italy. It shares many features with the Ripetizione Segnali (RS) system, the two systems co-existing and working together. The main purpose of SCMT is to control the respect of the speed limit imposed by the signal aspect and the line condition.

SCMT is divided in two parts:

*SSB: "Sottosistema di bordo" ("Onboard Subsystem")
*SST: "Sottosistema di terra" ("Ground Subsystem")

Working principles

SCMT is based upon an array of transponders called "Punto informativo" (PI from now on) placed on the tracks near signals, reduced speed zones, and other important points along the line. The PIs form the SST . When a train passes over a PI, a set of "antennas" mounted in front of the first boogie energize it through induction. The PI then passes information about the aspect of the next signal through the aforementioned antennas to the SSB.

If the system is supported by RS, and if the signal shows a restrictive aspect (anything different from Green) it has to be acknowledged by the train driver by pressing a button, else the system just gives indication of the signal on its display.

The system then elaborates a "braking curve" (curva di frenatura), that indicates the speed the train has to respect during the approach to the signal, until the "target speed" is reached. Failure of either acknowledging signal aspect or keeping the speed under the imposed braking curve/target speed causes the SSB to command emergency braking, which lasts until the speed gets below the limit.

The SSB takes several variables into account, especially when computing the braking curve, such as:

* Percentage of brake weight (Massa frenata, it measures the overall brake efficiency)
* Maximum speed limit allowed by rolling stock
* Train length
* Steep gradient
* Signal aspect

As said before, SCMT is a discontinuous system; this means that it is not aware of next signals' aspect changes unless it passes upon the relative PIs.

E.g.: if the SSB gets informed by a PI that the approaching signal is "Yellow", it then automatically assumes that the next signal is going to be "Red" and elaborates a braking curve accordingly. But if meanwhile the signal becomes "Green", the SSB does not get aware of it, and it assumes that it is red until the train passes the next PI.

This does not apply if the Ripetizione Segnali (RS) is available (Only when the train is running on a BAcc block type line).In this case the two system work together, and since RS is a continuous system, the SSB is aware of aspect changes, while still appropriately elaborating the maximum speed the train can run.

SCMT has some benefits, in respect of the RS alone:

* is usable on any block type (Italy has different types of block systems in use, and RS is only usable on Automatic Block);
* constantly checks the maximum allowed speed (RS only on the 9 codes version);

However, it has some disadvantages:

* Frequent delays due to the increased rate of emergency brakes intervention, and for the speed limits imposed which stay even if the signals' aspect changes, as said above (especially in case of signal at danger which becomes green);
* Increased stress for the wheels and braking system because of more frequent emergency braking.
* When received on a buffer stop track, in the last 200 m the SSB imposes a speed of 5 km/h; other than the delay this may cause, on certain types of coaches below this speed doors can be opened, thus introducing safety issues.

To partially solve the first two points, the "V-V-V" (stands for "Verde-Verde-Verde") has been introduced. In practice, the distant, protection and departure signals of a station may be encountered by trains showing a green aspect (if some conditions are met), even if the train is scheduled to stop there, and thus is not subjected to speed restrictions imposed by the system.

Description of the SSB


*SCMT: manually activates or deactivates the SCMT function (usually it activates itself automatically as soon as any PI is passed).
*MAN (manovra): sets the SSB on shunting mode.
*RSC (ripetizione segnali continua): activates the RS (ripetizione segnali) system.
*SR (supero rosso): sets the SSB on "Train Trip" mode, used to pass Red signals when needed.
*PRE (prericonoscimento): lights when the train is approaching a "Proceed Slow" signal, if the driver does not press it 12 seconds before receiving an "AC" code (which is received after passing the signal) emergency brakes are applied.
*RIC (riconoscimento): lights when the train is approaching a restrictive aspect signal, if not pressed in 3 seconds, emergency brakes are applied.
*RF (riarmo freno): used to release brakes when the SSB commands emergency brakes.

RIC and PRE keys are used only when RS is also active.

The following table shows the meaning of the signal codes icons used on the display and the target speed the train has to reach according to the braking curve/signal aspect-code.

*Depending on brake efficiency, maximum speed allowed by line and train vehicles.
These speed/signal code values are the same used on Ripetizione segnali.

See also

*Train protection systems
*Cab signalling systems
*Ripetizione Segnali


* [ Italian website "Segnali FS" section about Sistema Controllo Marcia Treno]

External links

* [ Norms about V-V-V]

Wikimedia Foundation. 2010.

Look at other dictionaries:

  • Sistema di Controllo della Marcia del Treno — Bedienungsbildschirm Sistema di Controllo della Marcia del Treno (Abk. SCMT) ist ein Zugbeeinflussungssystem, das im Netz der RFI in Italien eingesetzt wird. Es kann unter ETCS Level 1 laufen und verwendet Eurobalisen zur Datenübertragung… …   Deutsch Wikipedia

  • Sistema di controllo della marcia del treno — Le sistema di controllo della marcia del treno (« système de contrôle de la marche des trains »), souvent abrégé en SCMT, est un système de protection des trains et signalisation en cabine utilisé en Italie. La transmission d… …   Wikipédia en Français

  • Level crossing — This article is about at grade intersections between railway and road. For where two rail lines cross, see level junction. For a type of nuclear receptor (RXR), see Retinoid X receptor. A level crossing at Chertsey, England, as the barriers rise …   Wikipedia

  • Railway signal — Not to be confused with Railway signalling. A signal is a mechanical or electrical device erected beside a railway line to pass information relating to the state of the line ahead to train/engine drivers. The driver interprets the signal s… …   Wikipedia

  • Railway signalling — Not to be confused with Railway signal. A gantry of British semaphore signals seen from the cab of a steam locomotive Railway signalling is a system used to control railway traffic safely, essentially to prevent trains from colliding. Being… …   Wikipedia

  • Token (railway signalling) — A token being offered by a signalman on the Keighley and Worth Valley Railway …   Wikipedia

  • Norwegian railway signalling — The signalling system used on the rail transport in Norway is regulated by the Regulations of December 4, 2001 no. 1336 about signals and signs on the state s railway network and connected private tracks. The first signalling system on the… …   Wikipedia

  • Automatic Train Control — Japanese style ATC indicator. Automatic Train Control (ATC) is a train protection system for railways, ensuring the safe and smooth operation of trains on ATC enabled lines. Its main advantages include making possible the use of cab signalling… …   Wikipedia

  • North American railway signaling — For the actual physical signals, see North American railroad signals. Standards for North American railway signaling in the United States are issued by the Association of American Railroads (AAR), which is a trade association of the railroads of… …   Wikipedia

  • Continuous Automatic Warning System — For the gun, see Heckler Koch HK CAWS. For the wrestling video game creation mode, see Create a wrestler. The Continuous Automatic Warning System (CAWS) is a form of cab signalling and train protection system used in Ireland to help train drivers …   Wikipedia

Share the article and excerpts

Direct link
Do a right-click on the link above
and select “Copy Link”

We are using cookies for the best presentation of our site. Continuing to use this site, you agree with this.