Estimated reading time: 3 minutes, 50 seconds.
Our road network is inconceivable without bridges and tunnels. They help save time in overcoming hurdles and bottlenecks and contribute to making traffic and transportation more effective, safer, and eco-friendlier. In an interview with our colleague Georg Mayer from PTV Transport Consult, we took a closer look at these key elements of the road network.
Compass: Bridges and tunnels are a natural part of our road networks. The importance of the role they play only becomes apparent when they fail …
Georg Mayer: Due to topographic conditions, bridges and tunnels frequently have a bottleneck function. When they are closed due to restoration or service work or as a result of construction failure, then an important route may only be available to a limited extent or perhaps not at all across a longer period of time. This usually has grave consequences for traffic flow and can result in significant costs. A few years ago, when a pier on the Schiersteiner Bridge on the A643 sank and the bridge had to be closed, this caused significant traffic restrictions in the entire Mainz/Wiesbaden region. Another current example is the sudden failure of the bridge in Genoa, Italy.
Compass: You and your colleagues at PTV Transport Consult have been working on research projects on precisely this topic in the last few years, haven’t you?
Georg Mayer: Yes, on the one hand on the national level on the SKRIBT research project (SKRIBT stands for “Schutz kritischer Infrastruktur, Brücken und Tunnel [protection of critical infrastructure, bridges and tunnels]). Here, the effectiveness of suitable protective measures for infrastructure was being examined. On the other hand, we were managing the European research project SeRoN (Security of Road Transport Networks) Here, we examined in various countries what happens if particular structures fail and we developed a method that enables the responsible institutions to assess road infrastructure elements.
Compass: Are bridges and tunnels particularly sensitive to disturbances?
Georg Mayer: No more than other structures. However, there are some factors that you have to consider with respect to bridges. The increased traffic, for example. It’s safe to assume that heavy traffic will be as much as 40% higher in 2030 than it was in 2010. Many structures are not designed for such heavy traffic. Climate change is also playing a role. Increased heavy rain and periods of heat like the ones we had this year can affect construction. This is why infrastructure elements such as bridges and tunnels must be checked and monitored regularly.
Compass: Despite regular monitoring, you can never rule out accidents completely …
Georg Mayer: No, that’s why it’s important to develop appropriate failure strategies early on, in order to minimize effects on traffic in case of emergency. My motto is “Consider first, don’t consider only after the fact.”
Compass: What do such safety examinations look like?
Georg Mayer: The basis are so-called quantitative risk analyses. We at PTV Transport Consult analyse the possible external effects on traffic infrastructure as well as typical damage scenarios. We assess the risks and then define measures to prevent damage and deal with incidents. For example, in tunnels, fires present a great potential danger. With simulations, we can detect the weak points – with respect to smoke development and spread, for instance. By linking traffic flow and pedestrian simulation (for which we use the PTV Vissim software provided by our corporate group), escape behaviour can be mapped and the evaluation planned and checked. This way, rescue measures can be optimised.
Compass: Are such risk analyses suitable not just for newly-built, but also for existing structures?
Georg Mayer: With our examinations, we are frequently incorporated at an early planning stage in order to find the best solution at the beginning. However, a risk analysis also makes sense when the focus is on the maintenance and enhancement of structures. Cost-benefit analyses are a keyword here. Then there is also the question whether a particular measure really results in a significant safety increase or is sooner “nice to have” and primarily increases costs.
Compass: Do you have a current example?
Georg Mayer: PTV Transport Consult just participated in a project in Hamburg. The motorway A7 is being expanded to eight lanes there. Because the route passes close to residential areas, extensive noise protection from tunnels is planned. There was an initial, truly costly suggestion for how ventilation in these tunnels could be achieved. With our risk analysis, we were able to show that a simpler measure, namely very short emergency exits between the tubes, could even produce a higher level of safety. This measure is now being implemented, just as we suggested.