To deal with the increasing traffic, the city is turning to a pretty conventional solution: widening virtually the entire stretch of the highway that runs through the city.
But to deal with the noise — and the way that the highway has severed neighborhoods that were connected before it was built in the 1980s — Fast Company reports that the city has come to a pretty interesting solution: they're burying a few miles of the highway and covering it with parks, community gardens, and housing development.
The project, which is called the Hamburger Deckel and is projected to cost $800 million, comes after 20 years of lobbying from a local residents' initiative called "Ohne Dach ist Krach" (German for "No Roof, Too Much Racket"). Burying the highway is a practical way to meet a city noise abatement ordinance passed in 2005, as the sound barriers built in most places (including virtually everywhere in the US) can only cut down on noise by a factor of about half.
The tunnel project also has some other benefits: in covering what will be an eight-lane freeway, it'll provide a substantial amount of new parkland, along with space to build a neighborhood of 1700 homes. At its northern end, the new park will also link existing parkland, establishing a new greenbelt. Work is starting this year, and it's projected to be finished in 2022.
Of course, there's also another solution to eliminating traffic noise: tearing out urban highways entirely. In the US, Seattle is burying a downtown waterfront highway at a cost of $4.2 billion (and counting), and there's a pretty good case to be made that the city would have been better off removing the highway and replacing it with parks or pedestrian-friendly development.
But there are significant differences between the Hamburg and Seattle projects. One is that the Autobahn 7 is a crucial national highway that carries lots of traffic across the country — something that isn't true for Seattle's Alaskan Way Viaduct — making it much harder to tear down without major disruptions.
Additionally, Hamburg's project is less ambitious, in an engineering sense. Its highway is simply being slightly lowered, with a six-to-ten foot cap placed on top of it. Seattle is taking on the huge challenge of digging the widest deep-bore tunnel ever, 120 feet underground — which explains why the boring machine got stuck last year, halting construction until April at soonest and leading to cost over-runs.