38
The detailed quantitative data obtained during design by use of the maps,
supplemented by the photographs, and utilized in making the location compari-
sons are the items of construction, such as excavation, waste, borrow, over-
haul, stream channel changes and erosion protection; grade Separation, stream
bridges, retaining walls, drainage for surfaces of roadways and adjacent lands
and underground seepage, tunnels, and other structures; stabilization of road-
way in cuts and on fills and at structures; subbase, base, and surfacing mate-
rials; rights-of-way in relation to severance of properties and cost; traffic
service standards achieved; and the likelihood, in the future, of road failures
and the interruption of traffic services due to possible land slides; flood-
ing by extreme high water, snow slides, drift and deposition by wind onto road
surface of snow and sand, frost and thawing actions, and subsidence.
The initial design is revised by repeating, as necessary, applicable por-
tions of the preceding procedure to attain, insofar as feasible, every possi-
ble, practicable, and economical improvement in the design.
Utilizing the maps and all design criteria, mathematical descriptions are
prepared, in appropriate terms and details, of the horizontal alinement by cur-
vature, including circular curves (utilizing the degree of curve or radius as
designed), the central angle, semitangents, stationing of alinement points of
circular curves and spiral curves where used and length and bearing of tangents
Joining curves. Plane coordinates are computed of each point of intersection
(P.I.), point of change in curvature, intersection of centerline with property
lines, and intersection of rights-of-way lines with property lines. Descrip-
tions of rights-of-way are also computed. Utilizing the profiles, mathematical
descriptions are computed of the vertical alinement, including profile gradi-
ents by elevation of intersecting gradients, slope of the separate gradients,
and length of vertical curves.
The results of this procedure are a set of detailed construction plans
which guide the appraisers and negotiators in procuring needed rights-of-way,
the engineers in staking on the ground the highway centerline, slope stakes,
drainage, landscaping, highway structures and rights-of-way, and to guide the
construction forces in constructing the highway.
o 500 1,000 FEET
: ]
Stereogram of portion of highway route located in Stage l and
selected in Stage 2 for preliminary survey in Stage 3. The route
was placed on original photographs in Stereoscopic correspondence
with the topography by use of white acetate tape.
