Swiss Federal Road Administration developed ASTRA prefabricated bridge for organization of detour of the repaired section of the highway. Drivers can continue driving over the work site with virtually no speed reduction, and the construction workers and the new asphalt are protected from rain and snow.
The installation of the ASTRA bridge requires a temporary closure of traffic, but this can be done on weekends, when the flow of traffic is reduced . Several sections of the bridge are delivered by truck and installed overnight above the planned work area.
Astra prefabricated bridge
The structure is equipped with smooth entrances on both sides , which allow cars to move up and down the overpass without any problems. The current version of the ASTRA is just over 257 m long and 7.57 m wide. This allows vehicles to travel on the flyover in two lanes. Speed is limited to 60 km/h.
Developers note that after the bridge is installed, workers no longer need to monitor the flow of traffic. In addition, the height of 4.65 m gives the builders enough space to work under the roadway and also protects them from heat and rain. As the work does not interrupt traffic, it can be carried out particularly during the day.
When work on the site is complete, hydraulic lifts can raise the bridge several inches (10 cm) and move it forward to begin the next work areas.
In 2022, when the ASTRA bridge was tested for the first time, it was not possible to normalize the traffic flow. After that, the structure was improved by adding ramps, which reduced the slope of the ascent from the former 6% to 1.25%.