Road ecology is a recent branch of Conservation biology that studies the effects of roadnetworks and motorized traffic on biodiversity and ecosystems. The most investigated impacts are road-kills and barrier effects, but most studies are descriptive approximations. Contrarily, the primary purpose of Road ecology should be to determine the mechanisms producing road-related impacts, with the aim to plan the most suitable mitigation measures. The main objective of this thesis was to produce a relevant contribution to Road ecology, suggesting how to investigate the mechanisms potentially determining road-kills, barrier effects and the effectiveness of mitigation measures, but also increasing the knowledge about little-known road-related impacts such as changes in behavior and biological invasions. The first chapter of this thesis aimed to determine the life history, temporal and spatial factors affecting road-kill probability for vertebrate species in a Mediterranean landscape (Doñana Natural Park, southwestern Spain). Abundant species were more road-killed than rare species, but also ectotherms had higher road-kill probability than endotherms (including birds). Species abundance was also the most relevant factor determining road-kill probability (both temporally and spatially) for different functional groups of species (for example resident, breeding, wintering and migrant birds in the temporal analysis and small passerines in the spatial analysis). The second chapter was the first study investigating the factors determining barrier effect along a heterogeneous roadnetwork (ie paved and unpaved roads with different traffic intensity). Our study area … Palabras clave: Population