Putting Roads Underground - the Case for Tunnels, Fly-unders and Highway Decking in London

Putting Roads Underground - the Case for Tunnels, Fly-unders and Highway Decking in London

Nominated for The Planning for Sustainable Land Use and Transport Award


David Jowsey, Transport for London, Chris Porter, Transport for London


As part of London’s Roads Task Force TfL have explored the potential to relocate road space underground through integrated highway engineering and landuse planning to release space for walking/cycling,enable development and improve traffic movement


In 2013, the Mayor of London’s independent Roads Task Force (RTF), comprising a diverse group of road users, developers, local authorities and other statutory highway authorities, helped to create the strategic direction for London’s roads. This vision is designed to tackle congestion and improve quality of life in London, and has the following core objectives:
• To enable people and vehicles to move more effectively on London’s streets and roads;
• To transform the environment for cycling, walking and public transport; and
• To improve the public realm and provide better and safer places for all the activities that take place on the city’s streets, provide and enhanced quality of life and help to unlock development and deliver new homes.

A key recommendation of the RTF report, published in July 2013, was that the potential of major highway interventions such as tunnels and ‘fly-unders’ should be investigated to determine the role they could play in achieving the vision for London’s roads and streets across the strategic highway network. In particular, whether major interventions at key locations could ‘relocate or provide substitute capacity for motorised traffic to unlock surface space for ‘living’, more sustainable modes and development – enabling different use of space above and reducing impacts such as severance and noise, while maintaining network functioning’. This view built on experience from other cities around the world such as Paris, Oslo and Boston, which have undertaken these kinds of ambitious projects and have seen dramatic results.

Since the recommendations of the Roads Task Force were published, TfL has been carrying out a number of strategic studies to understand the opportunities for roofing over or tunnelling under existing infrastructure at particular locations. Three main types of infrastructure were considered:
- Tunnels to release land at the surface for either development, green space, improved public realm or better facilities for pedestrians, cyclists and public transport users but also relieve congestion and improve journey time reliability
- Fly-unders to relieve congestion and improve journey time reliability and releasing road space at the surface to be improved for pedestrians and cyclists plus improving public realm
- Decking of roads to provide public parks, reduce severance and the negative impacts of roads including noise and poor air quality and helping to bring forward development on neighbouring land especially where there is good existing or future public transport connectivity which can support high density development

From an initial list of approximately 70 locations, a shortlist of fifteen sites has been identified for feasibility studies. For each identified site these studies have investigated:
• Potential intervention types;
• Engineering feasibility;
• Transport impact for all users including those travelling by car, foot, cycle and public transport;
• Local and strategic environmental impacts including on visual amenity, noise and air quality;
• Level and quality of enabled development;
• Likely programme;
• Route to consent; and
• Cost of delivery.

As a result of these studies, five locations have been identified as having potential to provide a significant contribution to achieving the aims and objectives of the Roads Task Force. This was recognised by the Mayor of London in February 2015, and has resulted in further feasibility work being carried out at these locations.

The paper to the conference will expand upon the following:
- How to manage the different functions of urban roads and streets; particularly those related to ‘moving’ and ‘living’;
- Practicalities of sifting from a large number of potential intervention locations to identify those with the biggest possible benefits;
- How highway engineering, public transport provision and land-use planning can be integrated;
- Case studies and updates on those locations where we are progressing feasibility studies;
- Key opportunities and challenges identified from large scale highway infrastructure in an urban context; and
- Potential delivery and funding mechanisms to build large scale highway infrastructure.


Association for European Transport