London IS experiencing sustained growth. The population is projected to rise from 7.6 million in 2007 to around 10 million by 2030. The number of jobs in the city is projected to rise by approaching 20 per cent in the same period. To retain its world class status the city will depend heavily on the future maintenance and further development of its infrastructure systems including the transport network of which London Underground (LU, the ‘Tube’) is a key component.
Growth in demand
The London Underground is the busiest it has ever been. In recent years annual passenger journey numbers have risen steadily reaching over 1.2bn in the 2012/2013 year. On a typical week day over 4M individual journeys are made.
On Tuesday 7 August 2012 during the London Olympic Games a record peak of 4.57 million passengers used the Tube. Looking ahead current projections suggest annual journeys will reach 1.5bn by 2020.
The reasons for this growth include both the growth in the city and the steadily improving capacity and reliability of the public transport system. At the same time car ownership in London is in slow but consistent decline.
Underground civil engineering assets have a long life cycle. Significant parts of current network have now been in service for well over a century. Looking forward the challenge is now to enhance the infrastructure so that it can continue to cope with this projected demand generations into the future.
LU’s vision for the future
LU’s corporate vision is to meet these changing needs by providing "a world-class Tube for a world-class city".
In recent years the company strategy to achieve this has developed to include a formal recognition that the best use of technology is one of the essential elements underlying this. In other words there is recognition that we need to be open to new methods and materials for future work on the system. This is both an opportunity and a challenge for the underground construction community.
Of course the city cannot stop while infrastructure works go on. In practice the biggest challenge for many major works on the railway is to develop the engineering in such a way that new works do not disrupt day to day passenger services unless absolutely essential.
Infrastructure programmes
LU has committed to a programme of line and station upgrades. The line upgrades deliver new signalling systems and in many cases also new trains, to increase capacity by pushing more trains through the existing infrastructure.
The recently completed signal upgrades on the Jubilee and Victoria lines have successfully increased capacity. However these alone will not satisfy demand. The Northern line signalling system is being replaced and automatic train control introduced. The sub-surface lines are being upgraded with new trains and new automatic signalling. Once these programmes are delivered by 2018, the upgrades of the remaining deep Tube lines, already in feasibility and development stages, will then commence, delivering a new generation of trains and new signalling with automatic train control.
To support the train capacity improvements there is a parallel programme of station improvements. Major projects are currently underway at Tottenham Court Road, Bond Street and Victoria stations. These all include major tunnelling and civil engineering works. The next tranche of projects has started with the recent award of contracts for the Vauxhall Station upgrade and the Bank Station capacity upgrade. The Bank Station capacity upgrade is a significant project that will construct new southbound running and station tunnels on the Northern Line together with step-free access to the Northern Line and new links between the Northern and Central lines.
LU is already working on plans for the next stations to be upgraded. These include Holborn, Camden Town and Elephant & Castle where feasibility plans are being drawn up. This programme will require significant underground construction.
The redevelopment of the Vauxhall, Nine Elms and Battersea areas is being supported by the proposed extension of the Northern line from Kennington to Battersea. This would be the first new extension to the Underground since the extension of the Piccadilly line to Heathrow Terminal 5. The Northern Line Extension scheme consists of twin running tunnels from junctions on the Kennington Loop via a new station box at Nine Elms to a new station box at Battersea. Overrun tunnels will be directed towards Clapham Junction.
Although the major projects grab the headlines there is significant investment in day to day maintenance. The Track Partnership, a partnership of London Underground and Balfour Beatty is halfway through a track renewal programme. Traditionally civil engineering maintenance has been carried out at regular predefined intervals. This is being challenged particularly in drainage where a risk-based repair and maintenance regime using hydraulic design rather than replacing like for like is being implemented at the same time as the track renewel.
There is growing support for a plan to extend the Bakerloo further out into South London although no confirmed plan to proceed yet exists. The alignment would require some tunnelling to connect the existing tunnels with one of the suburban rail lines.
Beyond the current plans it is clear that more upgrades will be required to match the rising demand.
Technology
LU has committed to implementing Building Information Modelling (BIM) level 2 into future projects. BIM has the potential to deliver the following benefits:
A. Reduction of whole life cost, risk and carbon;
B. Reduction of construction waste and rework;
C. Design coordination across multiple disciplines;
D. Timely delivery of buildings and infrastructure projects; and
E. Increased confidence and efficiency in decisions making.
BIM is not restricted to buildings and structures, currently rolling stock are the most advanced with regard to BIM, as the new stock types have been designed using Level 2 BIM processes and technology. The laser scanning (LiDAR) is being routinely carried out to generate the base 3D models necessary for BIM.
The challenge for the next decade is to harness the advances in information technology to create smart infrastructure thereby reducing costs and more efficiently using the limited manpower available. In other words rather than continuing the current fixed interval manual inspections we should start to implement rail mounted automated laser scanning or digital imaging to support less frequent physical inspections. Although these technologies have been around for a decade or so they are getting more precise and improvement in post-processing is resulting in quicker review cycles. We are routinely scanning escalator shafts when the escalators are removed for maintenance.
These scans are used to build precise models of our structures that are incorporated into the BIM model for the station. These scans are unlikely be repeated for several decades and therefore provide a valuable record.
Improvements in wireless technology are beginning to impact on monitoring for infrastructure protection. In the last year we have deployed several wireless mesh networks where tiltmeters have been used to monitor deformation of the tunnel lining. We have also developed and deployed Smartplank and Smartstep. The former is a simple wireless device to measure the strain in timber planks and thereby investigate the load development in timber headings. The device can work autonomously or in a mesh with other monitoring devices. The Smartstep is an instrumented escalator step that is interrogated wirelessly at intervals to monitor the impact of construction works on the escalator. The development of both these devices recognises that most of the new infrastructure that we build in the future will be very close to our existing operational infrastructure.
Over the last 20 years we have seen increasing use of mechanised sprayed concrete technology and this has had a positive affect on the health of operatives by reducing the amount of manual handling and working at height. However because we must work around our existing infrastructure there is inevitably hand work, ring building and the installation of heavy beams.
Our challenge must be to develop a better understanding of the composite behaviour of concrete and steel to reduce the member sizes and thereby making best use of our existing skills to avoid hazards to health as well as safety.
Maintaining a team of high quality trained staff is a key element of our strategy. Our current projects rely on SCL to a greater or lesser extent and we have struggled to ensure that there are sufficient trained operatives.
This skill shortage was identified by Crossrail and led to the founding of the Tunnelling and Underground Construction Academy (TUCA) at Ilford.
The pace of technology change is rapid compared with the life cycle of railway assets. Looking back two or three decades tunnelling in London was very different to today. Hand excavation was much more readily accepted. Mechanised tunnelling usually meant an open face shield in good clay. Sprayed concrete was only just arriving in the city 20 years ago. A range of safety, health and environmental issues were yet to be considered.
If we look forward more than a few years it is hard to envisage what specific new technologies may influence the railway. However, it is possible to anticipate some of the issues that will be the likely future challenges.
Energy and sustainability
It seems inevitable that sustainability and energy consumption must become even higher priorities for future engineers. Underground railways are heavy users of electrical energy, which was historically relatively readily available and low cost in London (at least in comparison with some other world cities). In the future, energy cost for operating may well rise and there will be increasing debate over what energy sources are appropriate.
We will also become more conscious of embedded energy in our construction and minimising this may become a more significant driver for our new build works. At present London tunnel structures tend to be very robust and to feature large quantities of sprayed or cast in-situ concrete primary support that is disregarded in the long term. This means that there is potential to reduce consumption through efficient design with our current materials but also a challenge to designers to realise the benefits without incurring unacceptable risks.
It is also possible that new structural materials may be found to replace some of the current concrete and steel. We already see limited use of some polymers in LU structures. These include fibres for fire protection in concrete and carbon fibre composites for structural repairs. As an industry we need to be open to future use of more sophisticated but structurally efficient composite materials, with cement/polymer composites likely to be amongst the leaders.
Climate
Climate change is now widely accepted as a significant issue affecting future planning.
On the Underground cooling to maintain comfortable conditions is already a significant issue. LU is currently introducing new air-conditioned trains to the "Sub-surface lines." The deep lines in the LU system have smaller tunnels and smaller trains, which present greater technical challenges for heat management. LU has invested in systems including improved tunnel ventilation and ground water cooling systems but at present does not have a complete air conditioning solution suitable for trains that spend most of their time underground. As more people use the system the demand for this is likely to increase.
Another aspect of climate change is the potential for more frequent or more severe extreme weather events. In 2012 Hurricane Sandy had a severe impact on the infrastructure of New York and highlighted the potential vulnerability of underground structures. London has protective measures including the Thames Barrier but even these systems have a finite design life and future provision must be considered.
User demand
Increasing demand not only means more intensive services during the traditional peak periods but also greater use of the LU system at other times. The peaks have become longer time periods and there are now also peak demand periods at weekends. There is also an appetite for services running later into the night as was piloted during the London Olympics.
A practical consequence of this is that there will inevitably be pressure to minimise the time available to access the underground sections of the railway for routine maintenance at night and other closures of the railway for maintenance purposes. As a result there will be pressure to identify any technologies that reduce the need for man access for routine purposes such as inspection. Perhaps we need to consider more fundamental challenges. For example the possibility of simplifying the assets. The basic elements of the railway date back to the century before last. In the future perhaps it may no longer be appropriate to use a system of steel wheels on steel rails with lineside signalling equipment.
If future designs could reduce the fixed assets to a tunnel containing a low wear guideway with perhaps a simple communications spine all the other complex systems could be within the train. As the train returns to depot every day maintenance of train mounted systems can be much less disruptive than sending personnel into the tunnels.
Industry contribution
The challenges in efficiently maintaining and developing an old and busy railway network mean that there is always a need to apply the best available skills and technologies. When the use of the network is intensifying over time it becomes even more important. LU is keen to ensure that these opportunities are not missed.
Historically railways such as LU tended to rely on relatively prescriptive standards to ensure satisfactory performance from works. While beneficial in some respects this approach did not encourage the supply chain to propose better value solutions. More recently the greater use of performance specifications has allowed greater flexibility but there is still scope to improve practice.
In common with other major clients LU has recognised the potential benefits from early contractor engagement while planning works. Recently the company has piloted its own model of pre-tender industry consultation for the proposed Bank Station Capacity Upgrade with positive results.
Outside the world of large scale procurement LU has also provided other tools to aid suppliers in bringing new practice to the railway. Notable amongst these are an on-line approved products system (www.lu-apr.co.uk), which allows third parties to propose new materials and systems for use on the railway. This provides a relatively simple route for suppliers with innovative products to get them tested and, if they are successful, made readily available for future use.
Additionally Transport for London (LU’s parent organisation) has established an online "Innovation Portal" (www.tfl. gov.uk/tfl/innovationportal). The portal provides an accessible route that allows anyone to contribute suggestions or highlight new opportunities that might benefit the railway.
Collectively these mechanisms should provide real opportunity for those with good ideas to contribute to improving the transport system in London.
Conclusion
Since the start of London’s Underground 150 years ago, the system has evolved to satisfy increasing passenger demand. With demand at record levels and still growing the challenge facing LU is keeping the city moving while upgrading and expanding the network.
To meet this challenge and deliver the promised efficiencies and lower operating costs we must investigate new materials and technologies but we must also make more efficient use of current design technology. This will free up further capital to extend and improve the network in future
