AASHTO FHD-1 pdf free download
AASHTO FHD-1 pdf free download.A Guide for Achieving Flexibility in Highway Design.
Departments of Transportation (DOTs) and other transportation agencies utilize a range of terminology to describe their process. The process outlined in Figure 1-1 and the terminology employed here are generally accepted. For the purposes of discussion, the process and terminology are as follows:
• Concept Definition—The identification of a project, including its need, geographic limits, and other specifics to enable studies to begin.
• Planning and Alternatives Development—The broad range of activities that result in the selection of a preferred plan that meets regulatory requirements and is sufficiently detailed to proceed with final design and construction.
• Preliminary Design—The initial stage of the final design process to confirm right-of-way needs.
• Final Design—Completion of design documents and specifications for construction of the project.
1.1.1 Concept Definition
In the concept definition stage, the purpose and need for a project or improvement is identified. Such need may come from regular performance monitoring (e.g., pavement condition, congestion, safety history), from a local governmental request made necessary by actions of others (e.g., in response to land use changes or development), by legislative direction, or by response to an emergency. Concept definition involves defining the need and purpose of an improvement, the limits of the project, and often the schedule and funding of the project.
A key to context-sensitive planning and design is developing a clear understanding during concept definition of the need for a project, which involves an understanding of the transportation problem and the context of the project area that requires addressing. In short, the concept definition stage represents an important decision of project stakeholders to take action by committing to solving a problem on a specific route or in a specified area or corridor. The details of the solution(s) are arrived at in subsequent project development stages.
11.2 Planning and Alternatives Development
The planning and alternatives development stages involve that part of the process in which alternatives are proposed and studied, environmental and community impacts are assessed, and decisions are reached about the key physical, environmental, community need, and operational aspects of the proposed project. During this stage, the greatest opportunities and challenges for a flexible transportation solution occur.
Once the purpose and need for a project have been determined with public input, design criteria are selected by the transportation agency and reviewed with the project stakeholders. Note that this occurs early in the overall project development process. The basis for the project design criteria will generally be the transportation agency’s design guidelines. Project design criteria should recognize both the functionality of the roadway improvement (its use once it has been improved) and the values of the community.
During the planning and alternatives development stages, designers, working with planners, environmental specialists, the public, and agencies, have the greatest latitude to propose, study, and evaluate a full range of alternatives. Clearly, it is during this stage of the project that the designer can have the greatest influence on the quality of the design, which includes not only its trafficcarrying capability and safety performance, but also its effects on the community and surrounding land uses.AASHTO FHD-1 pdf download.
