The ASTRA Bridge is a mobile auxiliary bridge suitable for use during roadworks. While roadworks are being carried out under the bridge, traffic can be re-routed over it. This allows roadworks to be carried out during the day without closing any carriageways or diverting traffic. Nor is there generally any need to close lanes or reduce lane widths or speed on the opposite carriageway, while the length of the roadworks site can be kept shorter.
Despite these benefits, the use of the ASTRA Bridge also brings with it some challenges. These include assembling and dismantling the bridge on the carriageway and the space required to store the bridge parts. In addition, the bridge can only be used on certain motorway sections. This is an innovative approach to road maintenance technology, which is why experience is being gained in a pilot project on the A1 between Recherswil and Luterbach.
The ASTRA Bridge was first used on the A1 between Recherswil and Luterbach in 2022. During this pilot project, it was confirmed that the bridge works both conceptually and technically, and that roadworks under the bridge can be carried out as planned both in terms of schedule and quality. The automatic repositioning of the bridge was also a success and traffic could drive over the bridge without incident. Roadworks could be carried out during the day – which meant less construction noise at night and more socially acceptable working hours – and it safely separated traffic from the work being carried out under the bridge.
However, the flow of traffic during the pilot project was not as smooth as had been hoped for, which is why the ASTRA Bridge is being optimised. In particular it became apparent that the gradient of the entrance and exit ramps for heavy goods vehicles was not satisfactory, requiring the ramp rounding, i.e. the change in gradient, to be improved in order to enhance comfort and speed when driving.
The planned optimisation was tested at the Wiggertal junction storage location near Rothrist in September 2022. The new radius of curvature was simulated with a road surface coating. Various vehicles, including sports cars, caravan trailers, motorbikes and loaded trucks, i.e. vehicle transporters and double-decker trucks, drove over the optimised ASTRA Bridge and they could all travel over it at 60 km/h without difficulty.
The positive test results now make it possible to plan the structural adaptation of the ASTRA Bridge. This bridge is an investment in the future, which is why ample time is being invested in the sophisticated engineering work. Once the mobile bridge has been structurally adapted, tests will be repeated and operating personnel will receive training.
Against this background, the ASTRA Bridge is scheduled to be used again on the A1 section between Recherswil and Luterbach on the carriageway towards Zurich starting spring 2024. Until then, no work will be carried out on this section of motorway.