Report: Redefining bridges and tunnels

Redefining bridges and tunnels for the next generation of our cities

Urbanisation has made European cities denser and available urban spaces scarcer. This means that we must start thinking differently about our infrastructure. The area under a bridge might be a dark, unwelcoming space that people take detours to avoid. Or it might be a venue for community activities and outdoor meetings. To explore the full potential of our bridges and tunnels, we need to think in new ways. In this report, “Redefining bridges and tunnels for the next generation of our cities”, Sweco analyses cases where bridge and tunnel areas have been used successfully and proposes methods for reinventing infrastructure in European cities. You can download the full report by via a link at the bottom this page.

In 1980, the last train ran on the High Line railway in New York, pulling three carloads of frozen turkeys. After the railroad was vacated, a group of local residents and activists started advocating its conversion into a public landscape. In 2006, more than 25 years after the railway was decommissioned, work began on transforming the old viaducts into a green elevated park. Today, the park is considered one of New York’s most spectacular sights, visited by 5 million people annually.

The High Line is one example of how an existing, vacant structure can be redesigned to transform a community and create value for citizens. The same results can be achieved in many cities, simply by thinking differently about bridges and tunnels. “Redefining bridges and tunnels for the next generation of our cities” explores the potential of new and existing tunnels and bridges to reduce barriers and provide urban spaces and functions that improve quality of life in Europe.

Possibilities presented by bridges and tunnels

Historically, the main function of bridges and tunnels has been to connect different geographical areas, but they will also serve as important social connectors as our cities expand. As European cities densify, available urban spaces become scarcer, while the need for these spaces increases. As cities change, we need a new understanding of how to make optimal use of city areas. Tunnels and bridges should no longer only be structures that facilitate transport – their areas should offer an added value to the city and its citizens.

As cities develop, some existing structures become less useful or relevant for their time. Some even create barriers that generate empty and dark wastelands in surrounding areas. There are many cases where such structures have been reprogrammed to use vacant spaces in creative ways and add value for citizens. One example is the “Via Verde” initiative in Mexico City, a project to transform more than 1,000 flyover and elevated road columns into vertical gardens. The objective is to reduce pollution, improve cityscape aesthetics and lower drivers’ stress levels. Another example demonstrating how an existing structure can be reprogrammed is the Ammerud Underpass in Oslo. A dark concrete tunnel was transformed into an inviting space for exercise and leisure activities, with a climbing wall, fitness facilities, lighting and colourful walls.

Often, the construction of new bridges and tunnels can improve mobility in a city. The world has committed to the Paris climate agreement to reduce city pollution. Constructing new structures that add value to their surroundings can promote sustainable means of transport and improve the pedestrian and cyclist experience. One example of this is the “Bicycle Snake” in Copenhagen – a 230-metre-long winding sky bridge with bicycle and pedestrian lanes. The bridge creates a shortcut between two parts of the city, providing a unique, enjoyable cycling experience on an elevated bike path that runs across water and between buildings.

Bicycle Snake. Photo by Ingri Kvamstad

New bridges and tunnels can sometimes revitalise entire neighbourhoods. Areas with underdeveloped connections to their surroundings may suffer from vacancies and attract unwanted behaviour. Bridges can reduce the barriers between districts, and directing the flow of people through an area creates a safe and secure environment. One such example is the Luchtsingel bridge in Rotterdam, a temporary structure financed by over 2,000 crowdfunders. It runs through the Hofplein area, previously a neglected and detached part of Rotterdam dominated by vacant high-rise buildings. Connecting the Central Station, Rotterdam North and the Binnenrotte area, the bridge is a catalyst for economic growth.

Luchtsingel. Photo by Guro Ranum

Conclusions and recommendations

Bridges and tunnels are essential to urban mobility, accessibility and connectivity. As European cities densify, available urban spaces become scarcer while the need for these spaces increases. We therefore need to make the best possible use of all city areas and take all aspects of sustainability into consideration.

There is one recurring factor that we believe is essential to the success of transformative and greenfield projects: namely, a strong focus on the citizens’ perspective and involving people in a constructive dialogue on how the spaces can be used. Well-planned public spaces attract visitors, which in turn attracts others. By implementing the citizens’ perspective in all project phases, we can build bridges and tunnels as efficient mobility systems that break down barriers while also providing urban spaces and functions that improve quality of life.

Based on the case studies presented in this report and on our experience, we recommend a 5-step working method to utilise areas and spaces near bridges and tunnels.

Mapping areas under elevated structures is the first step of the process. Here, European cities can learn from the New York mapping initiative “Under the elevated”. The initiative identifies the space that is available underneath elevated structures and bridges. This concept can also be implemented in a European context and serve as a good first step in improving bridges and tunnels in European cities.
Our cities are constantly growing and developing, which changes the use of built structures. With mapping, analysis, dialogue and a little bit of imagination, existing spaces and structures can be used to enhance quality of life for citizens and create value in European cities.

Case – london underline

How can decommissioned tunnels under cities be transformed to add value for citizens? Beneath London’s busy streets run dozens of kilometres of vacant tube tunnels. In the London Underline conceptual project, architecture firm Gensler envisions developing these tunnels into a massive network of bicycle and pedestrian highways.

By utilising the abandoned tunnels, Gensler hopes to create a carbon-neutral community that is also self-sustaining. They suggest using technology such as Pavagen’s walkway tiles – engineered surfaces that convert energy from footsteps and bicycles into electrical power. Given enough area and traffic, these tiles will be sufficient to keep the tunnels completely self-sustained.

There are also plans to connect multiple tunnels across London, giving the city a vast travelling network that completely avoids the traffic, pollution and noisy world above.

London Underline, concept by architecture firm Gensler