There is increasing concern about the adverse effects of the road network on wildlife. The impacts of roads in the ecological landscape include habitat loss, habitat fragmentation and habitat degradation. These interrupt and modify natural processes, altering community structures and population dynamics. The large number of animal fatalities from road traffic accidents is also of concern. Only limited work has been carried out to investigate the intensity of these effects in the UK landscape. This study investigates the effects of roads on both small and large mammals and reviews mitigation measures that have been installed to ameliorate some of these effects. Roads of all sizes present a significant barrier to animal movement and they affect it in specific ways. Movement of small mammals is inhibited by lack of cover and the hostile road surface, whilst fragmentation of the road-verge by highway-related structures, impedes dispersal and compromises the benefits of connectivity often ascribed to such areas. Large animals, which use roads to travel through their territory, are more likely to be struck by traffic and are therefore, more directly affected by traffic-intensity. There is room for further mitigation to reduce the worst of the road-related impacts.