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Approach and Core Principles of CSS Design
"For each potential project, designers are faced with the task of balancing the need for the highway improvement with the need to safely integrate the design into the surrounding natural and human environments. In order to do this, designers need... more
Federal Highway Administration (FHWA),
from Flexibility in Highway Design |
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Bridge Design Elements: Introduction
"...bridges are viewed from two perspectives. Traveling
over the bridge deck, the driver of a vehicle sees the travelway, bridge railings, and
the view to either side. If the bridge crosses over another roadway, water or land
both on its side and... more
Federal Highway Administration (FHWA),
from Flexibility in Highway Design |
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Citizen-Generated Design Plans
In "Citizen-Generated Design Plans," Donal R. Simpson describes a process whereby communities hired their own design professional to help them to develop design plans that "successfully bridge the communications gap between citizens and highway... more
Project for Public Spaces (PPS),
from Community Impact Assessment |
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Considering Scale
People driving in a car see the world at a much different scale than people walking on the street. This large discrepancy in the design scale for a car versus the design scale for people has changed the overall planning of our communities.
Federal Highway Administration (FHWA),
from Flexibility in Highway Design |
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Context Assessment
In order for a designer to be sensitive to the projects surrounding environment, he or she must consider its context and physical location carefully during this stage of project planning. Some of these issues to be considered are; the physical... more
Federal Highway Administration (FHWA),
from Flexibility in Highway Design |
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Cross-Section Elements: Clear Zones
A clear zone is "the unobstructed, ... flat area provided beyond the edge of the traveled way for the recovery of errant vehicles ... The width
of the clear zone is influenced by ... traffic volume, design speed of the highway,and slope of the... more
Federal Highway Administration (FHWA),
from Flexibility in Highway Design |
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Cross-Section Elements: Utilities
Public utilities are a often overlooked but important element of crossection design. "Overhead utilities typically include electric, telephone, and cable television. For new construction in urban areas, electric, telephone, and other... more
Federal Highway Administration (FHWA),
from Flexibility in Highway Design |
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Cross-Section: Restricted Right-of-Way
"Many roads currently exist that were not built to todays standards. These roads
may be located in restricted right-of-way corridors that have scenic or historic
resources adjacent to the roadway. It is necessary to try to avoid impacting these... more
Federal Highway Administration (FHWA),
from Flexibility in Highway Design |
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Design Speed
"All geometric design elements of the highway are affected by design speed. Some roadway design elements are related directly to and vary appreciably with design speed such as horizontal curvature, super-elevation, sight distance, and gradient. The... more
Federal Highway Administration (FHWA),
from Flexibility in Highway Design |
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Detailing the Design
Particularly during the final design phase, it is the details associated with the project that are important. Employing a multidisciplinary design team ensures that important design details are considered and that they are compatible with community... more
Federal Highway Administration (FHWA),
from Flexibility in Highway Design |
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General Guidelines for the Geometrics of Bridge Design
"Bridges and other related major structures play an important role in defining the manner in which a highway affects the aesthetic, scenic, historic, and cultural resources of the corridor within which it is located....The geometric criteria in the... more
Federal Highway Administration (FHWA),
from Flexibility in Highway Design |
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Horizontal and Vertical Alinement
Road Alinements need to be consistent with topography, preserve developments along the road and incorporate community values. The horizontal and vertical alinements are best addressed in the preliminary design phases of the project.
Federal Highway Administration (FHWA),
from Flexibility in Highway Design |
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Peak-Hour Level of Service
Level of service is a grading system for amount
of congestion, using the letter A to represent the least amount of congestion and F to
refer to the greatest amount. The appropriate degree of congestion (that is, the level of service) to be used in... more
Federal Highway Administration (FHWA),
from Flexibility in Highway Design |
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Placemaking
"Placemaking strives to balance all the users of a street - pedestrians, transit riders, motorists, and bicyclists, rather than on just designing roads to accommodate motor vehicles. The focus is on how these streets and roads connect to the... more
Project for Public Spaces (PPS),
from How Transportation and Community Partnerships are Shaping America: Part I: Transit Stops and Stations |
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Project Development
After a project has been planned and programmed for implementation, it moves
into the project development phase. The basic steps in this stage include the following: refinement of purpose and need, development of a range of alternatives (including... more
Federal Highway Administration (FHWA),
from Flexibility in Highway Design |
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Road Width
The design element with the greatest effect on the scale of the roadway is its width, or cross section. Elements (or a lack of elements) along the roadside also contribute to the perceived width of the road and can even affect the speed at which... more
Federal Highway Administration (FHWA),
from Flexibility in Highway Design |
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The AASHTO Green Book
AASHTO Green Book contains a general set of guidlines on road design, however, it is not meant to be a design manual. A great deal of flexibility is allowed, and designers are encouraged to tailor roads to particular situations.
Federal Highway Administration (FHWA),
from Flexibility in Highway Design |
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Tort Liability
Tort liability: definition and procedures according to AASHTO Green Book, federal highway and state regulations.
Impact of tort liability procedures on innovation.
Federal Highway Administration (FHWA),
from Flexibility in Highway Design |
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Types of Highway Improvement Projects
There are four basic types of physical improvement projects, some of which must comply with standards and others that do not have to comply. These types of improvement projects are discussed in the following paragraphs.
Federal Highway Administration (FHWA),
from Flexibility in Highway Design |
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What the Green Book Does Not Contain
The Green Book is not a design manual. It provides guidance on the geometric dimensions of the roadway. This includes widths of travel lanes, medians, shoulders, and clear zones; the width and shape of medians; turning radii; and other dimensions.... more
Federal Highway Administration (FHWA),
from Flexibility in Highway Design |
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