Anyone who regularly drives on the N33 near Gieten or Rolde will be familiar with them: large metal constructions that stand across the road. They look like portals with signs attached to them, but they are missing. They are also not pedestrian bridges, cable racks or works of art. Yet they are there, firmly anchored and in several places along the road.
Anyone who thinks that the scaffolding was once intended for traffic signs or matrix signals is wrong. Rijkswaterstaat confirms that there were never plans to decorate the N33 here with large signs.
The portals are also not built for pedestrians or cyclists: there are no stairs or connecting paths attached to them. So the mystery remained intact for a while.
The key lies not with drivers, but with animals. Nocturnal animals even. The structures appear to have been built with a completely different road user in mind than us people behind the wheel.
If you pay close attention along the N33 after sunset, you can sometimes see something darting past in the twilight: bats. These small mammals use echolocation to orient themselves, but a wide highway poses a problem for them.
The asphalt is bare and empty, with no landmarks to focus on. This makes the road seem like a yawning void to the animals, and they prefer not to simply cross it.
The metal portals have been installed to prevent bats from flying lower and colliding with cars. They offer the animals something to hold on to in the air: a line that they can follow with their sonar and that allows them to cross the road higher.
The N33 is equipped with such structures in several places, so that the bats can continue to use their regular routes without the risk of colliding with traffic.
Since the first portals were installed at Gieten and Rolde around 2012, research has been conducted into their usefulness. Studies showed that bats do indeed use it, although not equally intensively everywhere. Sometimes they choose a natural route, for example a nearby row of trees or even a bicycle bridge that happens to run over the road.
According to Rijkswaterstaat, this is not a problem: what matters is that the animals have several safe options to cross. This greatly reduces the chance that they will skim low over the asphalt and be hit by traffic.
Do you ever have such a question when you are on the road or walking through your village? Feel free to send it to Find out! [email protected]. Then we dive in and who knows, you might discover that behind a mysterious structure along the road lies a whole story for bats.