The Intermodal Surface Transportation Efficiency Act of 1991 (ISTEA, ) is a United States federal law that posed a major change to transportation planning and policy, as the first U.S. federal legislation on the subject in the post-Interstate Highway System era.

The act was signed into law on December 18, 1991, by President George H. W. Bush and codified as and .

Objective The act presented an overall intermodal approach to highway and transit funding with collaborative planning requirements, giving significant additional powers to metropolitan planning organizations (MPOs).

ISTEA also provided funds for the conversion of dormant railroad corridors into rail trails; the first rail trail to be funded was the Cedar Lake Regional Rail Trail, in Minneapolis, Minnesota.

The bill was preceded by the Surface Transportation and Uniform Relocation Assistance Act in 1987 and followed by the Transportation Equity Act for the 21st Century (TEA-21) in 1998, the Safe, Accountable, Flexible, Efficient Transportation Equity Act: A Legacy for Users (SAFETEA-LU) in 2005, the Moving Ahead for Progress in the 21st Century Act (MAP-21) in 2012, the Fixing America's Surface Transportation Act (FAST) in 2015, and the Infrastructure Investment and Jobs Act in 2021.

High priority corridors Section 1105 of the act also defines a number of High Priority Corridors, to be part of the National Highway System. After various amendments in subsequent transportation bills and other legislation, this is a list of the corridors:

+ List of High Priority Corridors Corridor # Name Location Notes1North-South CorridorKansas City, Missouri to Shreveport, LouisianaInterstate 492Avenue of the Saints CorridorSt. Louis, Missouri to St. Paul, Minnesota3East-West Transamerica CorridorHampton Roads, Virginia to southern KansasInterstate 66 (Kansas–Kentucky)Project officially cancelled on August 6, 20154Hoosier Heartland Industrial CorridorLafayette, Indiana to Toledo, Ohio5I-73/74 North-South CorridorMyrtle Beach, South Carolina to Cincinnati, Ohio, Detroit, Michigan and Sault Ste. Marie, Michigan6United States Route 80 CorridorMeridian, Mississippi to Savannah, Georgia7East-West CorridorMemphis, Tennessee to Atlanta, Georgia and Chattanooga, TennesseePartially complete. Interstate 565 from Decatur, Alabama to Huntsville, Alabama.8Highway 412 East-West CorridorTulsa, Oklahoma to Nashville, Tennessee9United States Route 220 and the Appalachian Thruway CorridorBedford, Pennsylvania to Corning, New YorkInterstate 9910Appalachian Regional Corridor XFulton, Mississippi to Birmingham, AlabamaSee corridor 4511Appalachian Regional Corridor VFrom Interstate 55 in northern Mississippi in the west to Interstate 24 in East TennesseeRoute is from Batesville, Mississippi, and via Tupelo, Mississippi, Russellville, Alabama, and Huntsville, Alabama, ending just west of Chattanooga, Tennessee See also corridor 42.12United States Route 25E CorridorCorbin, Kentucky to Morristown, Tennessee13Raleigh-Norfolk CorridorRaleigh, North Carolina to Norfolk, VirginiaInterstate 87 (North Carolina–Virginia)14Heartland ExpresswayDenver, Colorado to Rapid City, South Dakota15Urban Highway CorridorM-59 in Michigan16Economic Lifeline CorridorI-15 and I-40 in California, Arizona, and Nevada17Route 29 CorridorGreensboro, North Carolina to Washington, D.C.18Port Huron, Michigan to Chicago, Illinois, Corpus Christi, Texas and Victoria, TexasInterstate 69 (see Corridor 20)19United States Route 395 CorridorCanada–US border to Reno, Nevada20United States Route 59 CorridorLaredo, Texas to Texarkana, TexasInterstate 69 (see Corridor 18)21United States Route 219 CorridorBuffalo, New York to Interstate 8022Alameda Transportation CorridorPorts of Los Angeles and Long Beach to Interstate 10(See Corridor 34)23Interstate Route 35 CorridorLaredo, Texas to Duluth, Minnesota and the Canada–US border (via Interstate 29)24Dalton HighwayDeadhorse, Alaska to Fairbanks, Alaska25State Route 168 (South Battlefield Boulevard)Great Bridge, Virginia Bypass to the North Carolina state line26CANAMEX CorridorNogales, Arizona to the Canada–US borderInterstate 11 and Interstate 1527Camino Real CorridorEl Paso, Texas to the Canada–US border28Birmingham Northern BeltlineBirmingham, AlabamaAppalachian Highway Development System Corridor X-129Coalfields ExpresswayBeckley, West Virginia to Pound, Virginia30Interstate Route 5California, Oregon and Washington31Mon–Fayette Expressway and Southern BeltwayPennsylvania and West Virginia32Wisconsin Development CorridorDubuque, Iowa to Eau Claire, WisconsinConsists of three different corridors in the state of Wisconsin33Capital Gateway CorridorWashington, D.C. to the Baltimore-Washington Parkway in MarylandU.S. Route 5034Alameda Corridor-East and Southwest PassageEast Los Angeles, California to Barstow, California and Coachella, California, and San Bernardino, California to Arizona(See Corridor 22)35Everett-Tacoma FAST CorridorEverett, Washington to Tacoma, Washington36NY-17Harriman, New York to I-90 in PennsylvaniaISTEA mandates that route be Interstate 8637United States Route 90Lafayette, Louisiana to New Orleans, LouisianaInterstate 4938Ports-to-Plains CorridorLaredo, Texas to Denver, ColoradoInterstate 27 (Lubbock, Texas to Amarillo, Texas)39United States Route 63Marked Tree, Arkansas to Interstate 55Interstate 55540Greensboro CorridorDanville, Virginia to Greensboro, North CarolinaInterstate 78541Falls-to-Falls CorridorInternational Falls, Minnesota to Chippewa Falls, Wisconsin42Batesville to Fulton, Mississippiformed from portions of ADHS corridors V and X; law designates highway as a future Interstate highway (route number not specified in law)43United States Route 95 CorridorEastport, Idaho to Oregon44Louisiana Highway 1 CorridorGrand Isle, Louisiana to U.S. Route 9045United States Route 78 CorridorMemphis, Tennessee to Birmingham, AlabamaInterstate 2246Interstate Route 710Long Beach, California to California State Route 6047Interstate Route 87Quebec to New York City48Route 50 High Plains CorridorNewton, Kansas to Pueblo, Colorado49Atlantic Commerce CorridorJacksonville, Florida to Miami, Florida50East-West CorridorWatertown, New York to Calais, Maine51SPIRIT CorridorEl Paso, Texas to Wichita, Kansas52Swifton, Arkansas to Jonesboro, Arkansas53United States Highway Route 6Interstate 70 to Interstate 1554California Farm-to-Market Corridorsouth of Bakersfield, California to Sacramento, CaliforniaCalifornia State Route 9955Dallas, Texas to Memphis, Tennessee56La Entrada al Pacifico CorridorLamesa, Texas to Presidio, Texas57United States Route 41 corridorMilwaukee, Wisconsin to Green Bay, WisconsinInterstate 4158Theodore Roosevelt ExpresswayRapid City, South Dakota to Raymond, Montana59Central North American Trade Corridorborder between North Dakota and South Dakota to the Canada–US border60Providence Beltline CorridorHope Valley, Rhode Island to Massachusetts61various corridors in Missouri62Georgia Developmental Highway System Corridorsvarious corridors in Georgia63Liberty Corridorvarious corridors in northern New Jersey64various corridors in southern New Jersey65Interstate Route 95 CorridorConnecticut66Interstate Route 91 CorridorConnecticut67Fairbanks-Yukon International CorridorCanada–US border to Fairbanks, Alaska68Intermountain West Corridor and Washoe County CorridorLas Vegas, Nevada to Reno, NevadaInterstate 11 and Interstate 8069Cross Valley ConnectorInterstate 5 to State Route 14, Santa Clarita Valley, California70Economic Lifeline corridorI-15, I-40 and other roads in California, Arizona and Nevada71High Desert CorridorLos Angeles, California to Las Vegas, NevadaBrightline West via Interstate 1572North-South corridorKansas City, Missouri to Shreveport, LouisianaInterstate 4973Louisiana Highway corridorGrand Isle, Louisiana to U.S. Route 9074Lafayette, Louisiana to New Orleans, LouisianaInterstate 4975Louisiana 28 corridorFort Polk, Louisiana to Alexandria, Louisiana76Toledo, Ohio to Cincinnati, Ohio77Indiana to Toledo, Ohio78Cincinnati, Ohio to Cleveland, Ohio79Interstate Route 376Monroeville, Pennsylvania to Sharon, Pennsylvania80Intercounty ConnectorInterstate 270 to Interstate 95/U.S. Route 1 in Maryland81Interstate 795Goldsboro, North Carolina to Interstate 40 west of Faison, North Carolina82U.S. Route 70U.S. 70 from Interstate 40 at Garner, North Carolina to the port of Morehead City, North Carolinalaw designates highway as a future Interstate highway (route number not specified in law). Assigned Interstate 42 by AASHTO83Sonoran Corridor (State Rte. 410)A new highway from Interstate 19 to Interstate 10 south of Tucson International Airport, Arizonalaw designates highway as a future Interstate highway (route number not specified in law)84Central Texas CorridorTwo routes from Interstate 10 (Pecos County) and Interstate 20 (Midland–Odessa), joining in Brady and continuing east to the Sabine River, passing in or near Fort Hood; College Station; Huntsville; and Livingston; all in Texas (paragraphs A–C) Also designates spurs from I-14 North in Eden to I-10 near Junction following U.S. 83 (paragraph D), from I-14 in Woodville to I-10 in Beaumont via U.S. 69 (paragraph E), from I-14 in Jasper to I-10 in Beaumont via U.S. 96 (paragraph F), and from I-20 in Odessa to I-10 in Pecos County via U.S. 385, RM 305, and U.S. 190 (paragraph G).FAST mandates that route be Interstate 14; IIJA designates Bryan–College Station loop as Interstate 214, the spur from Brady to I-10 as Interstate 14 South, and the spur from Brady to I-20 as Interstate 14 North. Routes in paragraphs D–G are designated as future Interstate highways (route number not specified in law)