Page 87 - Highway Engineering Handbook Building and Rehabilitating the Infrastructure

70 CHAPTER TWO

Scenic rivers. A study of the effect of the proposed transportation improvement on
any scenic rivers of state or national significance
Streams and wetlands. A study of the effect of the proposed transportation
improvement on streams and wetlands on project and abutting land areas
Water quality. A study of the effect of the proposed transportation improvement on
the quality of live streams or bodies of water

The next step is a refinement of feasible alternatives. This requires additional work
sufficient to prepare an environment document. This could include such items as approxi-
mate construction costs; alignment and profile studies; typical section development; pre-
liminary designs for geometric layout, drainage, right-of-way, and utilities; location of
interchanges, grade separations, and at-grade intersections; preliminary bridge designs at
critical locations; channel work; air, noise, and water studies; flood hazard evaluations;
and other supplemental studies and right-of-way information. Once again, input is sought
from the public sector through advertisement and public hearings.
Figure 2.1 shows the corridors for the feasible alternatives for an 11-mi relocation
of U.S. 30 in Ohio (Ref. 13). The map is part of a study evaluating crossroad treatment
for each alternative. Figures 2.2 and 2.3 show the projected crossroad treatments for the
various alternatives. The options are (1) interchange, (2) grade separation, or (3) closing
roads with cul-de-sacs. Since the proposed segment will be a limited-access highway,
the option of at-grade intersection was not considered. Figures 2.4 and 2.5 show current
and 20-year projected traffic volumes for all roadways. These are examples of maps
used in the study of feasible alternatives.
After consideration of all the input and comparing the benefits and disadvantages of
each alternative, the next step is to make a selection of the recommended alternative.
This selection is certified by the state’s transportation director. Following approval of
the environmental document, the project may proceed to the design phase.

2.1.5 Detail Design Phase
During the detail design phase, various design elements are finalized and construction
plans are developed. Project development in this phase can include many intermediate
reviews prior to final plan submission. These may include some or all of the follow-
ing, depending on the complexity of the plan:
Traffic request/validation
Traffic signal warrant analysis
Airway-highway clearance study
Alignment, grade, and typical section review
Conceptual maintenance of traffic review
Structure type study
Retaining wall justification
Service road justification
Preliminary drainage review
Preliminary right-of-way review
Bridge type, size, and location study
Drive review