**3. Conclusions**

The construction of highways in the Brazilian Amazonia is problematic because it faces nature-related, technical, economic, and environmental issues, which are interrelated.

The natural questions come from a range of origins, the main ones being geological-geotechnical, pedological, relief-related, and climate-related, and obviously cannot be gotten around given their territorial scope. The technical issues concern the natural subgrade, especially in floodplains (*várzeas*), formed by fine alluvial soils (silts and clays), which are plastic, impermeable, highly compressible, or expansive, present in the vast Amazon Basin. The economic issues are related to the costs of transporting stone material and lateritic soils—some with the presence of lateritic concretions (*picarras*)—to the construction sites since they occur in limited portions of the Amazonia (*terras firmes*). Environmental issues fall into a vicious circle since the construction of more highways tends to reach areas of virgin forest, which may be subject to new deforestation processes and other environmental impacts, affecting the rich fauna and flora of the region, in addition to native communities. Luckily, Brazilian environmental laws have become increasingly rigid, requiring in-depth studies of environmental impacts and public hearings before the construction of roadworks is licensed.
