More than 120,000 vehicles travel along the A1 highway through Zurich's Schwamendingen district every day. For decades, the road divided the neighbourhood and brought constant traffic noise to residents living just metres away. In March 1999, local residents launched a popular initiative demanding an enclosure of the highway, and voters subsequently approved the financing in referendums.
After more than two decades, rough structural work concluded in 2024; following technical acceptance and final planting, the facility officially opened in May 2025. Instead of a simple noise barrier, a concrete enclosure was built, with the public Ueberlandpark directly on top. The YouTube channel Streetscapes presents the engineering and design behind the project in a video, using project visuals provided by Grün Stadt Zürich.
Building under live traffic and on a thin layer of soil
The highway does not run underground, but at street level through a large concrete enclosure. Alongside it, side streets provide access to the surrounding buildings and to the park on the roof. Beyond supporting the green space, the structure accommodates ventilation systems, drainage, electrical networks and a new building. Because the A1 could not be closed for construction, the work was carried out in stages while traffic continued flowing: first the western half was built, then traffic was shifted onto it so the eastern side could be constructed. Building the enclosure took 65,000 cubic metres of reinforced concrete and 232 prefabricated concrete beams up to 37 metres long.
On the concrete roof, every extra centimetre of soil adds weight to the structure below. To give the greenery enough soil to survive without exceeding the structural limits of the enclosure, the soil layer is between 31 and 81 centimetres deep. It was planted with drought-tolerant species that also increase biodiversity in the area. Trees were planted as well; because root space is limited, they will remain relatively small.
At 950 metres long and 30 metres wide, the park follows a linear layout. Along the continuous vegetation zones, it is divided into three gardens, three meadows, two playgrounds surfaced with wood and sand or rubber and sand, a square overlooking the highway and a central square. Modular benches designed specifically for the Ueberlandpark, some fitted with shade canopies for hot summer days, stand beside the trees and along two gravel path networks: a main route shared by pedestrians and cyclists, and narrower, quieter secondary paths. Drinking fountains provide fresh water 24 hours a day without buttons or sensors. At the centre lies a larger water feature and, as the only building in the park, a pavilion housing a café whose roof is completely covered with solar panels that power the building and generate an energy surplus.
Four levels of movement and new links across the neighbourhood
To prevent the enclosure's side walls from acting as a bare concrete barrier at street level, fast-growing climbing plants were planted at the base. Where vegetation was not practical, the planners chose exposed aggregate concrete whose rough texture and colour resemble natural stone. The same textured concrete finishes small structures in the park above that conceal emergency smoke extraction fans for the tunnel.
At both ends of the park, gently sloping ramps provide access for pedestrians and cyclists, while additional entrances in between connect the surrounding streets to the roof. Rain-protected bicycle parking is tucked beneath the ramps, and in the northern section a tube slide with no age limit leads back down to street level. At the heart of the project, four levels of movement meet: the park on top, the highway enclosure in the middle, the side streets beside it, and on the lowest tier the Milchbuck-Schwamendingen tram tunnel (lines 7 and 9, serving the underground stop Ueberlandpark, formerly Schörlistrasse) together with the underpasses beneath the highway. In the underpass crossing beneath the enclosure, motor traffic is separated from pedestrians and cyclists using different slopes: cyclists use a gentle gradient, while cars follow a steeper route that creates enough clearance for larger vehicles. Next to it, an elevator, stairs and a ramp lead up to the park. New housing developments are also emerging around the park; one building nearing completion connects directly to the park via two pedestrian bridges crossing over the side streets.
The Ueberlandpark is considered Switzerland's most expensive noise barrier. The investment was shared between the City of Zurich, the Canton of Zurich and the federal government, which contributed the largest share. For Streetscapes, the project points to an option for cities where removing an urban highway altogether, as Utrecht in the Netherlands did when it restored a former canal, is too difficult: reducing the impact of an existing highway while creating public space above it that brings the neighbourhood back together.