A unique – stacked – tunnel in Hilversum

Hilversum, internationally renowned as the home of TV and radio stations in the Netherlands, isn’t exactly celebrated for its cycling infrastructure, locally. However, it now boasts something truly exceptional: the Hilversum Alexiatunnel, the nation’s first and only double-layered railway underpass, featuring a tunnel tube for motor traffic and a separate shorter tube for cycling and walking above it.

The south entrance of the cycling part of the Hilversum Alexiatunnel on top of the car tunnel. The green in the foreground is also located right on top of the tunnel for motor traffic.

Construction of the Alexiatunnel started in March 2020 and it was completed by August 2022. This underpass formed a crucial part of a larger project establishing a high-speed public transport corridor through Hilversum, partly paralleling the railway line. The tunnel’s uniqueness lies in its two layers: an upper layer designated for cyclists and pedestrians, and a lower layer for motor vehicles. This stacked tunnel design was chosen for its cost-effectiveness, allowing for the preservation of existing homes and buildings despite construction taking place at very close proximity.

The before situation as documented by Google Earth: a simple level railway crossing in an ordinary street.

The after situation: the 249 metre long car tunnel (with a black asphalt surface) and the 50 metre long cycling tunnel on top of it (with the red asphalt surface). Parallel to the railway you can also see the two new lanes of the rapid bus only route. Picture Google Earth.

Spanning 400 meters in length (including access ramps) and a width of only 10 metres, the tunnel descends to a depth of 12 metres at its lowest point, which is formed by a rainwater reservoir. The cycling portion is covered for 50 metres, while the section for cars extends 249 metres. This careful dimensioning (one metre below the threshold) avoided stricter tunnel regulations, simplifying operations.

The before situation in August 2018 (Picture Google StreetView).

The after situation at the exact same location in 2024. The buildings to the left were also there in the before situation, but the trees hid them.

Employing sustainable construction practices, such as utilising recycled materials and electric machinery, the project prioritised environmental responsibility. Excavated sand found new purpose in constructing a viaduct for a new bus route within the larger project scope.

The cycling tunnel’s walls feature aluminium plates adorned with 1.75 million perforations, depicting images of the sun and leaves, while LED strips illuminate the car tunnel, with functional lighting adapting to natural light levels for safety. A rainwater reservoir beneath the tunnel efficiently manages water, preventing flooding during heavy rainfall.

The north entrance of the cycling tunnel and a cross section of both tunnels and the rain water reservoir beneath those tunnels. The cycling tunnel is 5.5 metres wide. There is a side walk of 1.5 metres wide and the part for cycling is officially 3.5 metres wide. The 50 centimetres you are then left with were supposed to be a strip on the right (in this picture). Because a cycleway should be at least 50 centimetres away from any vertical objects (such as the wall). However, the road manager decided not to create that strip, in stead the right hand lane is 50 centimetres wider than the left hand lane. The bollard at the entrance is a bit weird considering that 50 cm rule.

The north entrance of the vehicular tunnel. The sign informs drivers how they should create space for emergency vehicles. If such a vehicle would want to use the tunnel there would be enough space when all drivers move their vehicles to the right as much as possible.

The tunnel’s completion significantly alleviates traffic congestion along a major artery in Hilversum, accommodating approximately 20,000 motor vehicles daily. It eliminates the former bottleneck caused by a level railroad crossing and provides a grade-separated crossing with the new high-speed public transport route, enhancing overall transportation efficiency.

Art in the cycling tunnel. Different sized holes in aluminium wall plates forming a pattern depicting the sun and leaves. This work of art was designed by artist Louise Hessel.

It is clear that some people struggle with the inclines. Hilversum claims the grades meet design recommendations, but with 5.32% and 4.77% respectively they are on the high end. The north incline for the car tunnel is even steeper at 6%. That would be unacceptable for a cycling tunnel.

Designed to deter graffiti with perforated steel panels, the tunnel exudes a welcoming ambiance through warm lighting. Furthermore, the project’s broader scope include developing a nature bridge at Anna’s Hoeve, east of Hilversum, and implementing tree replacement efforts to mitigate the environmental impact. On August 6, 2022, the tunnel was officially opened, celebrated with festivities marking the unveiling of both vehicular and pedestrian/cycling sections. Recognised for its innovative design, sustainable construction practices, and contributions to transportation infrastructure and safety, the project received a local architecture award in 2023.

My video report about the unique stacked tunnel in Hilversum.

A video with rides through the tunnel. First north to south and then south to north.