Armadillos are invading Fremantle.

Not the South American mammal with the armour shell - though that is what they look like from above - but a new type of barrier for bike lanes.

And they are being tested along Parry Street as part of an investigation by the City of Fremantle to determine the best and most efficient type of bike lanes.

"We're going to look at a number of road treatments to decide which one is the safest for cyclists," Fremantle mayor Brad Pettitt said. "The armadillos represent quite a simple, and at about $60 each, an inexpensive way of creating a bike lane.

"Drivers who accidentally drift into a bike lane will soon realise the mistake they have made.

"And the armadillos are spaced so cyclists can exit and enter the lanes as necessary."

The armadillos, which are bolted to the road, have been successfully installed in cities across Europe and the US for several years. The Fremantle trial is a first for WA.

It is believed other councils are also looking at installing armadillos, including the City of Perth.

Their appeal is that they provide a better barrier between the motorist and cyclist than just a painted line and can be quickly installed.

They are also made from recycled materials.