TECHNICAL FIELD OF THE INVENTION

The present invention relates to a ventilation system for tunnels of transportation networks on fixed guideway, such as railways.

In particular, the present invention is advantageously, but not exclusively, applicable to the field of underground railway systems, to which, for the sake of convenience, the following description specifically refers but without any loss of generality.

PRIOR ART

As is known in the prior art, underground railways are provided with ventilation systems that, in the event of a fire in a tunnel, caused by a train or by other conditions, essentially have the function of extracting the smoke from the tunnel and protecting the passengers' routes of escape .

The ventilation systems for underground railway systems currently in use comprise shafts, which are very expensive and technically challenging structures, installed in the stations and/or along the tunnels, and which are referred to in this description as air shafts, and fans configured to extract and blow air. Generally speaking, with the ventilation systems currently in use, in the event of a fire the fans are activated to extract the smoke from the area in which the fire has broken out and vent it to the outside by- conducting it through the air shafts.

In particular, in the event of a fire breaking out at a station, the fans installed in the station are activated so that the smoke is extracted from the station and vented to the outside through the air shaft in the station in order to protect the evacuation of passengers and staff from the station. In the event of a fire breaking out in a tunnel, the fans installed in the tunnel are activated so that the smoke is extracted from the tunnel and vented to the outside through the air shaft in the tunnel in order to protect the evacuation of the passengers and staff from the tunnel .

A further example of the functioning of the ventilation systems currently in use is provided below. In particular, in the event of a fire breaking out in a tunnel, the fans are activated to enable evacuation "upwind" of any people in the tunnel where the fire has broken out, i.e., given the two air shafts closest to the fire, the smoke is vented to the outside through one of the two air shafts while fresh air is blown into the tunnel through the other air shaft. OBJECT AND SUMMARY OF THE INVENTION

The Applicant has noticed that the ventilation systems of the type currently in use have characteristics that, in certain conditions, can result in lack of protection for passengers.

Due to the structure of the ventilation systems currently in use, the smoke generated by a train on fire in a tunnel also flows into areas other than the site of the emergency. There could be passengers or railway staff in these areas who would therefore be put at risk.

In this connection, figures 1 and 2 show two emergency scenarios in which the ventilation systems currently in use are ineffective.

In particular, figure 1 shows a first scenario in which a fire has broken out on board a first train 11 in a two-track single-tube tunnel 12. The first train 11 is coming from the station 13 which is provided with an air shaft 14, while the tunnel 12 is also provided with a respective air shaft 15 arranged about half way along the tunnel 12, between the station 13 and the next station (not shown) . The first train 11 that is on fire has stopped in the tunnel in a position A. A second train 16 arriving on the other track has stopped in a position B, in that, since the first train 11 is on fire and has stopped, traction power has been deactivated. Or, similarly, the second train 16 is following the first train 11, which in this case is travelling towards - A -

the station 13, and stops in the position B again because, due to the fire, traction power has been deactivated.

The ventilation system controls the airflows to enable evacuation "upwind" of the passengers of the train 11 on fire towards the station 13.

In other words, as shown, for example, in figure 1, the fans (not shown) are activated so that the smoke, indicated by the letter F, is extracted from the tunnel 12 and vented to the outside through the air shaft 15, while fresh air is blown into the tunnel 12 through the air shaft 14.

In figure 1 the arrows indicate the direction of the airflow produced by the ventilation system. The hot smoke F, carried by the airflow generated by the ventilation system, fills the tunnel 12 behind the first train 11 that is on fire and engulfs the second train 16, which has stopped in the position B. If the position B is some distance from the air shaft 15, beyond which there is an area of cooler, clean air, the passengers could be suffocated by the heat of the smoke F and/or the toxic fumes generated by the fire before they manage to get beyond the air shaft 15.

It is important to remember that, in the event of a fire in a railway tunnel, the temperature can rise to well above 50° C within 5-10 minutes after the outbreak of the fire and lethal levels of carbon monoxide (CO) occur after about 10 minutes.

Inverting the direction of the airflow would create a single safe direction of evacuation for the occupants of both trains 11 and 16, but would carry the hot smoke

F into the station 13.

Moreover, during transient times the smoke could change direction, causing confusion among the passengers and creating dangerous situations. Figure 2 shows a second scenario in which a fire has broken out in a central carriage, indicated by letter B, of a train 21, which is a train made up of three carriages, indicated, respectively, by letters A, B and

C. The train 21 is in a one or two-track single-tube tunnel 22 and is coming from, or travelling towards, a station 23.

The station 23 is provided with an air shaft 24, and the tunnel 22 is also provided with a respective air shaft 25 arranged about half way along the tunnel 22, between the station 23 and the next station (not shown) . As in the previous scenario, in this case the ventilation system is also activated and directs the airflow from the air shaft 24 towards the air shaft 25, as indicated by the arrows in figure 2. The passengers in the carriage A can, thus, be evacuated in safety "upwind" , while in order to get to the area where the air is clean and cooler, the passengers escaping from part of the carriage B and the carriage C would have to go through the carriage B, where the fire has broken out and the air is full of smoke and hot. The passengers escaping the fire would be unlikely to proceed towards the carriage A, even if directed, also because it might be impossible for them to pass through or alongside the burning carriage B.

Therefore the passengers from part of the carriage B and from the carriage C would probably go the opposite way, in the same direction as the airflow and, thus, as the toxic fumes and high temperatures indicated in figure 2 by letter F.

The distance between the carriage C and the safe area, which is beyond the extraction air shaft 25, could thus be too great to allow the passengers to escape before the toxic fumes and heat reach lethal levels .

Therefore the purpose of the present invention is to provide a ventilation system for railway tunnels that overcomes the drawbacks described above.

Said purpose is achieved by the present invention, which relates to a ventilation system for a fixed- guideway-based transportation network as defined in the appended claims. BRIEF DESCRIPTION OF THE DRAWINGS

In order to better understand the present invention, some non- limiting preferred embodiments thereof will now be described by way of example with reference to the accompanying drawings (not all to scale) in which:

Figure 1 shows a first emergency scenario in which a fire has broken out on board a train in a railway tunnel;

Figure 2 shows a second emergency scenario in which a fire has broken out on board a train in a railway tunnel; and - Figure 3 shows a first scenario of use of a ventilation system according to the present invention;

Figure 4 shows a second scenario of use of the ventilation system according to the present invention;

Figure 5 shows a third scenario of use of the ventilation system according to the present invention;

Figure 6 shows a fourth scenario of use of the ventilation system according to the present invention,- and

Figure 7 shows a block diagram of the ventilation system according to the present invention.

DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS OF THE INVENTION

The following description is provided to enable an expert in the field to implement and use the invention. The expert in the field will be able to implement various modifications to the embodiments described herein and the general principles disclosed herein could be applied to other embodiments and applications without departing from the scope of the present invention.

Therefore the present invention is not to be limited in scope to the specific embodiments described and illustrated herein, but is to be accorded with the widest scope consistent with the principles and features disclosed herein and defined in the appended claims.

In particular, the present invention is described below, merely by way of a non- limiting example, with specific reference to a railway network, conveniently an underground railway, on which trains travel, while it is understood that the present invention is applicable to any type of fixed-guideway-based transportation network on which a generic vehicle travels.

Unlike the ventilation systems currently in use, in which the smoke and hot air generated by a fire are extracted and vented to the outside at a single point along the railway line, i.e. in correspondence with an air shaft, often being conducted through areas that are not affected by the fire, a ventilation system according to the present invention extracts the smoke and hot air locally, i.e. it extracts the smoke and hot air from the tunnel or from the station where the fire has broken out in proximity to the actual fire and pipes them, through a specific conduit, to the point at which they are - in ¬

vented to the outside. This prevents the risk of the smoke and hot air flowing through areas not affected by the fire and creating a hazard for any people in said areas . The ventilation system according to the present invention extracts the smoke and hot air generated by a fire locally, that is in the area in which the fire has broken out, and directs them through a specific conduit that carries them to the outside. In particular, the ventilation system of a railway tunnel and/or of a station according to the present invention comprises an air duct, conveniently housed in the roof of the tunnel and/or of the station. A vacuum is created in the air duct by specific suction means coupled to the air duct, for example of the electromechanical type and arranged at one end of the air duct . The air duct comprises a series of apertures, hereinafter referred to as air vents, that, when open, connect the inside of the air duct with the inside of the tunnel or station and which in the idle condition are closed by respective opening/closing devices, for example gate valves, which are opened automatically by the ventilation system in relation to the site of the fire. The smoke and hot air are only extracted through the open air vents.

Conveniently, the air duct can be sectioned, either dynamically, for example by means of electrically actuated airlocks, or statically, for example by means of bulkheads .

Figure 3 shows an example of the functioning of the ventilation system according to the present invention in a tunnel in which a fire has broken out.

In particular, as shown in figure 3, in a tunnel 31 provided with a ventilation system according to the present invention, a fire has broken out on board a train 32. As stated previously, the ventilation system comprises an air duct 33 housed in the roof of the tunnel 31 and in which a vacuum has been created by specific suction means (not shown) coupled to the air duct 33. Said air duct 33 comprises a plurality of air vents 34 that, when open, connect the inside of the air duct

33 with the inside of the tunnel 31 and when idle are closed by respective opening/closing devices (not shown) . When the fire is detected by specific fire detecting means (not shown) installed along the railway line and on board the train 32, the ventilation system opens the air vents 34 in proximity to the fire and the smoke and hot air, indicated in figure 3 by letter F, are extracted from the tunnel 31 through said open air vents

34 and piped and carried out through the air duct 33. In figure 3 white rectangles are used to indicate the open air vents 34, while black rectangles are used to indicate the closed air vents 34.

Moreover, also in figure 3, an arrow indicates the direction in which the hot air and smoke F flow in the air duct 33.

Moreover, the ventilation system according to the present invention preferably also comprises, for each station and/or for each tunnel, a manufactured structure connecting with the outside, that is, in accordance with commonly accepted building practice, a structure of moderate technical complexity. Each manufactured structure connecting with the outside connects the air duct, preferably housed in the roof of the station or tunnel, with the outside of the station or tunnel.

According to the present invention the manufactured structure connecting with the outside can consist of any manufactured structure that connects the station or the tunnel with the outside, even if it is smaller than a conventional air shaft, for example a cavity or light well, thus overcoming the need to implement expensive and technically challenging air shafts, as is the case with the ventilation systems currently in use.

It is clear that the ventilation system according to the present invention can also conveniently be used with a conventional air shaft to provide the connection with the outside.

In the idle condition the manufactured structures connecting with the outside could conveniently be closed by means of respective opening/closing devices, for example gate valves, opened automatically by the ventilation system in relation to the site of the fire.

Moreover, the air duct is coupled to ventilation means, for example fans, configured to extract and blow air. Said ventilation means are automatically actuated by the ventilation system in relation to the site of the fire .

The ventilation means can conveniently be used to create the vacuum in the air duct, instead of the specific suction means described previously. Moreover, the ventilation means can be distributed along the air duct, coupled to each air vent, or located in correspondence with the manufactured structures connecting with the outside .

Figure 4 shows another example of the functioning of the ventilation system according to the present invention.

In particular, as shown in figure 4, a fire has broken out on board a train 42 in a tunnel 41.

According to the present invention, a ventilation system for the tunnel 41 comprises an air duct 43 housed in the roof of the tunnel 41 and coupled to ventilation means (not shown) configured to create a vacuum in the air duct 43 and conveniently distributed along the air duct 43.

Said air duct 43 comprises a plurality of air vents

5. 44 that, when open, connect the inside of the air duct

43 with the inside of the tunnel 41 and that, in the idle condition, are closed by respective opening/closing devices (not shown) .

Moreover, the tunnel 41 is provided with a0 manufactured structure connecting with the outside 45 that connects the air duct 43, housed in the roof of the tunnel 41, with the outside of the tunnel 41.

When the fire is detected by specific fire detecting means (not shown) installed along the railway line and5 on board the train 42, the ventilation system opens the air vents 44 in proximity to the fire and activates the ventilation means to extract air through the air duct 43. In this way the smoke and hot air, indicated in figure 4 by the letter F, are extracted from the tunnel0 41 through the open air vents 44, they are piped and made to flow through the air duct 43 to the manufactured structure connecting with the outside 45 and, ultimately, vented to the outside through the manufactured structure connecting with the outside 45. 5 As in figure 3, in figure 4 white rectangles are used to indicate the open air vents 44, while black rectangles are used to indicate the closed air vents 44. Moreover, also in figure 4, the black arrows indicate the directions of the flow of hot air and smoke F in the air duct 43 and in the manufactured structure connecting with the outside 45, while the white arrows indicate the flow of fresh air induced by the suction pressure created when the air vents 44 in proximity to the fire are opened.

Figure 5 shows another example of the functioning of the ventilation system according to the present invention.

In particular, as shown in figure 5, a fire has broken out in a tunnel 51 on board a train 52 coming from or travelling towards a station 53. According to the present invention, a ventilation system for the tunnel 51 and for the station 53 comprises an air duct 54 housed in the roof of the tunnel 51 and of the station 53.

Said air duct 54 comprises a plurality of air vents 55 that, when open, connect the inside of the air duct

54 with the inside of the tunnel 51 and of the station

53 and that in the idle condition are closed by respective opening/closing devices (not shown) .

Moreover, the tunnel 51 is provided with a manufactured structure connecting with the outside 56 preferably arranged about half way between the station 53 and the next station (not shown) . The manufactured structure connecting with the outside 56 connects the air duct 54, housed in the roof of the tunnel 51, with the outside of the tunnel 51 and is provided with respective ventilation means (not shown) configured to extract and blow air.

The station 53 is also provided with a respective manufactured structure connecting with the outside, indicated in ^" figure 5 by number 57. The manufactured structure connecting with the outside 57 connects the air duct 54, housed in the roof of the station 53, with the outside of the station 53 and is provided with respective ventilation means (not shown) configured to extract and blow air. The ventilation means of the manufactured structures connecting with the outside 56 and 57 are configured to create a vacuum in the air duct 54.

When the fire is detected by specific fire detecting means (not shown) installed along the railway line and on board the train 52, the ventilation system opens the air vents 55 in proximity to the fire and activates the ventilation means of the manufactured structure connecting with the outside 56 so that they extract air through the air duct 54. In this way the smoke and hot air, shown in figure 5 by the letter F, are extracted from the tunnel 51 through the open air vents 55, they are piped and made to flow through the air duct 54 to the manufactured structure connecting with the outside 56 and, ultimately, vented to the outside through the manufactured structure connecting with the outside 56. As in figures 3 and 4, in figure 5 white rectangles are used to indicate the open air vents 55, while black rectangles are used to indicate the closed air vents 55. Moreover, also in figure 5, black arrows are used to indicate the directions of the flow of hot air and smoke F in the air duct 54 and in the manufactured structure connecting with the outside 56, while white arrows are used to indicate the flow of fresh air induced by the suction pressure created when the air vents 55 in proximity to the fire are opened. Conveniently, the ventilation system can also include line aerating means comprising, for instance, one or more fans, distributed along the railway line and configured to blow air along the railway line in order to create a push-pull condition with the extraction of smoke and hot air F and thus boost the flow of fresh air, indicated by the white arrows in figures 4 and 5, and, thus, the extraction efficiency of said ventilation system.

In particular, said line aerating means can conveniently be housed in respective ventilation chambers obtained in the stations, for example at the ends of the stations, and/or in specific seats obtained in the slab supporting the rails and/or in the walls of the tunnels.

As an alternative to the line aerating means, the ventilation system could conveniently use the ventilation means coupled to the air duct and installed in the sections of the railway line adjacent to that in which the fire has broken out to blow air along the railway line in order to create a push-pull condition in the event of a fire.

In the event of fire, the ventilation system could open the air vents of the air duct in correspondence with ventilation means present in the sections of the railway line adjacent to that where the fire has broken out, and activate said ventilation means so that they blow air along the railway line through said open air vents .

Another example of the functioning of the ventilation system according to the present invention is shown in figure 6.

In particular, as shown in figure 6, a fire has broken out on board a train 64 in a tunnel 61, between two stations, indicated respectively in the drawing by numbers 62 and 63. According to the present invention, a ventilation system for the tunnel 61 and the stations 62 and 63 comprises an air duct 65 housed in the roof of the tunnel 61 and of the stations 62 and 63.

Said air duct 65 comprises a plurality of air vents

66 that, when open, connect the inside of the air duct 65 with the inside of the tunnel 61 and of the stations

62 and 63 and that when idle are closed by respective opening/closing devices (not shown) .

The tunnel 61 is also provided with a manufactured structure connecting with the outside 67 arranged about half way between the station 62 and the station 63. The manufactured structure connecting with the outside 67 connects the air duct 65, housed in the roof of the tunnel 61, with the outside of the tunnel 61 and is provided with respective ventilation means (not shown) configured to extract and blow air.

The stations 62 and 63 are also provided with respective manufactured structures connecting with the outside indicated respectively in figure 6 by numbers 68 and 69. The manufactured structures connecting with the outside 68 and 69 connect the air duct 65, housed in the roof of the stations 62 and 63, with the outside of the stations 62 and 63 and are provided with respective ventilation means (not shown) configured to extract and blow air. The ventilation means of the manufactured structures connecting with the outside 67, 68 and 69 create a vacuum in the air duct 65.

When the fire is detected by specific fire detecting means (not shown) installed along the railway line and on board the train 64 , the ventilation system opens the air vents 66 in proximity to the fire and activates the ventilation means of the manufactured structure connecting with the outside 67 so that they extract air through the air duct 65. In this way the smoke and the hot air, indicated in figure 6 by the letter F, are extracted from the tunnel 61 through the open air vents 66, they are piped and made to flow through the air duct 65 to the manufactured structure connecting with the outside 67 and, ultimately, vented to the outside through the manufactured structure connecting with the outside 67.

As in figures 3, 4 and 5, in figure 6 white rectangles are used to indicate the open air vents 66, while black rectangles are used to indicate the closed air vents 66. Moreover, also in figure 6, black arrows are used to indicate the directions of the flow of hot air and smoke F in the air duct 65 and in the manufactured structure connecting with the outside 67, while white arrows are used to indicate the flow of fresh air induced by the suction pressure created by opening the air vents 66 in proximity to the fire and the push-pull condition caused by the air being blown along the railway line by the line aerating means, if present, or by the ventilation means coupled to the air duct 65 and installed in the sections adjacent to that where the fire has broken out, specifically activated as blowing fans by the ventilation system.

With regard to the case in which air is blown by the ventilation means coupled to the air duct 65 and installed in the sections adjacent to that where the fire has broken out, the air duct 65 is sectioned so that the air is actually blown along the railway line and not inside said air duct 65.

The air duct 65 is preferably sectioned dynamically by means of bulkheads that are opened and closed by the ventilation system depending on the site of the fire.

Below is a description of how the ventilation system according to the present invention monitors the trains, tunnels, stations and the railway line in general in order to detect a fire and sets about eliminating the smoke, toxic fumes and hot air and thus protect the routes of escape of the passengers and railway staff.

Figure 7 is a block diagram of a ventilation system 70 according to the present invention.

In detail, as shown in figure 7, the ventilation system 70 according to the present invention comprises on-board fire detecting means 71 installed on board each train and configured to detect a fire on board the respective train.

Preferably, said on-board fire detecting means 71 can comprise smoke and temperature sensors, conveniently of the analog addressable type, for instance, rate-of- rise detectors, and/or can be installed both in the passenger compartment and in the technical compartments, including the under-chassis .

Moreover, the ventilation system 70 comprises on- board communication means 72 installed on board each train, coupled to the on-board fire detecting means 71 and configured to send the data acquired by the on-board fire detecting means 71 to an electronic control unit 73 of the ventilation system 70. Preferably the on-board communication means 72 can comprise a two-way communication device also configured to receive data from the electronic control unit 73, and/or can be based on wireless technology, for instance Wi-Fi. Moreover, if the on-board fire detecting means 71 are of the analog type, said on-board fire detecting means 71 are coupled to the on-board communication means 72 using an analog/digital converter (not shown) .

Moreover, the ventilation system 70 can conveniently also comprise line fire detecting means 74 distributed along the entire railway line, in the stations and in the tunnels and configured to detect a fire along the railway line and also to provide information about the position on the railway line at which they are installed, i.e. information about the position of a fire if detected.

Said line fire detecting means 74 can preferably comprise heat-sensitive sensors, conveniently based on fibre-laser technology, i.e. comprising heat-sensitive fibre optic cables. Moreover, the line fire detecting means 74 are coupled to line communication means 75, which, in turn, are coupled to the electronic control unit 73 to which they send the data received from the. line fire detecting means 74. Conveniently, in order to communicate with the electronic control unit 73, the line communication means 75 can comprise both wireless and wired technology, and/or can be based on the transmission networks already installed along the railway lines. Moreover, the ventilation system 70 comprises position sensing means 76 Installed on board each train, configured to provide the position of the respective train, and coupled to the on-board communication means 72, which also send the data acquired by said position sensing means 76 to the electronic control unit 73.

Preferably, the position sensing means 76 can comprise one of the train operation signalling, control and automation devices already installed on the trains, for instance such as the Automatic Train Control (ATC) which always knows the position and speed of the train on which it is installed.

The electronic control unit 73 is in turn coupled, conveniently by means of a SCADA (Supervisory Control And Data Acquisition) device,

• to the air vents 77 of the air duct to control their opening and closing;

• to the ventilation means 78 to control these; and

• to any line aerating means 79 installed along the railway line to control these.

When the on-board fire detecting means 71 detect a fire on board the train on which they are installed they send an on-board fire detection signal to the on-board communication means 72.

The on-board communication means 72 also acquire the position of the train on which they are installed from the respective position sensing means 76 and, when a fire occurs, send the on-board fire detection signal and the position of the train on which the fire has broken out to the electronic contr/ol unit 73.

Moreover, when the line fire detecting means 74 detect a fire at the point along the railway line in which they are installed, they send a line fire detection signal to the line communication means 75 with information about the position on the railway line in which they are installed, i.e. information about the position of the fire. Thus, when a fire occurs on the line the line communication means 75 send the line fire detection signal to the electronic control unit 73 along with the respective position of the fire.

When a fire is detected on board a train and/or on the railway line, the electronic control unit 73:

• calculates, on the basis of the position of the train that is on fire and/or of the fire on the railway line, which and how many air vents 77 of the air duct to open in proximity to the train that is on fire and/or the fire, and thus opens these,- and

• calculates, on the basis of the position of the train that is on fire and/or of the fire on the railway line, which and how many ventilation means 78 to activate as extractor fans and thus activates them as extractor fans.

Moreover, when a fire is detected on board a train and/or on the railway line, the electronic control unit 73 preferably:

• calculates, on the basis of the position of the train that is on fire and/or of the fire on the railway line, which and how many ventilation means 78 to activate as blowing fans and which and how many air vents 77 of the air duct to open in correspondence with said ventilation means 78 activated as blowing fans, and thus activates said ventilation means 78 thus determined as blowing fans and opens the air vents 77 located in correspondence with said ventilation means 78 activated as blowing fans; and/or

• calculates, on the basis of the position of the train that is on fire and/or of the fire on the line, which and how many line aerating means 79 along the railway line to activate as blowing fans and subsequently activates them as blowing fans.

Lastly, the space between the air vents 77 of the air duct depends on the average length of the trains, the geometry of the tunnel in which the air duct is installed and the exhaust capacity required to eliminate the smoke .

Conveniently the air vents 77 can be spaced at between 10 and 40 metres apart to obtain satisfactory extraction, and the air vents 77 can be opened, for instance in the case of an underground train, at a rate of 7 to 10 every 10-50 metres.

In other words, the 10 to 12 air vents 77 in the middle of which there is a fire can, conveniently, be opened.

The devices for opening/closing the air vents 77, controlled by the electronic control unit 73, can conveniently consist of electrically actuated airlocks also comprising a limit switch device. Said electric actuation can conveniently be performed by means of a dedicated electric panel incorporating a programmable logic controller (PLC) that can interface the electronic control unit 73 via a SCADA device.

The advantages of the present invention are immediately apparent from the above description. For instance, it is Important to underline that, with the ventilation system according to the present invention, the tunnels are no longer filled with smoke and it is no longer necessary to identify preferential escape routes which involve all the limits described previously.

In particular, the passengers can escape in both directions, even if experiencing panic. This almost halves the time required to evacuate the train, as both directions of the emergency platform are used, doubling their handling capacity.

Moreover, the ventilation system according to the present invention is not only advantageous for extracting smoke in the event of a fire, but also under ordinary operating conditions of the railway network, conveniently of an underground railway, and in particular: • to guarantee proper ventilation in tunnels and stations in order to eliminate the heat generated by- fixed systems and the normal movement of the trains,- and

• to reduce the pressure wave caused by the movement of the trains, known as the "piston effect", which can adversely affect the performance of any platform edge doors, i.e. the barriers separating the railway track and the platform at the station frequently used to guarantee the safety of passengers by preventing them from accidentally falling onto the line, especially on driverless underground railways.

The platform edge doors are often subject to stress due to the overpressure caused by the trains moving.

Said overpressure is normally contrasted by implementing air balancing vents, consisting of expensive and technically challenging shafts installed in proximity to the stations, and consisting of light wells with a cross-section of approx. 10-20 square metres extending from the underground station to the outside.

The air duct of the system according to the present invention can thus act as a sort of air balancing vent, since the pressure wave can be absorbed by the air vents and piped to the outside, thus reducing the overpressure on the platform doors.

Therefore, the ventilation system according to the present invention avoids the need to implement air balancing vents or significantly reduces the size of these.

Moreover, as mentioned previously, the ventilation system according to the present invention no longer involves the need to implement air shafts, which are very expensive and technically challenging structures.

Lastly, it is clear that various modifications can be made to the present invention, all of which fall within the scope of the invention as defined in the appended claims.