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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.
The primary US guidance is found in A Policy on Geometric Design of Highways and Streets published by the American Association of State Highway and Transportation Officials (AASHTO). [2] Other standards include the Australian Guide to Road Design Archived 2011-11-09 at the Wayback Machine, and the British Design Manual for Roads.
Minimum number of lanes: There are to be at least two lanes in each direction, unless more are necessary for an acceptable level of service, according to the current edition of AASHTO's A Policy on Geometric Design of Highways and Streets. Climbing lanes and emergency escape ramps should be provided where appropriate.
A Policy on Geometric Design of Highways and Streets, or The Green Book, a publication by the American Association of State Highway and Transportation Officials on roadway and street engineering design; Green Books, the multi-volume Official History of the United States Army in World War II
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 ...
Highway engineering (also known as roadway engineering and street engineering) is a professional engineering discipline branching from the civil engineering subdiscipline of transportation engineering that involves the planning, design, construction, operation, and maintenance of roads, highways, streets, bridges, and tunnels to ensure safe and effective transportation of people and goods.
The operating speed of a road is the speed at which motor vehicles generally operate on that road.. The precise definition of "operating speed", however, is open to debate. Some sources, such as the AASHTO, have changed their definitions recently to match the common use of the wo
The design speed is a tool used to determine geometric features of a new road or street during road design.Contrary to the word's implication, the design speed of the road or street is not necessarily its vehicle speed limit or maximum safe speed; that can be higher or lower.