Automation in a medium-sized city
BRESCIA: The Metrobus light metro will bring the benefits of automated operation to a city considered too small to justify a conventional metro
Francesco Di Maio, Senior Vice President, Transportation Systems, Ansaldo STS
The goal of the Metrobus project is to improve the quality of life in the city of Brescia. Providing urban travellers with the shortest possible transit times, integrating transport modes and improving interchanges will cut the need for private car use. It will reduce the overall cost to the city of all forms of transport, public and private, not least by reducing air pollution and noise.
The origins of Metrobus lie in a decision taken by the city council in 1986. The range of transport options available to the city were identified, then analysed from technical and economic viewpoints.
Comparisons of light rail, trolleybus, metro and other concepts showed that the most cost-effective long-term solution to Brescia's growing traffic problem would be a fully-automatic, driverless metro, which will provide the capacity to handle foreseeable traffic increases for the next 30 years.
An L-shaped initial line was conceived, linking densely populated areas and connecting the main traffic generators, including the university, hospitals, sports facilities, government buildings and city centre. The exact route was refined using mobility analysis to identify the optimal locations for the stations and maximise integration with the rest of the urban transport network. The result was the 13·1 km first phase line, serving 17 stations on a route from Buffalora to Prealpino.
Planning and authorisation procedures proved to be very drawn out, and tenders were not called until 2000. In April 2003 a turnkey contract worth a total of €575m was awarded to a consortium led by Ansaldo STS. The national government is meeting the majority of the cost, with significant funding from the city and regional authorities.
Ansaldo STS is responsible for the railway systems, including power supplies and control systems. The other members of the consortium are Astaldi, with responsibility for civil works, permanent way and mechanical and electrical installations, and rolling stock builder AnsaldoBreda.
Finmeccanica owns 100% of AnsaldoBreda, and 40% of Ansaldo STS, the remaining 60% being listed on the Milano stock exchange. Ansaldo STS and AnsaldoBreda have worked together on other projects, including the København metro (RG 1.03 p32), but they are independent companies and free to choose any partner to obtain the best technology to meet the needs of a particular scheme. In the case of Brescia, the technologies already in use in Denmark were seen as the most appropriate.
Construction began in January 2004, with works originally scheduled to take seven years. However the discovery of archaeological finds required more extensive investigation of the alignment than had been anticipated, and led to a redesign of some of the city centre stations. The first train is now expected to carry passengers in December 2012.
The adoptions of driverless technology will bring the transport benefits traditionally provided by classic underground systems in large cities, but on a scale appropriate to a medium-sized city like Brescia, which has a population of around 190 000.
The advantages of fully automated operation are:
- very frequent services. The design headway is 90 sec, allowing an intensive service during the morning and evening peaks;
- trains can run at closer intervals than under manual operation, making it easier to recover from delays;
- centralised control enables decisions to be made to ensure punctuality. We expect that at least 98% of departures will be on time;
- staff can assist passengers and take care of their security, instead of focusing on driving the trains;
- human error risks are lowered;
- capital and operational costs can be lower than for a traditional metro;
- operating flexibility, with additional trainsets put into (or taken out from) service at any time to meet any unexpected change in the demand for transport.
Metrobus operations will be monitored from a control room in the depot at Buffalora. Controllers will have access to all the information and systems needed to manage the metro, keep passengers informed and ensure safety.
Information provision is particularly important, and we will deploy an integrated telecoms system linking display screens, electronic signs and public address systems. This will be able to broadcast pre-programmed and real-time information outside the stations, on the platforms and inside the trains. Stations and trains will have help points where passengers can seek assistance, and users will also be able to obtain information at a Customer Service Centre or online.
The telecoms system is based on Tetra radio network technology with 30 fibre-fed repeaters linked to a radiating cable. There will be radio links between the control room and customer-facing staff, trains and maintenance vehicles.
A very comprehensive supervision system (Scada) of sensors and monitoring devices will enable the control room to check that circuit breakers, isolators, escalators, lifts, fire fighting equipment, ventilation and all the other equipment across the entire metro is functioning correctly. If something goes wrong, remote controls can be used to try to fix it.
The power distribution system will consist of four radial systems with double feeding from the 15 kV supply. Each station will be equipped with two 15/0·4 kV transformers feeding all the sub-systems installed at the station, and the most critical subsystems will be linked to an uninterruptible power supply to ensure their availability in the event of a failure of the 15 kV ring.
Seven of the 17 stations will be equipped with transformers and inverters to supply the third rail at 750 V DC. Regenerative breaking will be used, with power fed back into the third rail to reduce energy consumption.
City life undisturbed
Construction sites along the route have limited footprints, and will be opened in sequence and for short periods. Most activity will be underground, so the life of the city can continue undisturbed throughout the construction period.
The initial line requires 5·9 km of bored tunnel, with stations built from the bottom up. Around 20 to 22 m below ground level, these stations will have unobstructed space up to the sky to provide daylight all the way down to the platform.
Cut and cover tunnels 10 m deep will account for 3·8 km of the route. The stations on these sections will have flat roofs with skylights, allowing them to be located in streets or beneath squares and thus eliminating the need to expropriate surrounding buildings.
A further 3·4 km will be elevated on viaducts or embankments, and here the stations are being designed to emphasise easy access from street level.
All the underground stations will be fitted with platform screen doors, to be supplied by Knorr-Bremse under subcontract from the construction consortium. These will provide complete separation between the platforms and the tunnel area, preventing any access from platforms to the track and sparing the passengers from the wind created by train movements in the tunnels.
The stations will be unstaffed and have minimal facilities, as the high frequency of train services will mean that they are not waiting areas but merely transit points.
AnsaldoBreda is supplying its standard design of automatic metro car, which has been running successfully in København since 2002. The three-section articulated trainsets for Brescia will be 39 m long and 2 650 mm wide, assembled from extruded aluminium profiles and panels. Steel wheel on rail is being used, with three of the four bogies powered, giving a top speed of 80 km/h.
Each train will have 72 seats and two wheelchair spaces, with wide gangways giving space for a total of 300 passengers. A continuous view through the train will provide passengers with a sense of security, and CCTV will be fitted. Most trains will carry a steward to assist passengers, but this is not a requirement and trains can run unattended if the steward is assisting passengers on a station. The end cars will be fitted with emergency driving panels, permitting manual operation if needed.
The certification of the trains and the automatic train control is being simplified through the use of common designs with the Københaven metro. European rules now permit much of the basic approvals knowledge to be transferred. The basic safety of the vital automatic train control system has already been demonstrated, so only adaptations to suit the topology of the Brescia line will need certifying.
The initial line is just the first element in a wider network of Metrobus lines covering the city and outer-suburban traffic routes.
A 3·5 km branch is planned to run from Lamarmora station, through a densely populated area to terminate at the Fiera exhibition ground.
Taking Metrobus 14 km north along the Trompia Valley from Prealpino to Inzino is also seen as a natural extension, exploiting the geographical and economic continuity of the string of settlements along the route. The main Trompia Valley road is one of the most important routes into Brescia, carrying more than 20 000 incoming vehicles on an average working day. Extending Metrobus would benefit the whole area by cutting road use, accidents and pollution.
The planned extension would take the metro beyond the city boundaries, and agreements for the project have been reached between the city, Brescia province, the Lombardia region and local authorities along the valley. There will be 15 stations, and integration of Metrobus and bus services will lead to easier connections between the towns in the valley as well as into Brescia itself.
- CAPTION: The first phase of the Brescia metro includes 9·7 km of tunnel.
- CAPTION: The design of the underground stations allows daylight to reach the platforms.
- CAPTION: Everyday life is undisturbed by the construction activity beneath the city's streets and squares.
|Initial phase||Fiera extension||Trompia Valley|
|cut & cover||3·8||1·8||4·7|
|At grade km||1·7||-||-|
|Route length km||13·1||3·5||14·0|
|cut & cover||5||2||7|
|Trains||18 x three-car|
|Doors per side||6|
|Minimum headway||90 sec|