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The Zurich west bypass - high-tech products for road tunnels

Over 13 km of safe, reliable tunnel infrastructure

The N4/N20 Zurich west bypass, in Knonaueramt, Switzerland, is 24 km long, of which some 13.5 km are tunnels. The Islisbergtunnel, the last of five tunnels, rounded off the work on the west bypass in 2009 - pleasing inhabitants of the area, commuters, and tourists. Through traffic was greatly reduced in nearby areas with its opening.


Safety, operation, cost-effectiveness, and high availability in the tunnel  

Safety, operation, cost-effectiveness, and high availability in the tunnel

Monitoring and operating a tunnel are very complex tasks. The challenges facing the operating and safety equipment are demanding. Parts of the system need to communicate with each other seamlessly and consistent operation of tunnel systems is an absolute must.

Pöyry Infra AG, a Zurich-based renowned planning firm in the infrastructure sector with around 280 engineers and specialists, took on the planning, organization, and implementation of this challenging task.

Particular value was placed on the planning and implementation of modern, future-oriented technology and products. The entire order for supplying electromechanical components for distributed I/O devices was placed with Phoenix Contact thanks to the company's good reputation. Bus couplers and I/O modules for parts of the operating and safety equipment were among the devices ordered.

Phoenix Contact products had previously been used and tested in other projects, such as the Kirchenwald tunnel. The impressive component performance, as well as the advice and support received from Phoenix Contact employees finally led to the implementation of our technology throughout the length of the tunnel.


Phoenix Contact components were implemented in many areas of the west bypass - tunnel airing and ventilation, lighting, power supply for the control room and emergency systems such as safety door control.

A higher-level control system controls the modules used from a central location. Airing and ventilation in the tunnel is carried out via the distributed I/O modules used in the Inline system kit. This enables easy conversion or replacement without any need to interrupt operation.

The QUINT POWER power supply units are suitable for universal and worldwide use thanks to the wide-range input of 85 to 264 V AC. Even in the event of power failures up to 20 ms, QUINT POWER still provides the full output. To this end, Power Boost controls preventive function monitoring via the power reserve, thereby ensuring an uninterrupted power supply.

The availability of all components is significantly increased by using surge arresters.

In the Kirchenwald tunnel project, the connection doors can be safely opened and closed in the event of an emergency, using safety devices from the PSR product range.

The tunnels in both directions are connected via a cross passage, enabling access for rescue in the case of emergency through the unaffected tunnel - this tunnel, however, must always be kept closed.


Phoenix Contact supports the most important functionalities in the tunnel system, such as safety, operation, cost-effectiveness, and availability. Different products are used to meet these goals, including PROFIBUS converters, programmable logic controllers (PLCs), bus couplers, DIN rail-mountable power supply units, thermomagnetic circuit breakers, and surge protection.

When building the Zurich west bypass, particular attention was always placed on continuing cooperation and ongoing technical development. In this way, an efficient solution was found and implementation was a success.

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  • The Zurich west bypass - high-tech products for road tunnels
  • Tunnels


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