Controlled-access highway

Not only larger animals but also small animals are not supposed to be on the controlled-access highway. The small animals can also be irritating for motorists and provoke accidents. Small animals that are run over can also attract larger animals such as foxes or crows, which somehow get onto the controlled-access highway despite the fence. Unfortunately, the controlled-access highway is not secured for amphibians and small animals in many places (cf. Figures 1 and 2).

Figure 1: Controlled-access highway without amphibian fence
Figure 2: Amphibians and other small animals easily pass through the large animal fence.

Unfortunately, amphibians being run over are often no longer recognizable after a few cars. With smoother surfaces on controlled-access highways the animals dissolve more quickly than on conventional roads (cf. Figures 3 and 4).

Figure 3: A frog being run over on the conventional road is soon no longer recognizable.
Figure 4: Another frog being over run on the conventional road is already no longer recognizable.

The amphibian fence along the highway also features an overhanging fold to provide over-climbing protection (cf. Figure 5).

Figure 5: Amphibian fence along the controlled-access highway A1 in Effertikon (Canton of Zürich)

Accidents with migrating frogs on controlled-access highways have occurred in Greece, for example. Numerous motorists have been surprised by migrating frogs near Langadas (cf. Figure 6). The frog colony had forced a closure of a major controlled-access highway for two hours after three motorists ran off the road while trying to avoid the frogs.

Figure 6: Frogs on the Egnatia highway in northern Greece
© Nikolas Giakoumidis


Small or large animals have no business on the controlled-access highway. Animals that are run over can also attract birds and other larger animals, which sometimes climb over the fence or dig through it at the bottom. Ultimately, it is also a question of ethics and not just traffic safety.