Changes in landuse, human settlement patterns or industrial development induced by the construction of transport infrastructure are secondary effects. New settlements and housing estates may follow the construction of new regional roads and in turn induce the construction of local access roads. These secondary effects are usually outside the responsibility of the transport sector, but should be considered in Strategic Environmental Assessments (SEA) and Environmental Impact Assessments (EIA) (see Chapter 5). In areas where secondary linear development along existing road networks is a major threat to important wildlife conservation strategies, traffic calming measures or road decommissioning may be necessary (see Chapter 7).

One of the main secondary threats associated with infrastructure development is the increased degree of human access and disturbance. Networks of small forest roads provide hunters and tourists access to otherwise undisturbed wildlife habitats. Some design specifications have purposely not included car parking facilities and lay-bys to minimise disturbance to sensitive habitats such as coastal marshes important for waterbirds. However, once infrastructure development has occurred it is very difficult to limit access to adjacent land even if it is of high conservation value. Plans to manage increased access should therefore be drawn up during the planning stage and implemented in association with the infrastructure development.