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Some noteworthy AASHTO publications are: [9] A Policy on Geometric Design of Highways and Streets, often called "The Green Book" because of the color of its cover. This book covers the functional design of roads and highways including such things as the layout of intersections, horizontal curves, and vertical curves.
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In 1994, the AASHTO Green Book [1] defined the operating speed as "the highest overall speed at which a driver can travel on a given highway under favorable weather conditions and under prevailing traffic conditions without at any time exceeding the safe speed as determined by the design speed on a section-by-section basis," a definition which ...
The concept of design speed is evolving. The definition in the 1994 edition of the AASHTO Green Book, [10] was "the maximum safe speed that can be maintained over a specified section of highway when conditions are so favorable that the design features of the highway govern. The assumed design speed should be a logical one with respect to the ...
The following section pertains to only North American highway LOS standards as in the Highway Capacity Manual (HCM) and AASHTO Geometric Design of Highways and Streets ("Green Book"), using letters A through F, with A being the best and F being the worst, similar to academic grading. A: free flow. Traffic flows at or above the posted speed ...
AASHO Road Test was a set of experiments carried out by the AASHTO from 1956 to 1961. [4] Unlike the PSR, which was a ride quality rating that required a panel of observers to ride in a car over the pavement of interest, the PSI does not require a panel of experts. Therefore, it was a more practical approach for large-scale pavement networks.
The Manual on Uniform Traffic Control Devices for Streets and Highways (usually referred to as the Manual on Uniform Traffic Control Devices, abbreviated MUTCD) is a document issued by the Federal Highway Administration (FHWA) of the United States Department of Transportation (USDOT) to specify the standards by which traffic signs, road surface markings, and signals are designed, installed ...
Typically on straight road sections, the drainage gradient is at least 1–3% due to the normal cross slope of 1–3%. In curved sections the drainage gradient is higher, and may often reach 5–12% due to superelevated CS that may reach 5–8% in areas with icy roads and up to 12% in areas without icy roads.