Intersections

All at-grade intersections of public highways and private driveways shall be eliminated, or the connecting road terminated, rerouted, or intercepted by frontage roads, except as otherwise provided under Control of Access.

Design Speed

The design speed of all highways on the system shall be at least 70, 60, and 50 miles per hour for flat, rolling, and mountainous topography, respectively, and depending upon the nature of terrain and development. The design speed in urban areas should be at least 50 miles per hour.

Curvature, Superelevation, and Sight Distance

These elements and allied features, such as transition curves, should be correlated with the design speed in accordance with the Policy on Geometric Design of Rural Highways of the American Association of State Highway Officials.

On 2-lane highways, sections with sufficient sight distance for safe passing should be frequent enough and the total length of such sections be a sufficient percentage of the highway length to accommodate the DHV. Where it is not feasible to provide enough passing opportunities, a divided highway should be provided instead.

Gradients

For design speeds of 70, 60, and 50 miles per hour, gradients generally shall be not steeper than 3, 4, and 5 percent, respectively. Gradients 2 percent steeper may be provided in rugged terrain.

Width and Number of Lanes

Traffic lanes shall not be less than 12 feet wide.

Where the DHV (1975) exceeds 700 or exceeds a lower 2-lane design capacity applicable for the conditions on a particular section, the highway shall be a divided highway. For lower volumes, the highway shall be a 2-lane highway so designed and located on the right-of-way that an additional 2-lane pavement can be added in the future to form a divided highway.

Efficiency and capacity of 2-lane highways may be increased by providing added climbing lanes on upgrades where critical lengths of grade are exceeded or by providing more frequent and longer sections safe for passing.

Medians

Medians in rural areas in flat and rolling topography shall be at least 36 feet wide. Medians in urban and mountainous areas shall be at least 16 feet wide. Narrower medians may be provided in urban areas of high right-of-way cost, on long and costly bridges, and in rugged mountainous terrain, but no median shall be less than 4 feet wide.

Curbs or other devices may be used where necessary to prevent traffic from crossing the median..

Where continuous barrier curbs are used on narrow medians, such curbs shall be offset at least 1 foot from the edge of the through-traffic lane. Where vertical elements more than 12 inches high, other than abutments, piers, or walls, are located in a median, there shall be a lateral clearance of at least 32 feet from the edge of the through-traffic lane to the face of such element. Shoulders

Shoulders usable by all classes of vehicles in all weather shall be provided on the right of traffic. The usable width of shoulder shall be not less than 10 feet. In mountainous terrain involving high cost for additional width, the usable width of shoulder may be less but at least 6 feet. Usable width of shoulder is measured from edge of through-traffic lane to intersection of shoulder and fill or ditch slope except where such slope is steeper than 4:1 where it is measured to beginning of rounding.

Slopes

Side slopes should be 4:1 or flatter where feasible and not steeper than 2:1 except in rock excavation or other special conditions.

Right-of-Way

Fixed minimum widths of right-of-way are not given because wide widths are desirable, conditions may make narrow widths necessary, and right-of-way need not be of constant width. The following minimum widths are given as guides.

In rural areas right-of-way widths should be not less than the following, plus additional widths needed for heavy cuts and fills:

In urban areas right-of-way widths shall be not less than that required for the necessary cross-section elements, including median, pavements, shoulders, outer separations, ramps, frontage roads, slopes, walls, border areas, and other requisite appurtenances.

Culverts

All culverts shall be of sufficient length to accommodate the pavements, median, and shoulders.

Bridges and Other Structures

The following standards apply to Interstate highway bridges, overpasses, and underpasses. Standards for crossroad overpasses and underpasses are to be those for the crossroad.

Bridges and overpasses, preferably of deck construction, should be located to fit the overall alinement and profile of the highway.

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The clear height of structures shall be not less than 16 feet over the entire roadway width, including the usable width of shoulders. Allowance should be made for any contemplated resurfacing.

The width of all bridges, including grade-separation structures, of a length of 150 feet or less between abutments or end supporting piers shall equal the full roadway width on the approaches, including the usable width of shoulders.

Barrier curbs on bridges longer than 150 feet between abutments or end supporting piers, and curbs on approach highways, if used, shall be offset at least 2 feet. Offsets to face of parapet or rail shall be at least 311⁄2 feet measured from edge of throughtraffic lane, and apply on right and left.

The lateral clearance from the edge of through-traffic lanes to the face of walls or abutments and piers at underpasses shall be the usable shoulder width but not less than 8 feet on the right and 412 feet on the left.

A safety walk shall be provided in tunnels and on long-span structures on which the full approach roadway width, including shoulders, is not continued.

U.S. Department of Commerce, Bureau of Public Roads (Reprint from Federal Register 23 F.R. 8793, November 13, 1958, as amended, 25 F.R. 218, January 12, 1960-25 F.R. 2575, March 26, 1960)

Code of Federal Regulations, Title 23-Highways CHAPTER I-BUREAU OF PUBLIC ROADS, DEPARTMENT OF COMMERCE

Part 20-National Standards for Regulation by States of Outdoor Advertising Signs, Ďisplays and Devices Adjacent to the National System of Interstate and Defense Highways

20.10 State regulations.

AUTHORITY: §§ 20.1 to 20.10 issued under sec. 131, 72 Stat. 904; 23 U.S.C..

131.

§ 20.1 Purpose

(a) In Title 23, United States Code, section 131, hereinafter called the "act", the Congress has declared that :

(1) To promote the safety, convenience, and enjoyment of public travel and the free flow of interstate commerce and to

3 Revision from 14 to 16 feet, effective January 27, 1960.

protect the public investment in the National System of Interstate and Defense Highways, hereinafter called the "Interstate System", it is in the public interest to encourage and assist the States to control the use of and to improve areas adjacent to such system by controlling the erection and maintenance of outdoor advertising signs, displays and devices adjacent to that system. (2) It is a national policy that the erection and maintenance of outdoor advertising signs, displays, or devices within six hundred and sixty feet of the edge of the right-of-way and visible from the main-traveled way of all portions of the Interstate System constructed upon any part of right-of-way, the entire width of which is acquired subsequent to July 1, 1956, should be regulated, consistent with national standards to be prepared and promulgated by the Secretary of Commerce.

(b) The standards in this part are hereby promulgated as provided in the act.

§ 20.2 Definitions

The following terms when used in the standards in this part have the following meanings:

(a) "Acquired for right-of-way" means acquired for right-ofway for any public road by the Federal Government, a State, or a county, city or other political subdivision of a State, by donation, dedication, purchase, condemnation, use, or otherwise. The date of acquisition shall be the date upon which title (whether fee title or a lesser interest) vested in the public for right-of-way purposes under applicable Federal or State law.

(b) "Centerline of the highway" means a line equidistant from the edges of the median separating the main-traveled ways of a divided Interstate highway, or the centerline of the main-traveled way of a non-divided Interstate highway.

(c) "Controlled portion of the Interstate System" means any portion which

(1) Is constructed upon any part of right-of-way, the entire width of which is acquired for right-of-way subsequent to July 1, 1956 (a portion shall be deemed so constructed if, within such portion, no line normal or perpendicular to the centerline of the highway and extending to both edges of the right-of-way will intersect any right-of-way acquired for right-of-way on or before July 1, 1956);

(2) Lies within a State, the highway department of which has entered into an agreement with the Secretary of Commerce as provided in the act; and

(3) Is not excluded under the terms of the act which provide that agreements entered into between the Secretary of Commerce and the State highway department shall not apply to those segments of the Interstate System which traverse commercial or industrial zones within the boundaries of incorporated municipalities, as such boundaries existed on September 21, 1959, wherein the use of real property adjacent to the Interstate System is subject to municipal regulation or control, or which traverse other areas where

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the land use as of September 21, 1959, was clearly established by State law as industrial or commercial.1

(d) "Entrance roadway" means any public road or turning roadway, including acceleration lanes, by which traffic may enter the main-traveled way of an Interstate highway from the general road system within a State, irrespective of whether traffic may also leave the main-traveled way by such road or turning roadway.

(e) "Erect" means to construct, build, raise, assemble, place, affix, attach, create, paint, draw, or in any way bring into being or establish.

(f) "Exit roadway" means any public road or turning roadway, including deceleration lanes, by which traffic may leave the main-traveled way of an Interstate highway to reach the general road system within a State, irrespective of whether traffic may also enter the main-traveled way by such road or turning roadway. (g) "Informational site" means an area or site established and maintained within or adjacent to the right-of-way of a highway on the Interstate System by or under the supervision or control of a State highway department, wherein panels for the display of advertising and informational signs may be erected and maintained.

(h) "Legible" means capable of being read without visual aid by a person of normal visual acuity.

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"Maintain" means to allow to exist.

(j) "Main-traveled way" means the traveled way of an Interstate highway on which through traffic is carried. In the case of a divided highway, the traveled way of each of the separated roadways for traffic in opposite directions is a main-traveled way. It does not include such facilities as frontage roads, turning roadways, or parking areas.

(k) "Protected areas" means all areas inside the boundaries of a State which are adjacent to and within six hundred and sixty feet of the edge of the right-of-way of all controlled portions of the Interstate System within that State. Where a controlled portion of the Interstate System terminates at a State boundary which is not perpendicular or normal to the centerline of the highway, "protected areas" also means all areas inside the boundary of such State which are within six hundred and sixty feet of the edge of the right-of-way of the Interstate highway in the adjoining State.

(1) ❝Scenic area" means any public park or area of particular scenic beauty or historical significance designated by or pursuant to State law as a scenic area.

(m) "Sign" means any outdoor sign, display, device, figure, painting, drawing, message, placard, poster, billboard, or other thing which is designed, intended, or used to advertise or inform, any part of the advertising or informative contents of which is visible from any place on the main-traveled way of a controlled portion of the Interstate System.

1 Effective date January 12, 1960.