10 Busiest Interstates in the U.S.

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The names and numbers strike fear into the hearts of commuters and travelers across the United States. The Dan Ryan Expressway. I-95. The 405. The Connector. For all the benefits the U.S. Interstate Highway System has brought since its inception in 1956, it’s also created traffic congestion the system’s original designers could never have imagined. And it may get worse. Traffic officials warn the 47,182-mile system is showing signs of severe stress. Tens of billions of dollars are needed just to maintain existing interstates and bridges, and countless more billions are needed to widen and/or improve existing interstates to keep up with growing traffic. Following is a look at the 10 busiest interstates in America, based on federal and state highway statistics and other sources.


10. Interstate 85

The downtown connector in Atlanta is a notoriously congested stretch of interstate.

The I-85/I-75 connector in downtown Atlanta; Bright Atlanta/Brett Weinstein

Interstates ending in an odd number head north/south, while those ending in an even number are east/west routes, but some interstates are definitely tweeners. Interstate 85 runs almost directly northeast along its 669-mile route from Montgomery, Ala., almost to Richmond, Va. Along the way it runs through several dense metro areas, including Atlanta, Charlotte, the Piedmont Triad and the Raleigh/Durham area. The stretch through Atlanta carries more than a quarter-million vehicles per day, according to the Federal Highway Administration (FHWA), with several bottlenecks. The most notable is the infamous “downtown connector,” a 7.5-mile stretch of highway that carries both I-85 and I-75 through downtown Atlanta. Things don’t get much better away from the center city; a 2005 FHWA study rated Atlanta’s “Spaghetti Junction” interchange of I-85 and I-285 the second-most congested in the United States, costing truckers 1.66 million annual hours (the I-90/I-290 interchange in Buffalo, busy with commerce from Canada and Lake Erie, was rated No. 1). I-85 is a prime example of how interstates have spurred growth and development, and in turn, created their own traffic congestion, as the interstate has been credited in part with rapid population growth in Atlanta, Charlotte and Raleigh-Durham over the past half century.


9. Interstate 80

I-80 runs from coast to coast, but just misses some major metro areas.

I-80 (Eastshore Freeway) near Berkley, Calif., on a Saturday afternoon, 2005; Minesweeper

At almost exactly 2,900 miles in length, I-80 is the second-longest interstate in America, after I-90 (3,101 miles). Stretching from just outside New York City to downtown San Francisco, the highway just skirts some major metropolitan areas, notably Chicago and Cleveland, before its passage through remote stretches of the Great Plains and Rocky Mountains. The busiest stretch of I-80, known as the Eastshore Freeway in the San Francisco/Oakland area, carries almost 300,000 vehicles a day.


8. Interstate 10

I-10 passes through several of America's largest cities.

I-10 in Santa Monica; Florian

Sections of Interstate 10 in the Los Angeles and Phoenix areas both carry more than a quarter-million vehicles per day, but this highway also passes directly through several other densely populated areas, including Houston, San Antonio and New Orleans. In 2007, the U.S. Department of Transportation selected I-10 as one of six interstates in its “Corridors of the Future” program. These interstate routes were chosen as part of a federal initiative designed to find ways to use both public and private resources to reduce interstate congestion. The other interstates selected for the program are I-95, I-70, I-15, I-5 and I-69.


7. Interstate 45

I-45 connects the populous Houston and Dallas-Fort Worth metro areas.

I-45 and I-10 interchange in Houston; Dhanix

It goes without saying that any interstate connecting the megalopolises of Dallas/Fort Worth and Houston is going to be congested. I-45 in Houston carries more than 310,000 vehicles a day, making it the eighth-busiest interstate segment (That doesn’t even make it the busiest road in the Houston area; U.S. 59 carries about 13,000 more vehicles per day.) Perhaps surprisingly, the Dallas/Fort Worth metroplex, which has extremely heavy traffic during rush hours and even off-peak hours, has only one section of interstate on the FHWA’s list of the top 40 most-traveled urban highways; I-35E has 258,000 vehicles a day. Credit area officials who did a great job lobbying for funds to build an extensive road network in the region.


6. Interstate 110 (Southern California)

Interstate 110 is one of eight L.A. area roads among the 15 most traveled highways in the U.S.

I-110, the Harbor Freeway, in Los Angeles; Leslie

Better known as the Harbor Freeway, I-110 is only 32 miles in length, but the road carries some 328,000 vehicles per day in the Los Angeles-Long Beach-Santa Ana area, making it the fifth-busiest section of highway in the U.S. You’ve undoubtedly heard that heavy traffic is a part of life in L.A., but here is a mind-boggling statistic to underline the problem; according to the FHWA, eight of the top 15 most-traveled urban highways in America are in the L.A. metro area.


5. Interstate 15

Congestion on I-15 is a fact of life in San Diego, Las Vegas, Salt Lake City and several other cities.

I-15 in Salt Lake City; Garrett

Interstate 15 runs more than 1,470 miles from San Diego north to the Canadian border, through some of the most rugged and scenic country in America. But there are many heavily congested segments. I-15 in San Diego (295,000 vehicles per day), Las Vegas (263,000) and Salt Lake City (245,000 vehicles per day) are the three busiest sections, but there are other problem spots. The population in Mojave Desert communities such as Victorville, Hesperia and Adelanto has roughly doubled since the 2000 census, and many of these residents commute on I-15 to reach jobs in the Southern California metropolitan area. And anyone who’s ever left Southern Cal for a weekend in Las Vegas can attest to the heavy congestion both coming and going; the I-15 Mobility Alliance estimates around 8 million people each year use this highway between the two cities.


4. Interstate 90

I-90 is the bane of commuters and travelers in many cities across the U.S.

Traffic on I-90 waits to get through Snoqualmie Pass; Washington State DOT

Ask the average Chicagoland resident the best time to avoid bumper-to-bumper traffic on I-90, and the answer might be, “3 a.m.” The 7.5-mile section of I-90 co-signed with I-94 through Chicago, the Dan Ryan Expressway, carries almost 330,000 vehicles a day, making it the third-busiest stretch of interstate. The aforementioned FHWA study of congested highway interchanges placed the I-90/I-290 interchange as the fourth worst in the nation, and the I-94/I-90 interchange as the sixth worst. I-90 passes through several other major cities on its coast-to-coast route, including Boston, Buffalo, Cleveland and Seattle, but none of these segments approach Chicago-like traffic levels. One of the most notorious traffic nightmares on I-90 is far from any urban area. Traffic can back up more than 20 miles in the winter and early spring at treacherous Snoqualmie Pass in rural Washington State.


3. Interstate 5

Interstate 5 is the only interstate to touch both the Canadian and Mexican borders.

I-5 in Seattle; Cacophony

Interstate 5 originates at the world’s busiest border crossing, at San Ysidro on the Mexican border, and ends 1,381 miles away at the Canadian border, making it the only U.S. interstate to reach both countries. The segment of I-5 in Mission Viejo, roughly midway between L.A. and San Diego, is the second-busiest stretch of interstate in the U.S., with 334,000 vehicles per day. But parts of I-5 running through both San Diego and Los Angeles are both among the 20 busiest stretches of road in the country, carrying close to 300,000 vehicles daily. The California Department of Transportation is either performing or planning improvements at several points along I-5, which should help if they all come to pass. Traffic is much lighter after I-5 leaves Southern California on its way up the Pacific Coast, but Seattle adds more than a quarter-million vehicles into the I-5 mix each day, and Portland about half that figure.


2. Interstate 405 (Southern California)

Construction on the 405 in Southern California sparked fears of Carmageddon in 2011.

The 405; Steve Lyon

For the best illustration of how busy this road is, look no further than the story that made national news in 2011, when construction work shut down the 405 for a weekend, prompting fears of a so-called “Carmageddon.” Local residents stayed home, tourists huddled in their hotels, and the predictions of doom failed to materialize. FHWA statistics show the 72-mile 405, also known as the San Diego Freeway, is the busiest stretch of interstate in the country, with some 374,000 vehicles per day. Help is on the way, with improvements to a 10-mile stretch of the 405 through Sepulveda Pass in progress.


1. Interstate 95

Interstate 95 passes through the most densely populated part of the U.S.

I-95 crossing the George Washington Bridge in New York City; Wally Gobetz

A few stretches of interstate carry more traffic than the busiest parts of I-95, but no road in America is as consistently busy from one end to the other. I-95 runs from the Canadian border south to Miami, covering 1,917 miles and crossing through 15 states — the most of any interstate highway. According to the Federal Highway Administration, 1,040 of those miles are in urban areas, and more than 60 percent of those segments are classified as “under heavy congestion.” I-95 travels through the most densely populated region of the country in its northeast passage. More than 325,000 vehicles per day travel through the area encompassing the New York City/New Jersey/Connecticut area, making that stretch the seventh busiest in the country. It gets worse. I-95 passes through the Washington, D.C., area, another traffic chokepoint on the way to its southern terminus just south of Miami, where I-95 there rates as the sixth most-traveled section of interstate in the U.S. Florida’s 382-mile portion of the interstate is not just busy, it’s deadly — a Daily Beast study of federal data from 2004-2008 found I-95 in Florida to be the deadliest stretch of interstate highway in the U.S.


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The author is a longtime professional journalist who has interviewed everyone from presidential contenders to hall of fame athletes to rock 'n' roll legends while covering politics, sports, and other topics for both local and national publications and websites. His latest passions are history, geography and travel. He's traveled extensively around the United States seeking out the hidden wonders of the country.