Biking under the tracks

In 1902, the city of Berlin opened its underground or "U-Bahn" train line to the public. The word "underground" is somewhat misleading however, since large parts of the line were actually built above ground as an elevated railway. The U1 as it it called today, runs across much of central Berlin for 9 kilometers and its bright yellow train cars rattling along above the busy streets are an iconic part of Berlin's cityscape on par with the Brandenburg Gate or the TV Tower.

The space underneath the viaduct, however, is a grim place, dominated by grey concrete, soot and parked cars. It's not a place to linger. But a small group of Berliners realized that it has serious potential.

"We saw this charming architecture, which lies idle and we thought that it could be used better," Matthias Heskamp told DW. The Berlin-based architect is one of the eight people behind the Radbahn ("bike train") project, which wants to turn the space into a bike path - a very unique one.

"We want to use the existing infrastructure and the space below the U1 offers a lot of benefits for a bike path: It is protected from rain or snow, but also from car traffic," says Heskamp. The U1-tracks are flanked by two lanes of road traffic on both sides for most of the way. In some sections there is also a bike path added on the outside, but it is bumpy, narrow and competes for space with the pedestrians on the sidewalk.

The sheltered bike path under the train, on the other hand, would be more like a real road for cyclists with far fewer intersections to cross than on the current bike paths. The plan also envisions intelligent traffic management. "We want to negate the need for people to race and then have to wait at the next traffic light," says Heskamp. Instead, displays will inform bikers about the optimal speed to ride in order to keep hitting green lights at all the intersections.

But the ideas don't end there. The international group of activists with backgrounds in a variety of fields also hopes that the space beneath the train will become an innovative urban space, where small outdoor cafés or bike repair and rental shops could establish themselves. They would also like to integrate an energy harvesting technology that generates electricity when bicycles role over the pavement, similar to Dutch artist Daan Roosegaarde's sustainable dance floor.

"This bike path could have a signal effect for urban development, a bit like the High Line in Manhattan," Heskamp says. The High Line, an abandoned elevated train track on Manhattan's West Side, was turned into a pedestrian park a few years ago and has revitalized the entire surrounding area.

Admittedly, there are a few obstacles along the way for the U1 bike path project. There are minor ones like occasional sets of stairs that would have to be converted into gently inclined ramps, but also bigger ones like a shipping canal. But the good news is that the viaduct carrying the U1 already crosses the canal, so the Radbahn team suggests hanging a bike bridge from the viaduct in that particular spot. Structurally no problem, they say.

Overall, costly measures like this bridge are the exception and the Radbahn team estimates that 80 percent of the route would only require minor investment. That is easy to believe when you take a closer look: If it wasn't for the parked cars, biking under the viaduct would already be feasible in many places even now.

Despite the obvious appeal of the concept, the reaction of Berlin's government to the proposal was lukewarm at best. "In principle, we are always open to supporting bicycle traffic with good ideas but we also have to consider the feasibility and financing," said Martin Pallgen, spokesperson for Andreas Geisel, Berlin's Senator for Urban Development and the Environment.

There are concerns about a seamless integration of the Radbahn with bike traffic in its vicinity, that the space might not be wide enough for extensive bike traffic travelling in both directions and that Berlin's public transportation system occasionally needs to access the space for maintenance work on the elevated tracks.

Initially it looked like the Radbahn wouldn't happen, but in November 2015 the project won the prestigious German Federal Ecodesign Award, providing it with new momentum. Berlin's city council has now comissioned a two-year feasibility study to see if the innovative bike path might just work.