Green bridges make a significant contribution to the preservation of biodiversity. They connect separate habitats and allow animals to move freely, which is essential for their reproduction and genetic diversity. Deer, wild boar and lynx migrate many kilometres every day and therefore need plenty of room to move. Smaller animals also use these bridges. Without such corridors, many animal species are forced to cross dangerous roads, which often leads to fatal accidents. Green bridges also promote the recolonisation of areas that have been isolated by human activity. Another benefit is the reduction of wildlife accidents. The safe crossing of roads not only protects the lives of animals, but also reduces the risk for motorists, which has a positive impact on road safety.

Construction measures and the role of PORR

The construction of a green bridge requires careful planning and execution. The bridges must be wide enough to allow safe passage for various animal species and covered with vegetation that mimics the animals' natural habitat. In addition, fences must be erected along the roads to prevent the animals from crossing the road and guide them to the bridge.

PORR has provided an impressive example of the successful construction of such a structure with the ‘Pforzheim Green Bridge’ project. This bridge, which crosses the A8 motorway, connects important habitats in the Black Forest with the Swabian Alb and makes them safely accessible to animals.

Practical example: Pforzheim green bridge with integral bridge arches

The ‘Pforzheim Green Bridge’ project shows how technical expertise and nature conservation go hand in hand. In future, wild animals will be able to cross the A8 motorway safely on the 64 m long and 53 m wide integral arch bridge. The green bridge is designed as an integral arch bridge and is founded on transom foundations. Highly absorbent irritation protection walls shield the crossing animals from traffic noise and glare. As the six-lane extension of the motorway is taking place in parallel, the PORR team had to follow the traffic phases of the main construction project ‘Enztalquerung’. The solid arch was therefore erected on one side at a time and supported in the centre. This meant that once the first bridge arch was safely resting on its 12-metre-high shoring, the bridge construction work could continue after a planned construction break of several months. Each half-arch was constructed in six concreting sections. For the final concreting of the 1.5 m wide gap closure, hydraulic presses raised the two bridge sections by 2 to 6 cm. Once completed, it will also provide a safe habitat for numerous regional animal and plant species.

Green bridges are an indispensable instrument in modern nature conservation. They contribute to the preservation of biodiversity and promote the recolonisation of isolated habitats. They also increase the safety of road users. PORR's ‘Pforzheim Green Bridge’ project is an excellent example of how such structures can be successfully realised. It shows that technical innovation and nature conservation do not have to be opposites, but complement each other. With projects like this, PORR is making a valuable contribution to the ESG (Environmental, Social, and Governance) goals and to protecting our natural environment as well as promoting a sustainable future.