From 1970 onwards, Cochlearia danica has spread considerably along motorways in the Netherlands. Similar observations have been made in surrounding countries. The increase of the species is presumably caused by a change in road management, leading to an increase of de-icing salts during winter. The settlement of Cochlearia danica along a section of a motorway has been studied. It appears that the first settlements usually occur near intersections and viaducts; in the following years the species spreads massively along the road sections in between, nearly exclusively on the central reservation. The abundance of the species is highest in the centre strips; the soil permeability is relatively small here, so that the salt is not leached out by rainwater.