The American Association of State Highway and Transportation Officials (AASHTO) defines standards for Interstate Highways in their publication A Policy on Design Standards - Interstate System. For a highway to be an Interstate, it must be built to these standards or obtain a waiver from the Federal Highway Administration. AASHTO, the American Association of State Highway and Transportation Officials, is a standards setting body which publishes specifications, test protocols and guidelines which are used in highway design and construction throughout the United States. ... A typical rural stretch of Interstate highway, with two lanes in each direction separated by a large grassy median, and with cross-traffic limited to overpasses and underpasses. ... A waiver is the voluntary relinquishment or surrender of some right or privilege. ... The Federal Highway Administration (FHWA) is a division of the U.S. Department of Transportation that specializes in automobile transportation. ...

These standards are (as of August 2003):

• All access is to be controlled with interchanges and grade separations (including railroad crossings). See List of gaps in Interstate Highways for the few cases that violate this rule. Interchanges should provide full access; ramps are to be designed with the appropriate standards in mind. Minimum interchange spacing should be 1.5 km (1 mi) in urban areas and 5 km (3 mi) in rural areas; collector-distributor roads or other configurations that reduce weaving can be used in urban areas to shorten this distance.
  • Access control (from adjacent properties) should extend at least 30 m (100 ft) in urban areas and 90 m (300 ft) in rural areas in each direction along the crossroad from the ramps.
• Minimum design speed of 70 mph (110 km/h) in rural areas, with 60 mph (100 km/h) acceptable in rolling terrain, and as low as 50 mph (80 km/h) allowed in mountainous and urban areas.
  • Sight distance, curvature and superelevation according to the current edition of AASHTO's A Policy on Geometric Design of Highways and Streets for the design speed.
• Maximum grade determined by a table, with up to 6% allowed in mountainous areas and hilly urban areas.
• At least two lanes in each direction, and more if necessary for an acceptable level of service in the design year, 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.
• Minimum lane width of 3.6 m (12 ft).
• Minimum outside paved shoulder width of 3.0 m (10 ft) and inside shoulder width of 1.2 m (4 ft). With three or more lanes in each direction, the inside paved shoulder should be at least 3.0 m (10 ft) wide. If truck traffic is over 250 Directional Design Hour Volume, shoulders at least 3.6 m (12 ft) wide should be considered. In mountainous terrain, 2.4 m (8 ft) outside and 1.2 m (4 ft) inside shoulders are acceptable, except when there are at least four lanes in each direction, in which case the inside shoulders should also be 2.4 m (8 ft) wide.
• Pavement cross slope of at least 1.5% and preferably 2% to ensure proper drainage on straight sections. This can be increased to 2.5% in areas of heavy rainfall. Shoulder cross slope should be between 2% and 6% but not less than the main lanes.
• Land slopes within the clear zone should be at most 4:1 and preferably 6:1 or flatter. Roadside barriers should be used for slopes of 3:1 or steeper, in accordance with the current edition of AASHTO's Roadside Design Guide.
• Minimum median width of 11 m (36 ft) in rural areas, and 3.0 m (10 ft) in urban or mountainous areas. To prevent median-crossing accidents, guardrail should be installed in medians in accordance with the current edition of AASHTO's Roadside Design Guide, based on traffic, median width and crash history. When possible, median openings between parallel bridges less than 9.0 m (30 ft) in width should be decked over; otherwise barriers or guardrails should be installed to keep vehicles out of the hole.
• No fixed objects should be in the clear recovery area, determined by the design speed in accordance with the current edition of AASHTO's Roadside Design Guide. When this is not possible, breakaway supports or barriers guarding the objects shall be used.
• Vertical curbs are prohibited. Sloping curbs are to be at the edge of the paved shoulder, with a maximum height of 100 mm (4 in). The combination of curbs and guardrail is discouraged; in this case the guardrail should be closer to the road than the curb.
• Minimum vertical clearance under overhead structures (including over the paved shoulders) of 4.9 m (16 ft) in rural areas and 4.3 m (14 ft) in urban areas, with allowances for extra layers of pavement. Through urban areas at least one routing should have 4.9 m (16 ft) clearances. Sign supports and pedestrian overpasses must be at least 5.1 m (17 ft) above the road, except on urban routes with lesser clearance, where they should be at least .3 m (1 ft) higher than other objects. Vertical clearance on through truss bridges is to be at least 5.1 m (17 ft).
• Horizontal clearance under or along a bridge shall be the full paved width of the rest of the road. Bridges longer than 60 m (200 ft) can be narrower, with a minimum of 1.2 m (4 ft) on both sides of the travel lanes.
• New bridges are to have at least MS 18 (HS-20) structural capacity. Weaker bridges that can continue to serve the route for 20 more years are allowed to remain.
  • Additionally, existing bridges can remain if they have at least 3.6 m (12 ft) lanes with 3.0 m (10 ft) outside and 1.1 m (3.5 ft) inside shoulders. Long bridges are to have at least 1.1 m (3.5 ft) on each side of the travel lanes; bridge railing should be upgraded to current standards if necessary.
• Tunnels should in theory be equivalent to long overcrossings, but because of cost the standards can be reduced. Vertical clearance is the same as under bridges, including the provision for an alternate routing. Width should be at least 13.1 m (44 ft), which consists of two 3.6 m (12 ft) lanes, 3.0 m (10 ft) outside and 1.5 m (5 ft) inside shoulders, and .7 m (2.5 ft) safety walkways on each side. If necessary to meet the dimensions of the approach, this can be shifted left or right. A reduced width is acceptable due to high costs. In this case, the minimum width is 9.0 m (30 ft), with at least .6 m (2 ft) more than the approach for the sum of the shoulder widths, but at least 7.2 m (24 ft) total, and at least .5 m (1.5 ft) on each side for a safety walkway. If there is no safety walkway, a 1.0 m (3 ft) offset with a "safety shape" in the wall is acceptable.

The standards have been changed over the years, resulting in many older Interstates not being built to the current standards. Other roads were grandfathered into the system, and yet others are not built to standards because to do so would be too costly or environmentally unsound. A typical rural freeway (Interstate 5 in the Central Valley of California). ... In the field of road transport, a road junction is a place where two or more roads either meet or cross. ... Grade separation refers to separating two item that cross each other by placing them on different levels, or at different heights, to each other. ... This is the top-level page of WikiProject trains Rail tracks Rail transport refers to the land transport of passengers and goods along railways or railroads. ... For the most part, the United States Interstate Highway System is a connected system, with most roads completed. ... For the landform that extends above the surrounding terrain and that is smaller than a mountain, see the article on mountain. ... Mount Cook, a mountain in New Zealand A mountain is a landform that extends above the surrounding terrain in a limited area. ... The term urban means cities and towns as distinct from rural areas. ... Curvature is the amount by which a geometric object deviates from being flat. ... This page is a candidate to be moved to Wiktionary. ... In topography, the slope of a hill, mountain, road or anything else inclined, is more often referred to as its grade (or, sometimes in the US and usually in the UK, gradient). ... The word lane has two meanings: A narrow road, usually lacking a shoulder or a median. ... Level of service is a measure by which transportation planners reckon the quality of service on transportation devices, or transportation infrastructure, generally linked to transportation time (the shorter, the better) and thus to speed. ... This page is a candidate to be moved to Wiktionary. ... A hard shoulder or simply shoulder is a reserved area alongside the verge of a road or motorway. ... Drainage is the natural or artifical removal of surface and sub-surface water from a given area. ... In meteorology, precipitation is any kind of water that falls from the sky as part of the weather. ... This page is a candidate to be moved to Wiktionary. ... On an expressway, motorway, or autobahn, the median (North American English) or central reservation (British English) is the strip of grass or the wall which separates opposing lanes of traffic. ... This page is a candidate to be moved to Wiktionary. ... This page is a candidate to be moved to Wiktionary. ... Curb may refer to : Curb Records the side of a road, see curb extension a shortened name for the HBO comedy show Curb Your Enthusiasm Curb, Nickelbacks first full-length album see also kerb A curb bit is a type of leverage bit used on horses. ... The clearance, also renal clearance or renal plasma clearance (when referring to the function of the kidney), of a substance is the inverse of the time constant that describes its removal rate from the body divided by the total body water. ... This article is about the American English usage of pavement as the durable surfacing of roads and walkways. ... A disused railway tunnel now converted to pedestrian and bicycle use, near Houyet, Belgium A tunnel is an underground passage. ... In the United States, a grandfather clause is an exception which allows something pre-existing to remain as it is, despite a change to the contrary in the rules applied to newer situations. ...

edit Primary Interstate Highways
4	5	8	10	12	15	16	17
19	20	22	24	25	26	27	29
30	35	37	39	40	43	44	45
49	55	57	59	64	65	66	68
69	70	71	72	73	74	75	76 (W)
76 (E)	77	78	79	80	81	82	83
84 (W)	84 (E)	85	86 (W)	86 (E)	87	88 (W)	88 (E)
89	90	91	93	94	95	96	97
99	238	H-1	H-2	H-3
Unsigned Interstate Highways
A-1	A-2	A-3	A-4	PRI-1	PRI-2	PRI-3
Lists Two-digit Interstates - Three-digit Interstates Gaps in Interstates - Intrastate Interstates Interstate standards - Proposed Interstates

A typical rural stretch of Interstate Highway, with two lanes in each direction separated by a large grassy median, and with cross-traffic limited to overpasses and underpasses. ... Download high resolution version (768x768, 17 KB) Wikipedia does not have an article with this exact name. ... An old shield in Orlando, Florida Interstate 4 is an intrastate Interstate Highway located entirely within the state of Florida, United States. ... Interstate 5, or I-5, is an interstate highway along the west coast of the United States. ... Interstate 8 is an interstate highway in the southwestern United States. ... Interstate 10, or I-10, is the southernmost east-west, coast-to-coast interstate highway in the United States. ... Interstate 12 is an intrastate interstate highway located entirely within the state of Louisiana, United States. ... Interstate 15, or I-15, is a north-south interstate highway in the western United States, traveling through the states of Montana, Idaho, Utah, Arizona, Nevada, and California. ... Interstate 16 (Georgia State Route 404) is an intrastate interstate highway located entirely within the state of Georgia, United States. ... Interstate 17 is an intrastate interstate highway located entirely within the state of Arizona, United States. ... Interstate 19 is an intrastate interstate highway located entirely within the state of Arizona, United States. ... Interstate 20 is an interstate highway in the southeastern United States. ... Previously known as Corridor X (one of the Appalachian Regional Corridors), Interstate 22, when completed, will follow the U.S. Highway 78 corridor along a 176 mile (283 km) route from Memphis, Tennessee to Birmingham, Alabama. ... Interstate 24 is an interstate highway in the eastern United States. ... Interstate 25 is an interstate highway in the western United States. ... Interstate 26 is an interstate highway in the southeastern United States. ... Interstate 27 is an intrastate interstate highway located entirely within the state of Texas in the United States. ... Interstate 29 is an interstate highway in the Midwestern United States. ... Interstate 30 is an interstate highway in the southern United States. ... Interstate 35 (I-35) is an interstate highway running north-south in the central United States. ... Interstate 37 is an intrastate interstate highway located within the state of Texas, United States. ... Interstate 39 is an interstate highway in the midwestern United States. ... Interstate 40 is a major west-east interstate highway in the United States. ... Interstate 43 is an intrastate interstate highway located entirely within the state of Wisconsin, United States. ... Interstate 44 is an interstate highway in the central United States. ... Interstate 45 is an intrastate interstate highway located entirely within the state of Texas, United States. ... Interstate 49 is an intrastate interstate highway located entirely within the state of Louisiana, United States. ... Interstate 55 is an interstate highway in the central United States. ... Interstate 57 is an interstate highway in the midwestern United States. ... Interstate 59 is an interstate highway in the southern United States. ... Interstate 64 is an Interstate Highway in the eastern United States. ... Interstate 65 is an Interstate Highway in the United States. ... Interstate 66 is an interstate highway in the eastern United States. ... Interstate 68 is an interstate highway in the United States. ... It has been suggested that Temporary Interstate 69 (between Lansing and Flint) be merged into this article or section. ... I-70 looking westbound near Mile 326, Wabaunsee County, Kansas Interstate 70 is a long interstate highway in the United States. ... Interstate 71 is an Interstate Highway in the midwestern United States. ... Interstate 72 is an interstate highway in the midwestern United States. ... Interstate 73 is an intrastate interstate highway located entirely within the state of North Carolina. ... Interstate 74 is an interstate highway in the midwestern United States. ... Interstate 75 is an interstate highway in the midwest and southeastern United States. ... Interstate 76 runs from Interstate 70 in Denver, Colorado to an intersection with Interstate 80 near Big Springs, Nebraska. ... Interstate 76 runs from an intersection with Interstate 71 between Seville, Ohio and Westfield Center, Ohio, about 20 miles (32 km) west of Akron, to an intersection with I-295 near Camden, New Jersey. ... Interstate 77 is an interstate highway in the eastern United States. ... Interstate 78 is an interstate highway in the eastern United States. ... Interstate 79 is an interstate highway in the eastern United States. ... Interstate 80 as seen from an overpass in Davis, California Interstate 80 is the second-longest interstate highway in the United States. ... I-81 looking southbound near mile 245, Harrisonburg, Virginia. ... Interstate 82 is an interstate highway in the northwestern United States. ... Interstate 83 is an interstate highway in the eastern United States. ... Columbia River Gorge and I-84 as seen from Crown Point, Oregon Interstate 84 runs from an intersection with Interstate 5 at Portland, Oregon to an intersection with Interstate 80 at Echo, Utah—roughly the same route as the Oregon Trail. ... Interstate 84 runs from Scranton, Pennsylvania at an intersection with Interstate 81 to Sturbridge, Massachusetts at an intersection with the Massachusetts Turnpike (Interstate 90). ... Interstate 85 is an interstate highway in the southeastern United States. ... Interstate 86 is an intrastate Interstate Highway, located entirely within the state of Idaho. ... Interstate 86 runs from an intersection with Interstate 90 in Erie, Pennsylvania to Elmira, New York at the border between Chemung County, New York and Steuben County, New York along what was formerly New York State Highway 17. ... Interstate 87 is a 346 mile (558 km) intrastate interstate highway located entirely within the state of New York. ... Interstate 88 is entirely within the state of Illinois. ... Interstate 88 is entirely within the state of New York. ... Interstate 89 is an interstate highway in the New England portion of the United States. ... Interstate 90 is the longest interstate highway in the United States at over 3,100 miles. ... Interstate 91 is an interstate highway in the New England section of the United States. ... Interstate 93 is an interstate highway in the New England section of the United States. ... I-94 redirects here. ... Interstate 95 or (I-95) is an interstate highway that runs 1907 miles (3070 kilometers) north-south along the east coast of the United States. ... Interstate 96 is an intrastate Interstate highway entirely within the state of Michigan. ... Interstate 97 is an intrastate Interstate highway located entirely within Anne Arundel County, Maryland, United States. ... Interstate 99 is a part of the US Interstate highway system. ... JUNCTION MILE POST {{{junction}}} Legend < Route 238 Route 239 > California State Highways Current - Unconstructed - Deleted - Scenic Interstate 238 is a short (2. ... Interstate H-1 is an intrastate interstate highway in Hawaii, United States, on the island of Oahu. ... Interstate H-2 (also known as the Veterans Memorial Freeway) is an intrastate interstate highway located on the island of Oahu in Hawaii. ... Interstate H-3 in Halawa Valley looking towards the Koolau crest Interstate H-3 (also known as the John A. Burns Freeway) is an intrastate interstate highway located on the island of O‘ahu in the state of Hawai‘i, United States. ... There are four officially designated Interstate Highways in Alaska. ... There are four officially designated Interstate Highways in Alaska. ... There are four officially designated Interstate Highways in Alaska. ... There are four officially designated Interstate Highways in Alaska. ... There are three officially designated Interstate Highways in Puerto Rico. ... There are three officially designated Interstate Highways in Puerto Rico. ... There are three officially designated Interstate Highways in Puerto Rico. ... Primary interstates are the major interstate highways of the United States and are assigned a one or two-digit route number. ... This is a list of 3-digit Interstate Highway route designations in the United States. ... For the most part, the United States Interstate Highway System is a connected system, with most roads completed. ... The following two-digit United States Interstate Highways do not cross state lines. ... The Interstate Highway system is still being expanded. ...

External links

• AASHTO Bookstore - A Policy on Design Standards - Interstate System

References

• A Policy on Design Standards - Interstate System (July 1991-August 2003)
• "Interstate standards", John Lansford, misc.transport.road November 2, 1999