The Gaasperdammertunnel must be able to act autonomously after completion

THE CHALLENGE | The longest land tunnel in the Netherlands: that is the A9 Gaasperdammertunnel. Because this traffic link must also be able to act autonomously after completion, safety is an extra high priority.

Ballast Nedam is working on this project together with contract partners Fluor, Heijmans and 3i Infrastructure under the name IXAS. Commissioned by Rijkswaterstaat, IXAS designs, builds, finances and maintains the tunnel. Within IXAS, the design team of the technical tunnel installations teaches the tunnel the correct behavior, after which the test team determines that this behavior actually works. They do this by devising specific tests that demonstrate this up to a certain level of certainty. In addition, the test team ensures that stakeholders and other interested parties can also observe this.
All systems must provide the correct behavior in all cases.
Michel van Corven Test manager Ballast Nedam
The law requires all tunnels longer than 250 meters to be operated 24 hours a day. In practice, this means that a road traffic controller is always "watching" from a traffic control center. This person monitors the traffic situation, but also the (safety) systems of the tunnel. Because this person is not physically present and the tunnel contains many systems, he or she is helped by automated systems. Many tens of thousands of signals have to be monitored and interpreted in real time so that the road traffic controller makes the right traffic decisions. You can think of taking speed-limiting measures, breakdown assistance or even closing the tunnel.

The tunnel also exhibits autonomous behavior: in some cases it can already make predefined decisions based on signals. The right behavior Test manager Michel van Corven explains: "Although Ballast Nedam pays a lot of attention to the concrete work and the asphalt in the tunnel, the risks for our client lie much more in being able to operate the tunnel systems safely. For this, all systems must in all cases exhibit the correct behavior. From design to the end of the maintenance period, IXAS must continue to demonstrate this. In the past period, as a test manager, I worked with a team of specialists to demonstrate that the Gaasperdammertunnel shows the correct behavior. We have also resolved any remaining issues."

That work of the testing team is easier said than done: testing all possible combinations of detections and behavior can take years. After all, there are millions of combinations to be made. That is why not all combinations are tested, but all individual sensors. Van Corven: "We know that the behavior is continuously handled by the same 'software block'. If you know that the sensor works and that the behavioral treatment is always the same, you can perform a targeted sample and draw conclusions from it. That way you can build in certainty, without the tunnel having to remain closed for years. This working method is laid down in protocols drawn up and validated by teams of designers and testers."
We can build in certainty, without the tunnel having to remain closed for years to come.
Michel van Corven Test manager Ballast Nedam
Because IXAS is not allowed to determine for itself whether the tunnel is safe to open, validating the behavior is of great importance. Van Corven: “It has been precisely the validation that has taken a lot of work in the past year. We validate both the protocols and the tests themselves. A large number of civil servants involved also attend these tests, and with good results: the Environment Agency, Tunnel Safety Officer, Tunnel Manager, Traffic Control Center, the Municipality of Amsterdam and the Road Manager, among others, have ruled that the Gaasperdammertunnel can be "open". IXAS has built up a great deal of confidence here by communicating thoroughly and openly. The tunnel opens step by step. Two tunnel tubes were opened at the beginning of July and two more tunnel tubes will follow in the course of this year. ”

The switch track is the last step and will open when the A9 Badhoevedorp - Holendrecht project is completed. This project includes the road extension of the A9 at Ouderkerk aan de Amstel and Amstelveen and is an extension of the A9 Gaasperdammerweg. This project is expected to be completed in 2026. Both projects are part of the road expansion between Schiphol, Amsterdam and Almere.

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