Page 93 - Highway Engineering Handbook Building and Rehabilitating the Infrastructure

76 CHAPTER TWO

Slope review
Traffic control
Lighting
Waterline
Sanitary sewer
Final roadway, field and office check
This is not intended to be an all-inclusive list. The designer should contact the
government agency having review and final acceptance authority to see what reviews
are required during this phase of plan development.
Following acceptance of the final plans, specifications, and estimates, the project is
processed for letting. Any necessary consent legislation is obtained. The project is then
advertised, bids are taken, and the construction contract is awarded.

2.2 GEOMETRIC DESIGN

2.2.1 Design Controls
Once a route has been selected for a new highway, or a decision has been made to
perform major work on an existing facility, the next step is to establish the design
controls. The various factors considered for design controls may be generally
grouped into five categories: functional classification, traffic data, terrain, locale, and
design speed.
Functional classification is a way of grouping roadways together by the character
of service they provide. The initial division is between urban and rural roadways. The
urban classification may be defined differently in various parts of the country, but one
definition is incorporated areas having a population of 5000 or more (Ref. 1). Rural
areas are those areas outside of urban areas.
Each of these may be further subdivided into other classifications defined as
follows:
Interstate. Roadways on the federal system with the highest design speeds and
the highest design standards.
Freeway. An expressway with full access control and no at-grade intersections.
Expressway. A divided arterial highway with full or partial control of access and
generally having grade separations at major intersections.
Arterial. A facility primarily used for through traffic, usually on a continuous
route.
Collector. An intermediate roadway system which connects arterials with the
local road or street systems.
Local road or street. A road whose primary function is to provide access to
residences, businesses, or other abutting properties.
Traffic data are an important foundation in highway design. The information used
in design is usually a future forecast on the basis of existing traffic counts and expanded
on the basis of normal expected growth in the area or enhanced by estimates of future
business, commercial, or residential development. Most highway designs are based on