One way in which poor communities are marginalized is lack of access- to public services, markets and employment opportunities- due to a lack of good roads. Many a time, the problem is the frequent damage to existing roads (rather than absence of roads).
A large part of the damage is water-related. (In Ethiopia, for example, runoff causes 35% of all road damage). At the same time, roads designed with disregard to local hydrology/water use are known to wreak havoc on agriculture and water security in communities they pass through.