The previous edition, known as the Green Book, was adopted by the Federal Highway Administration on February 12, Our office memorandum dated February 15, , described how the Green Book should be applied as the design standard for all projects on the National Highway System NHS. The major change in the Green Book is revision of the superelevation section. The superelevation revisions and other minor changes are described in Attachment 1.
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The previous edition, known as the Green Book, was adopted by the Federal Highway Administration on February 12, Our office memorandum dated February 15, , described how the Green Book should be applied as the design standard for all projects on the National Highway System NHS.
The major change in the Green Book is revision of the superelevation section. The superelevation revisions and other minor changes are described in Attachment 1. It has been determined that the Green Book is in substantial conformance with the criteria in the adopted Green Book.
States are therefore allowed to use either the or Green Book as the design standard for projects on the NHS. At a later date, one copy of the Green Book will be furnished to each field office. Attachment Changes in Green Book as compared with Green Book The superelevation section has been revised as follows: The topics in the section have been reworded and rearranged The superelevation tables have been reformatted.
In the Green Book the superelevation tables were formatted with radius in the left column and design speed across the top, enabling the user with these two pieces of information to find the recommended superelevation value in the body of the table. In the Green Book the superelevation tables are formatted with superelevation in the left column and design speed across the top, enabling the user to enter from the top with design speed, proceed down a column in the body of the table to curve radius, and find a recommended superelevation value in the left column.
The length of superelevation runoff has been moved from the superelevation table to a separate table in the discussion of transition design controls. For low speed urban streets, use of superelevation is optional, as it was in the Green Book. Where superelevation is used, the Green Book presents the superelevation rates in a new table and revised graph.
The change in superelevation rates is similar to those for rural facilities The terminology for M, middle ordinate of a horizontal curve, has been changed to HSO, horizontal sightline offset, to avoid conflict with a surveying term using M.
This is a straight substitution of terms, no other changes were made in the text. The technical corrections noted in the first and second printings of the Green Book have been incorporated in the Green Book.
American Association of State Highway and Transportation Officials
The name change reflects a broadened scope to cover all modes of transportation, although most of its activities are still specific to highways. This book covers the functional design of roads and highways including such things as the layout of intersections, horizontal curves and vertical curves. One such project is the AASHTO Road Test , which is a primary source of data used when considering transport policies and the structural design of roads. Accreditation is often required to submit test results to state DOTs. For example, a contract for the construction of a highway bridge may require a minimum compressive strength for the concrete used. The laboratory performing T 22 will be required to be accredited in that test.