One of the most effective ways of increasing the carrying capacity of a metro line is to install an automatic train control system. Barcelona Metro is currently piloting IRG’s TBS500 Driverless System on their Line 11, with a view to extending the technology to other lines on the metro network.
Train control systems can classified into different levels of automation depending on the degree of facilities that they provide. At a basic level there are automatic train
protection (ATP) systems supplemented with manual control.
Next, there are systems where automatic train operation (ATO) is implemented in each section of line between stations, but with an employee present in the operational cab in order to manually operate the train doors and to start the train. These are now considered to be semi-automatic systems (STO).
Systems where an on-board employee can leave the driving cab of the train in order to carry out other duties, such as dealing directly with passengers, are known as driverless (DTO) or unattended operation (UTO). These latest generation systems are fully automated
Line 11 of the Barcelona Metro is 2.15km long and links the districts of Trinitat Nova, in the outer zone of Barcelona, with the district of Can Cuiàs in Montcada i Reixac. It has a total of five stations - Can Cuiàs, Ciutat Meridiana, Torre del Baró, Casa de l'Aigua and Trinitat Nova. It is at this last station that it connects with Line 4 of the Metro Network.
Historically, this area of North eastern Barcelona had been difficult to access using surface public transport because of its hilly nature. The line consists of a single track, except in the crossover station of Torre Baró – Vallbona. The platforms are 40 m long.
The TBS500 Driverless System, supplied by IRG’s Dimetronic Signals, is an integrated automatic train control (ATC) system for underground railways based on the ‘target distance’ principle. It includes an automatic train protection (ATP) system and an automatic train operating (ATO) system. The equipment on board detects free blocks of track in front of the train. This information is supplemented with the known length of the blocks, and data relating to the track profile/gradients. A train can thus approach a block occupied by the preceding train without reducing its speed, up to a distance permitting it to brake before reaching the block occupied by the previous train.
The system opens and closes the train doors and also the platform doors.
The train is started automatically, runs on sections of line between stations and reverses at termini.
The employee on board the train is responsible for initialising the system, and may leave the cab during normal operation of the system in order to carry out duties involving passenger supervision or assistance. When the system was developed, consideration was given to several degraded modes in which the employee on board drives the train.
Line 11 signalling is controlled by Westrace electronic interlocks installed at the Trinitat Nova and Torre Baro stations. These Westrace interlocks have a dual hot stand-by configuration with a high degree of availability. The track is divided into blocks by means of type FS2550 jointless track circuits, which are used not only for detecting the presence of a train but also for the continuous transmission of coded signals (ATP codes) to the trains.
Passive balises , distributed along the track, are activated when the trains pass. They provide data permitting the trains to be located with maximum accuracy, an aspect which is absolutely essential in a ‘target distance’ system.
ATO track equipment is installed in each of the stations on the line. It is used for transmitting automatic operation information to the ATO equipment on board, including control data originating from the centralised control terminal.
In order to increase the high degree of availability essential for an automatic system, the ATP system on board has three independent channels in a voting "two out of three" redundant configuration. The ATP unit consists of three processing channels operating in parallel which check between themselves and enable the outputs as if a single equipment were involved. If any one of the three channels fails, the system detects this condition but continues with no reduction in performance.
In addition, the system on board also has duplicate ATO equipment and each ATO unit consists of one processing channel. In the event of an incident, the system switches (automatically) to the second channel.
On enclosed metro systems, the primary interface of the train with the public is as it enters a station. Driverless systems require station platforms to be modified and fitted with devices to prevent persons or objects falling onto the track. These include platform gates or screen doors (PSD). Opening and closing operations and synchronisation with the doors of a train must be controlled by the system itself.
Two-way train/track communications equipment is installed at all of the stations. This equipment ensures increased stopping accuracy at the platforms to ensure that the trains are correctly positioned. Train doors must be face to face with the platform gates. Once at a stand, the system ensures that the operation of the train and platform doors are synchronised.
The PSD equipment communicates with the ATO equipment on board the trains by way of inductive transmitting and receiving loops installed at the stations. Communication between track and train is achieved by making these inductive loops (one for transmission and the other for reception) coincide with the corresponding train antennas. The transmitting loops are longer than the receiving loops and, unlike the latter, have multiple crossovers for detecting the position of the trains and recalibrating distances. The receiving loops are short and do not have crossovers.
The receiving loops are arranged on the track so that the transmitting antenna of the train is positioned right in the centre of a receiving loop when the train pulls up correctly in its stopping position in a station.
As soon as a train stops correctly at the platform with its receiving and transmitting antennas coincident with the inductive transmitting and receiving loops provided for two-way train–track communication, contact is established between the train and the station PSD equipment.
The train ATO equipment transmits a command for the train doors to open and a command to the station PSD equipment for the platform gates to open. The station PSD equipment transmits a command to the relevant platform gate opening system, for the gates to be opened.
The platform gate system transmits the status of the platform gates (open or closed) to the Westrace interlock used to control the station. When the data received indicates that the gates are open, the interlock selects a suitable ATP code in the station track circuit in order to prevent the train from moving.
When the waiting time at the platform ends, the Westrace interlock receives the corresponding permission to depart and then selects the appropriate ATP code which indicates "track clear – permission to depart, but platform gates open". The interlock continues to prevent the train from moving, but lets the train ATO equipment know that it may, from that moment, give a command for the train doors and platform gates to be closed.
The train ATO equipment orders the train doors and platform gates to be closed simultaneously by way of the station PSD equipment.
The station PSD equipment transmits a command to the relevant gate system for the platform gates to be closed, provided that it receives the "track clear" indication transmitted by the interlock.
As soon as the platform gates are closed, the gate system transmits this information to the Westrace interlock and the station PSD equipment. The latter transmits this information, via the inductive transmitting loop, to the train ATO equipment which is finally able to close the train doors.
At the same time, the Westrace interlock receives an indication that the platform gates are closed. It then changes the ATP code of the stopping track circuit, thus permitting the train to start automatically from this moment once it has been verified that both the train doors and the platform gates are closed.
The modular design and considerable versatility of the Dimetronic TBS500 system is perfectly suited to the requirements of the Barcelona Metro for the operation of Line 11. This has enabled it to gradually implement various functions and degrees of automation in stages, moving from an ATP/ATO system with speed code functionality to a powerful ATP/ATO ‘target distance’ system that also permits driverless operation without interrupting the service on the line.
It was planned that the Line 11 system would be implemented in three stages. In the first stage, which had very strict completion dates and which was put into service in October 2003, the line was equipped with an ATP/ATO system with speed code functionality (the Dimetronic TBS100 system). At that time, the line was not equipped with platform gates. The employee on board the train was positioned in the driving cab and carried out tasks such as closing the train doors in a station and starting a train on its journey to the next station.
Reversing operations required at the terminal stations (Trinitat Nova and Can Cuiàs) were also carried out manually. The configuration of the Can Cuiàs terminus does not permit sufficient safe clearance for trains to enter in ATP speed code mode, and they therefore entered that station in manual mode.
The current second stage, in which the functionality was changed to a ‘target distance’ system, was put into service during July of the following year. This provides greater capabilities and permits trains to enter Can Cuiàs under the protection of the ATP system. In this second stage, as in the first, the employee is positioned in the driving cab, and is responsible for opening and closing the doors and starting the train.
Work has now begun on the installation of platform gates on the stations of the line. It is envisaged that, as the platform gates are installed and tested, they will be opened and closed automatically, and synchronised with the train doors by the system.
It is anticipated that the TBS500 driverless system will go into service at the end of 2007, as soon as the installation work on all the platform gate systems has been completed. The employee on board will be positioned in the passenger area, and the platform gates and train doors will be opened and closed, and the train started automatically.
Line 11 of the Barcelona Metro will become Spain’s premier reference site for metro line automation.
Notes to Editor:
A guide to the acronyms:
ATC - Automatic Train Control
ATP - Automatic Train Protection
ATO - Automatic Train Operation
STO – Semi-automatic Train Operation
DTO – Driverless Train Operation
UTO – Un attended Train Operation
PSD – Platform Screen Doors
