Basic Roadway Design
In the United States, we have been designing and building roadways for a very long time, and over the years our transportation engineers’ understanding of road geometry has become quite sophisticated.
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Basic Roadway Design
In the United States, we have been designing and building roadways for a very long time, and over the years our transportation engineers’ understanding of road geometry has become quite sophisticated. Geometric design deals with features of location, alignment, profile, cross section, and intersections for a range of highway types and classifications. Rural roads typically have fewer issues than urban roads. The geometric form and dimensions of the highway should properly reflect driver safety, desires, expectations, comfort, and convenience, and do so within the context of the surrounding landscape. State and federal agencies continuously fine-tune road geometry, and although the basic standards are pretty well set, there are still a lot of design options for creating green roadways. This chapter starts by looking at broader issues that affect basic roadway design—road types, safety concerns, right-of-way requirements, etc.—then focuses on the components that make up a green roadway.
Highway Administration (FHWA) because these roads are components of the National Highway System. They are the only class of road on which pedestrian and bicycle travel is prohibited. Entrance and exit ramps are the primary means of accessing freeways and other controlled-access facilities. There is not a lot of flexibility regarding the road geometry of interstate highways, but there are a lot of options for making the highway corridor greener and more attractive. Arterials and major collectors–Arterials and major collectors vary widely in character depending upon where they are constructed. Travel lanes of eleven or twelve feet are usually provided on arterials and major collectors. Minor collectors–Minor collectors are often designed for low-speed, low-volume operations. They are often designed to accommodate traffic between major collectors, arterials, and freeways.
Road Types Roadways can be classified as one of the following: Freeways/interstates–Freeway design standards for interstate highways are established by the Federal
Local roads–Local roads are generally constructed to comply with municipal requirements. However, the guidance provided for arterials and major collectors is suitable for local roads with high volumes and high speeds. Much like minor collectors, local roads are
J.L. Sipes and M.L. Sipes, Creating Green Roadways: Integrating Cultural, Natural, and Visual Resources into Transportation, DOI 10.5822/978-1-59726-322-1_3, © 2013 James L. Sipes and Matthew L. Sipes
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Figure 3-1 This is an example of a typical interstate highway exchange with on- and off-ramps and an overpass spanning the highway. Image acquired from depositphotos.com.
sometimes designed to provide shared accommodation for all users. Parkways–Parkways are typically located within parks or parklike settings that place an emphasis on natural resources, visual quality, and recreational opportunities. Parkways often have wider rights-of-way than other roads; this provides opportunities for pr
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