One of the focus themes of this issue is metro railway systems, and in this article we look at Sydney Metro – the first driverless metro railway in Australia. But to begin, what exactly is a metro railway?
Unlike other railways, metros only carry passengers and provide a more intense train service. They generally exist in cities and built-up areas, and can vary in size from a few kilometres to the metros in Tokyo, Beijing, or New York, for example, which are hundreds of route-kilometres in route length. Metros can move millions of people over relatively short distances, and operate intensely, often seven days a week, with minimal engineering time available for maintenance.
To achieve this, metro systems must be carefully designed and be very reliable and resilient. They need to be structured and integrated with other transport modes so that the densely populated areas they serve can operate efficiently.
Metro systems typically use Communications-Based Train Control (CBTC) as the signalling system. CBTC uses telecoms radio links between the train and trackside equipment, which allows a train’s position to be known more accurately than with traditional signalling systems. This can make metros more efficient with reduced headways.
A CBTC system is capable of providing Automatic Train Protection (ATP), as well as Automatic Train Operation (ATO) and Automatic Train Supervision (ATS). However, as metro systems are self-contained in a fixed area there is no requirement for interoperability. This means CBTC systems are ‘bespoke’ manufacturers’ systems with no interworking between suppliers’, unlike main line ETCS (European Train Control System). In many metros the headways are so short that the train service can only operate using ATO.
Traditional signalling systems detect trains in discrete sections of the track called ‘blocks’, each protected by signals to prevent a train entering an occupied block. In a moving block CBTC system the protected section for each train is a ‘block’ that moves with the train, with continuous communication of the train’s exact position provided via radio. The CBTC trains continuously calculate and communicate their status to the trackside equipment, including the exact position, speed, travel direction, and braking distance of the train.
Trains on metro systems generally move relatively slowly, compared to ‘main line’ trains, but they accelerate and brake more quickly. They tend to be of the same type and configuration, which means they have the similar acceleration, braking and top speed characteristics; and there are no slower moving freight trains to get in way!
There are generally fewer points, crossings and complicated junctions in a metro and, in general, there are no connections to neighbouring railways. Being self-contained and ‘closed systems’ means that it’s easier, in some respects, to implement innovative and creative engineering solutions than in more open main line railways systems.
Sounds easy, so what’s the problem? Well, a metro train can typically carry several hundred people in peak periods, with trains arriving seconds apart at busy interchange stations. Safely managing that many people, often in confined spaces, raises challenges which must be addressed, and this intensity of use means metros must be very reliable and resilient.
Sydney Metro
The initial Sydney alignment (Northwest and City & Southwest) will ultimately have 31 metro railway stations and be a 66km standalone metro railway system, with planned capacity of a metro train every two minutes in each direction under the Sydney city centre. These are:
- Western Sydney Airport Metro (Six stations and 23km in length).
- Sydney West Metro (Nine stations and 24km in length).
The first Sydney Metro network is made up of a number of sections. The Metro North West Line (formerly the planned 36km North West Rail Link) services started in May 2019 in the city’s North West between Rouse Hill and Chatswood, with a metro train running every four minutes in the peak. With 21 stations on 22 miles (36km) of twin tracks, and much of the line underground, it was signalled by Alstom using its Urbalis 400 CBTC system. This Grade of Automation (GOA) 4 system is fundamental for smooth efficient driverless operation. See Table 1 for an explanation of GOA.
GOA4 is not simply a train that drives itself. The functions normally provided by a human train operator or driver and a signaller are replaced by a digital system of interacting hardware and software systems. These must achieve an outcome at least as good as a human train operator/driver and signaller. So, there are many other things which need to be addressed, such as noting track defects, infrastructure failures, severe weather conditions, things on the track, and train evacuation in an emergency.
Sydney Metro City & Southwest
The Sydney Metro City & Southwest section includes a new 30km metro line extending metro rail from the end of the Metro North West Line at Chatswood, under Sydney Harbour, through new, very impressive, iconic stations, and southwest to Bankstown, with an ultimate capacity capability to run a metro train every two minutes each way through the centre of Sydney. This is known as the City Section and recently opened.
In addition to the new metro stations at Crows Nest, Victoria Cross, Barangaroo, Martin Place, Pitt Street (renamed Gadagel), Waterloo, and new underground metro platforms at Central Station, 11 existing stations between Sydenham and Bankstown were upgraded to impressive metro standards.
The second stage to extend the line to Bankstown on an existing ‘brown field’ railway is now underway, with completion in late 2025. The work required is so significant with, for example, new platform screen doors on curved platforms and upgrade from GOA1 to unattended train operation GOA4, that the line is currently non-operational. This is along a route of some 15km all of which is at-grade, so a GOA1 to GOA4 upgrade of this scale is probably unique and a world first.
With the route being an existing one, the curved platforms provide a challenge for the screen door design with, for example, mechanical gap fillers and obstacle detectors required to enable the provision of an inclusive environment for all train and station users. An inclusive environment is one that can be used by everyone, regardless of age, gender or disability.
The line runs parallel with the Australian Rail Track Corporation freight corridor for approximately 50% of its length before reverting back to two lines for the remaining 7km. The line also experiences a significant amount of trespass. This will require appropriate measures such as intrusion detection and fencing to ensure the GOA4 line and the UTO corridor is fully protected.
The requirements for the extension from Chatswood and the building of the Metro City & Southwest were multi-faceted. The metro will provide greater connectivity into the city from the northwest, which is an expanding growth area, to alleviate existing traffic congestion in the south, thus enabling enhanced services on the City Circle line and at the same time increase economic development opportunities along the southwest corridor.
The Sydney Metro City & Southwest project has differing challenges. The City section involved the introduction of ‘integrated station developments’ but the Southwest section requires the conversion of an operational railway, and to minimise the time between the cessation of the existing Sydney Trains operations and the introduction of new GOA4 operations – which is easier said than done.
The Bankstown line has been in operation for over 100 years and many of the stations are heritage listed, which severely constrains the amount of civil and structural changes that are allowed to take place. This resulted in eight of the 10 stations with curved platforms being retained. This constraint, along with the need to make the metro system fully Disability Discrimination Act (DDA) compliant, and the metro rolling stock being 150mm narrower than the old trains, has added to the complexity of the conversion in the station areas involving the platform screen doors.
All of this means that a significant amount of the existing infrastructure in the corridor must be retained and made to operate under metro operations whist at the same time to deliver the existing operational and customer service requirements. There was also a requirement from government that the Sydney Trains operations on the line continued for as long as possible, so it wasn’t easy to implement many of the changes required for metro working in advance of the final shutdown.
While new traction substations are being provided along the corridor, much of the existing overhead catenary line and equipment and all of the structures will be retained. By applying a process that demonstrates the assets meet reliability, availability, and maintainability targets, Sydney Metro has proven that these assets will comply with the key performance measures for metro operation and are fit for the purpose intended. This same process has also been applied for the track, cuttings, embankments, and retaining walls.
Pre-shut down works
The pre-shut down works involved testing and performance proving of systems, plus specialised product development, acceptance, and approvals together with early integration testing where possible. The majority of the platform rebuilds and station refurbishments were carried out. This included raising the platforms to ensure horizontal alignment for the new metro trains to manage the train to platform interface for future operations and ensure DDA compliance. Other works carried out included the facilitation of the future platform screen doors and mechanical gap fillers which could only be installed during the shutdown period.
Other works included systems such as Public Address (PA), visual customer information systems, CCTV and help points, plus the installation of Building Management Control Systems (BMCS) and fire systems. An exception was Bankstown which cannot be completed due to the need to physically separate Sydney Trains network from Sydney Metro at the station and install a new at grade concourse between the two operations.
A new 11kV High Voltage (HV) distribution system has been installed to provide the low voltage power requirements for all stations as well as the equipment rooms in the stations and along the corridor. Other corridor protection activities included the installation of anti-climb and anti-throw screens on bridges, plus the provision of a corridor intrusion detection system to be completed during the shutdown period.
During the Christmas and New Year period of 2019/2020, the existing lines from Bankstown were diverted to arrive at Platforms 3 and 4 at Sydenham Station, thus freeing the existing Sydney Trains Platforms 1 and 2 for future metro operations. A Common Services Route (CSR) was provided for the cable containment for high voltage (33kV and 11kV), signalling and telecoms cables. There were challenges with providing the CSR which required close liaison and agreement between Sydney Trains and Sydney Metro due to the route being 2.5 metres high, which impeded access to the live operational assets.
Between Sydenham and Campsie, access was only on the down side due to the ARTC freight line running along the same route and the need to provide a segregation fence between the two operators. This meant the cable route could only be constructed on the down side.
Sydney Metro required three new turnouts located at Bankstown, Campsie, and Sydenham, plus two existing Sydney Trains turnouts at Campsie to be renewed and retained. The new turnouts had to be clamped, locked, and detected by the Sydney Trains signalling system but not integrated into the Sydney Trains control.
Extensive static testing of the metro operational systems (signalling, communications, radio, and station systems) has been carried out as far as possible throughout the last two years.This required considerable coordinated cooperation between Sydney Trains and Sydney Metro as access was constrained to a three-to-five-hour window.
International delivery
With the line now closed, work is finally underway to fully convert the legacy railway line to unattended GOA4 metro operation, including the installation of the platform screen doors and mechanical gap fillers for the curved platforms, plus the corridor wide intrusion detection system consisting of fibre cable and CCTV cameras.
Sydney Metro has looked for the best expertise and systems from around the world to deliver its iconic GOA4 metro system. This includes engineers from the UK as well as international engineers and suppliers.
This once-in-a-century metro infrastructure investment programme will transform Sydney for generations to come, doubling rail capacity, linking new communities to metro rail services and supporting employment growth and housing supply. It’s a tricky programme involving greenfield new lines, iconic new stations, and converting legacy railway lines to GOA4 unattended operation, but it is a great example of how intense metro rail systems are essential for a modern city to function.
Many thanks to Steve Allday for his assistance with this article.
Image credit: James Tomlinson