A major target for environmental managers when trying to minimise the road-barrier effect on wildlife is to improve permeability to animal movements. Previous studies have demonstrated that drainage culverts are used by vertebrates, although knowledge of the main influencing factors remains limited. The use of 34 culverts from two roads in southern Portugal, differing in traffic volume, vehicle speeds and configuration, was evaluated by the analysis of terrestrial vertebrate footprint data (408 passage-operative days). Culvert crossings were related to various explanatory variables by means of canonical ordination techniques. We recorded 901 complete crossings, corresponding to an average of 2.2 crossings/culvert/operative day. Thirteen taxa were detected, all in more than one passage. Animal species included reptiles, small mammals, lagomorphs, carnivores and domestic dogs and cats.