Widening of the Kniplaan Viaduct Boosts Wildlife

The “ executive board ” group of the mayor and aldermen of Voorschoten wishes to contribute to an additional widening project at the Kniplaan viaduct over the A4, planned for 2026. This widening—a green vegetation strip—is intended to serve as an ecological corridor for small mammals and insects. This will provide them with better opportunities in the meadowlands of the Green Heart all the way to Horsten and Duinen in Wassenaar.

The existing Kniplaan Viaduct is already being widened because it no longer meets the requirements. Currently, that viaduct is used by local residents and recreational traffic. This green widening would therefore be an addition to that. It is not scheduled until 2026, but Rijkswaterstaat wants to know now what level of support there is for it in the region.
The ecological corridor would be 3 metre s wide. This is feasible from a planning, legal, and technical standpoint. Rijkswaterstaat and the regional partners of the Duin Horst en Weide landscape area have assessed this strip as the most realistic option for the widening of the A4 on the stretch between, roughly speaking, Leiden and Leidschendam-Voorburg. This will promote biodiversity.