Structure of route location process

Route location is done in a funnel-like sequence, moving from a large area to a single centre line. Each step narrows the area and increases the detail of the study.

 Region  (whole area between terminals)
   |  map study, aerial photos
 Band    (feasible strips, obstacles removed)
   |  reconnaissance
 Corridor (probable narrow routes)
   |  preliminary survey
 Alignment (single centre line, final location)

1. Region: the whole area of interest between the two terminals, including the controls. Identified from small-scale maps.
2. Band: the part of the region left after eliminating zones with obstacles (mountains, big lakes, forests). Studied by maps and air photos.
3. Corridor: within the band, the narrower strips containing the likely alignments - width a few hundred metres to a few kilometres. Selected after reconnaissance.
4. Alignment: within the chosen corridor the exact centre line is fixed after preliminary and detailed surveys.

Process steps: (i) identify the terminals and obligatory points, (ii) map study, (iii) reconnaissance survey, (iv) preliminary survey, (v) final location/detailed survey, followed by design and cost estimate.