text: In addition to minimising construction cost, other factors influence the placement of cut or filled sections.
  For example, air pollutants can concentrate in the valleys created by the cut section. Conversely, noise pollution is mitigated by cut sections since an effective blockage of line-of-sight sound propagation is created by the depressed roadway design.
  The environmental effects of fill sections are typically favorable with respect to air pollution dispersal, but in respect to sound propagation, exposure of nearby residents is generally increased, since sound walls and other forms of sound path blockage are less effective in this geometry.
  The reasons for creating fills include the reduction of grade along a route or the elevation of the route above water, swampy ground, or areas where snow drifts frequently collect. Fills can also be used to cover tree stumps, rocks, or unstable soil, in which case material with a higher bearing capacity is placed on top of the obstacle in order to carry the weight of the roadway or railway and reduce differential settlement.