The municipality of Leiden is working to improve the city’s accessibility, and particularly that of its Bio Science Park. To fully utilise the development potential of the Bio Science Park, the implementation of a new access road from the Plesmanlaan to the Bio Science Park is imperative, as is the improvement of the flow of traffic on the Plesmanlaan. In 2014, Karres en Brands won the competition for the design of access to the area. The goal of the design is to make the entire Plesmanlaan a single, coherent boulevard, a recognisable and appealing approach to the centre of Leiden from the A44. Through the consistent placement of trees, forming a green median, shoulders, and exposed lanes, clear and coherent contour is created. That is essential: the boulevard will surely form the frontage of the new development of the Bio Science Park, as well as a calling card for the city.


The proposed interventions are simple but effective. A rhythm of alternating rows of trees on the roadside will be placed along the Plesmanlaan and Haagse Schouwweg. The rows of trees thus slide past each other like a theatre set design; this pattern is applied over the entire length of the Plesmanlaan. To give the entire area a green atmosphere—and to avoid that the greenery only appears at its edges—a continuous median planted with grass and a double row of trees will be realised. The green median of the Plesmanlaan continues into a tunnel, by which the atmosphere and look of the boulevard is not limited to the ground level but forms a continuous line. This creates a broad underpass that keeps the view towards the adjacent trees as free as possible. The span of the bridge deck is free of columns, forming a spacious, bright, and high-quality underpass. In addition, the walls are placed at a slight angle so that the tunnel increases the view over the surroundings and admits a maximum amount of daylight.

Essential to the road design is that the lane markers, roadway, and lanes are designed in as clear and fluid manner as possible. This contributes to a calm and clear road layout, whereby a safe situation is created. This, in combination with intelligible signage, contributes to a logical orientation and the role of the zone as a fully fledged entry to the city Leiden.

Other designers involved: ipv delft, DTV Consultants
Project location: Bio Science Park, Plesmanlaan, Leiden, The Netherlands
Design year: 2013 – 2014
Year Built: 2014 – 2016


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