Performance-Based Analysis of Geometric Design of Highways and Streets (2014) / Chapter Skim
Currently Skimming:
Pages 44-60
The Chapter Skim interface presents what we've algorithmically identified as the most significant single chunk of text within every page in the chapter.
Select key terms on the right to highlight them within pages of the chapter.
From page 44... ...
44 C H A P T E R 5 5.1 Introduction This chapter presents the performance-based analysis application framework. This chapter describes how performance-based analysis can be used to inform geometric design decisions within multiple phases of the project development process and within or outside of an environmental review process.
|
From page 45... ...
Process Framework 45 5.2 Project Initiation The project initiation phase sets a foundation for understanding the project context and overarching intended outcomes. There are a variety of names for these activities depending on the transportation agency involved.
|
From page 46... ...
46 Performance-Based Analysis of Geometric Design of Highways and Streets The following subsections highlight activities and considerations for the two steps within the project initiation phase: 1. Project context 2.
|
From page 47... ...
Process Framework 47 • What are the current defining geometric characteristics? – Segment considerations ▪ Cross section (e.g., number of through lanes, turn lanes, medians, on-street parking, bicycle lanes, sidewalks, landscaping)
|
From page 48... ...
48 Performance-Based Analysis of Geometric Design of Highways and Streets At the root of such a project catalyst is the purpose of the project and a desired outcome from the investment. The desired outcomes help define design controls leading to appropriately selected criteria to meet targeted design and operational performance.
|
From page 49... ...
Process Framework 49 • What are the existing perceived or actual shortcomings of the highway or street? • How do the transportation elements best fit within the existing and future land use context?
|
From page 50... ...
50 Performance-Based Analysis of Geometric Design of Highways and Streets In some projects, solutions may evolve to a configuration or magnitude outside the intent of the original project outcomes. In these rare cases, project participants have had to re-evaluate and agree upon the intended project outcomes.
|
From page 51... ...
Process Framework 51 with implementing a roundabout, the designer may evaluate the performance qualities of other intersection forms and use performance categories and measures to help differentiate between concepts or design alternatives. Using the same basic example as above, further along in the project development process (e.g., 15% design)
|
From page 52... ...
52 Performance-Based Analysis of Geometric Design of Highways and Streets Potential design guidance applicable to a project can include a vast range of resources. For the purpose of illustrating some of the resources and examples of the range and diversity, these documents include the following: • AASHTO A Policy on the Geometric Design of Highways and Streets (1)
|
From page 53... ...
Process Framework 53 and assessing its financial feasibility, and guidance for deciding when to select an alternative or further refine alternatives are discussed in the following subsections. 5.4.1 Estimated Performance and Financial Feasibility The following subsections discuss steps to estimate performance of design choices and consider the financial feasibility of design alternatives.
|
From page 54... ...
54 Performance-Based Analysis of Geometric Design of Highways and Streets mobility performance of two-lane, two-lane divided, three-lane, and four-lane facilities is sufficient. In later stages, the impact of the specific horizontal alignment (e.g., curve radii, superelevation)
|
From page 55... ...
Process Framework 55 with fewer crashes but in mountainous or rolling terrain often result in more cut or fill and therefore higher project costs. To help further inform these types of decisions where tradeoffs between performance must be made, incorporating the financial feasibility or cost effectiveness of a project can be helpful in either selecting an alternative or refining one or more alternatives for continued analysis.
|
From page 56... ...
56 Performance-Based Analysis of Geometric Design of Highways and Streets 5.4.1.3 Interpreting Results from the Estimated Project Performance and Financial Feasibility The results from the steps to estimate the project performance and financial feasibility of the alternatives are intended to inform the geometric design decisions being made. Designers may choose alternatives that are not necessarily the most cost effective or even the highest performing relative to the preferred performance measure.
|
From page 57... ...
Process Framework 57 states have adopted their own variation for non-federal projects. State Environmental Policy Act processes may use different terms; however, the state processes generally follow those of NEPA.
|
From page 58... ...
58 Performance-Based Analysis of Geometric Design of Highways and Streets If a project does not qualify for a CE, the level of environmental analysis, documentation, and review progresses to an EA. 5.5.2 Environmental Assessment An EA is performed when the significance of impacts of a project is uncertain; an EA helps to determine whether a project will result in significant environmental impacts.
|
From page 59... ...
Process Framework 59 selection phases can be used to develop reasonable alternatives that perform to a level to fulfill the project's purpose and need while avoiding or minimizing environmental impacts. The evaluation and selection phase can also be used to help identify the preferred alternative.
|
From page 60... ...
60 Performance-Based Analysis of Geometric Design of Highways and Streets 5. Institute of Transportation Engineers.
|
Key Terms
This material may be derived from roughly machine-read images, and so is provided only to facilitate research.
More
information on Chapter Skim is available.