For the grade-separated section of the Wippolderlaan (N211) near Delft, CI-Engineers worked on the structural engineering of a large concrete road deck. The deck forms the crossing between the sunken N211 and the N222 and Wateringveldseweg above.
Commissioned by Mobilis, CI-Engineers carried out the structural calculations for the road deck. It consists of a prestressed concrete slab with an area of approximately 1,000 m² and a weight of more than 3,000 tonnes.
One of the key challenges of the project was the limited construction time available. The N222 and Wateringveldseweg could only be closed for the works during two extended weekends. During the first weekend, among other activities, the tunnel wall was constructed on which the road deck would eventually rest.
On 5 September 2026, the complete concrete deck was transported into its final position. Self-Propelled Modular Transporters (SPMTs) were used for this operation. Due to the deck’s considerable weight and dimensions, several linked transport modules were required. Just two days later, on 7 September, traffic was already able to use the new deck.
Following the installation of the deck, excavation of the approach sections will continue and the soil beneath the road deck will also be removed. The tunnel floor will then be poured, followed by the remaining structural and finishing works for the grade-separated section.
This distinctive construction method made it possible to place a large and heavy structure in its final position within a very short period of time, while keeping disruption to traffic on the roads above to a minimum.
Client: Province of South Hollland
Contractor: Mobilis