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waterway crossings, short and stable crossings at rivers and large streams, 
best access to intersecting roads, traversing marginal lands where possible, 
good and least drainage, and areas where traffic services are required. The 
types of qualitative controls to be avoided are plastic soils areas, swamps, 
poor drainage, and numerous waterway crossings, flood plains, landslide areas 
and unstable ground, specially used land, such as cemeteries, churches, facto- 
ries, public buildings, e.g., post offices, office buildings, and schools, and 
recreational areas, e.g., parks (unless purpose is to serve them), golf courses, 
and playgrounds. 
In addition to qualitative controls, quantitative controls are also deter- 
mined while the photographs are examined Stereoscopically. To determine dif- 
ferences in elevation, parallax measurements are made, and to determine lengths 
and position relationships, photographic coordinates are measured. Among the 
quantitative controls to be met and utilized are lowest saddles in topography 
and mountain passes; best bridge sites from standpoint of foundations, and 
length and height of bridges; minimum and most feasible profile gradients, hori- 
zontal curvature, cross sections and end areas, rise and fall; and good direct- 
ness. Among the quantitative controls to be avoided are excessively rugged 
topography, uneconomical bridge sites, excessive curvature, grades, cross sec- 
tions and end areas, and poor directness. 
Once all such controls have been determined and appropriately noted on the 
photographs, the feasible route alternatives are located and delineated there- 
on. Delineation is accomplished in such a manner, while the photographs are 
examined stereoscopically, as to place the routes where they will appear in 
stereoscopic correspondence with the topography in their intended position on 
the ground. 
Once this work is done, the positioning of each route is improved, espe- 
cially in alinement and grade, and in fitting topography and existing land use. 
Then, the photographs are copied and prints made for use in the field. With 
the copy prints in hand for stereoscopic examination, an inspection is made of 
the route alternatives where critical conditions were encountered which 
appeared to be unavoidable, such as swamps, poor drainage, landslide areas, 
land use severance, and expensive right-of-way areas. Such inspections are 
also made where confirmation is desired of photographic interpretation, aline- 
ment, gradients, cross sections, sunlight exposure, flood conditions, and like- 
lihood of snow drifts. 
As indicated and determined to be feasible from these field inspections, 
improvements in the route alternatives are made. Wherever maps are not avail- 
able and also where photographic background is desired, photographic mosaics 
are prepared of the area of survey. This is done to illustrate the land use, 
topography, and ground cover, to demonstrate the route alternatives in relation 
to each other, the land use, and topography, and to delineate the route con- 
sidered the most representative of the character of the highway route location 
possibilities between the designated termini. 
Next, segments of each route, which can be represented by a finite cross 
section of the ground and roadway, are selected. Each segment is selected by 
photographic interpretation, and the cross section to represent each section is 
determined by parallax and other measurements. Using each cross section and 
applying it to the segment it represents, a summation of all segments is made 
to ascertain probable construction quantities and right-of-way acreage. Uti- 
lizing the foregoing data, the probable cost of a highway on each of the routes 
is determined and a report prepared and illustrated. At the conclusion of 
this work, highway officials are aware of the problems and probable costs of 
locating and constructing the highway.