The request from the Swiss highway operator ASTRA was precise: to allow traffic to flow on two lanes even when working to renew the road surface. To find a practical and safe solution, a European tender was launched, won by a temporary association of three companies.
The winning project is called Astra Bridge: a mobile bridge on wheels that creates a temporary elevated traffic lane, with workers safely working on the "lower level". The bridge is 240 meters long and is made of sections. The special modular structure allows it to be placed not only in a straight line: the bridge is able to form an S-curve with a radius of 1,000 meters, thanks to the possibility of steering each module at the joint.
The project has been developed and successfully used in various parts of Switzerland after a first, less satisfactory, trial in 2022. The too-steep access ramp caused cars to slow down drastically, creating traffic jams.
In the revised version, the ramp's incline was significantly reduced, allowing access to the bridge at the recommended speed of 60 km/h. In a second test on April 7, the structure "did not cause any change in traffic and in almost three weeks of operation, it did not even compromise the traffic flow," announced USTRA, the Federal Roads Office, in a statement. This is a decidedly high traffic volume: on the affected road section – towards Zurich – an average of about 73,000 vehicles pass through each day, and over 82,000 on peak days.
The construction of the complete steel structure required 38,000 working hours, a number of hours – specifies Jörg Senn, CEO of one of the companies involved in the project – which "translates into approximately 15 man-years of work." But now it only takes two nights of assembly to get the structure fully operational; a 100-meter long, 5.2-meter wide, and 3.1-meter high corridor opens under the bridge.
Several European countries – including Norway, Japan, and the Netherlands – have already shown great interest in Astra Bridge, and the Swiss authorities have declared their willingness to share this innovative technology, which is not covered by a patent.
