CEMP-E
TI 850-02
AFMAN 32-1125(I)
1 MARCH 2000
e. When approaching points where a change in direction will occur, it will often prove useful to take an
extra wide cross section on the inside of the angle, as a curve must eventually connect the two tangents
through this area.
f. During the initial survey, be sure to take sufficient information to establish drainage paths on both
sides of the track. Also note paths that drain runoff into the right-of-way as well as outlets where water
can exit the right-of-way to nearby streams, drop inlets, or other runoff channels.
5. TRIAL LOCATION.
a. Trial location is the process of determining potentially practical routes (trial routes) through a
particular area. The objective of trial location is to produce the best combination of tangents, curves, and
grades for the routes surveyed. This is done by combining survey information with design and economic
guidelines, operating requirements, and engineering judgment. During this process, many factors must
be weighed and prioritized, and conflicting objectives must be balanced.
b. After the first trial routes are located, construction estimates are made. Then, the location (of the
track or drainage path) is usually modified in an attempt to reduce construction cost (while still
maintaining satisfactory operating characteristics) or to improve operating characteristics (while keeping
construction costs at a reasonable level). Adjustments are made to each route until the most satisfactory
set of compromises has been produced.
c. For track through an installation or in a terminal area, this process can usually be simplified and done
with fewer iterations. Likewise, the construction estimates might be done only once.
d. Trial location begins by lightly sketching the boundaries of the initial survey on a contour map. The
first trial route drawn through this strip is often done by minimizing grades, or in flatter territory, by
minimizing the number of curves needed. As with the initial survey, the route begins as a series of
connected tangents, with curves chosen and drawn in later.
e. After the route is sketched, a profile is drawn. The elevations of the railroad come from the
elevations of end and intermediate points and the different grades chosen between these points. The
elevations of existing ground level are obtained by approximating the point where the route would pass
through each cross section taken in the initial survey. When an initial survey is not done, the ground
elevations are taken from the points where the route crosses map contours.
f. With the trial routes drawn, earthwork and construction estimates are made using standard
procedures. At this stage, embankment and cut widths and slope angles may be estimated using the
typical roadway cross sections in chapter 6, paragraph 1. If one route does not yet appear clearly
superior, an additional iteration of modifications and analysis may be needed to produce the final location.
6. FINAL LOCATION.
a. To finalize the route selection, modifications may be made to the trial routes in an attempt to even cut
and fill amounts in adjacent areas or to reduce the total earthwork and grading required.
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