A flexible pavement is also called an asphalt pavement or Tarmac. Flexible pavement is composed of three or four layers. A four-layer flexible pavement includes a surface course, a base course and a sub-base course laid over a compacted subgrade. A three-layer flexible pavement omits the sub-base layer and places the base course directly on…
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Rigid pavements are often used for the construction of airport runways and major highways, including those in the highway system of the United States. They are also used for industrial applications such as harbor yard pavements, heavy vehicle parking locations and terminal pavements. Function and Design A rigid pavement is designed withstand all types of…
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The three-phase traffic theory was developed in the late 90s and overtook the existing theory which had only two phases. The older model considered free flow and congested to be the only two states that traffic could have. The three-phase model adds a very important intermediate phase called synchronized flow and renames the last phase…
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The efforts of the United States to design and build a national highway network began rather haphazardly with the passage of the Federal Aid Road Act of 1916. The Act allowed the provision of $75 million spread out over course of five years for matching funding to each state to create and maintain a national…
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Once the work of gathering data regarding road usage has been done the monumental task of analyzing it begins. In order to make sense of the numbers highway engineers will employ a number of different analytic methods to determine the needs of the community and what the best construction methods and design for a highway…
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When designing a highway there are several factors to consider, the main ones being geometric alignment, material choices, and structural design. Geometric Alignment Naturally, one of the most important things to consider when designing a highway is its physical geometry and proportions. To determine the physical layout that a highway will have to have engineers…
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The first step of any major public works projects, especially highways, is the collection and analysis of data. How this information is gathered and analyzed are hot topics and there are a wide variety of tools that highway planners have at their disposal to collect the information they need. Another issue arises when the question…
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When highway planning, development and construction requires funding, where does it come from? Fuel taxes are most often part of the revenue used. State highway revenues do not do well when generated by “general” taxes such as income tax, property tax, or other forms of “regular” funding. This is predominantly because these types of funding…
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Highway planning and development is an intricate, highly involved process during which must take a number of factors into consideration during the creation of a plan for new roadways. One of the most important aspects to be considered is the impact that any new development will have on the environment. This must be studied and…
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While our highways and roadways provide a very necessary and convenient means of travel, they also take a toll in lives lost. Approximately 1.2 million people are killed in traffic accidents annually and another 50 million are injured. Among persons under the age of 50, auto accidents are the number one cause of death. Highway…
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