Many of us rely on our cars to get from point A to point B every day, which means it’s rare for us to find ourselves alone on a highway. The Interstate Highway System was created in 1956, and since then, the U.S. has built a vast network of ever-busier roads, carrying commuters, vacationers, and commercial traffic alike. But have you ever stopped to wonder which roads are the busiest? Luckily, the Federal Highway Administration (FHWA) has compiled a list of the country’s busiest roads, based on a metric the agency calls Annual Average Daily Traffic (AADT). Read on to learn which routes rank in the top 15 busiest highways in America.
15. Interstate 10 – Houston, Texas
Total route length: 2,640 miles
Daily vehicle volume in Houston segment: 320,892
The fourth-longest route in the Interstate Highway System, I-10 is the main interstate crossing the southern U.S. From where it meets California Route 1 in Santa Monica, I-10 extends 2,640 miles to Jacksonville, Florida, including an 880-mile stretch through Texas. The portion of I-10 passing through Houston is one of the nation’s most traffic-clogged highways. Known locally as the Katy Freeway, it is also one of the widest roads in the world, spanning a staggering 26 lanes of traffic. Over 320,000 vehicles use it daily, making this the busiest road in the Lone Star State.
14. California State Route 91 – Los Angeles, California
Total route length: 59 miles
Daily vehicle volume in busiest segment: 319,000
Whichever route daily commuters choose in the Greater Los Angeles area, traffic is all but certain. The first of two California state highways on the list, State Route 91 connects the cities of Gardena and Riverside. Various segments are known by different names, including the Gardena, Artesia, and Riverside Freeways. California 91 was originally part of a longer road, U.S. Route 91, which was intended to go as far as Las Vegas. Over the years, however, parts have been rerouted or decommissioned. In 1963, the California road became a state highway instead.
13. Interstate 10 – Phoenix, Arizona
Total route length: 2,640 miles
Daily vehicle volume in Phoenix segment: 318,542
Busy I-10 passes through three of the nation’s five largest cities, including Phoenix, Arizona. The part that enters Phoenix from the east is called the Maricopa Freeway. It winds its way through intersections with various highways before exiting the Phoenix metro area and continuing west to Los Angeles. Interstates arrived relatively late in Arizona compared to other parts of the country, but the traffic now rivals that of the busiest states.
12. U.S. Route 101 – Los Angeles, California
Total route length: 1,540 miles
Daily vehicle volume in busiest segment: 318,000
U.S. Route 101 is one of the oldest numbered U.S. highways in existence. Established in 1926, three decades before the arrival of the Interstate Highway System in 1956, it once ran from the Mexican border up the West Coast to Olympia, Washington. Parts have since been decommissioned in favor of larger interstates; however, it remains a key route for the region. North of San Francisco, U.S. 101 is called the Redwood Highway. The stretch around Los Angeles is called El Camino Real (the King’s Highway), and it follows the route of early 18th-century Spanish explorers.
11. Interstate 69 – Houston, Texas
Total route length: 880 miles
Daily vehicle volume in busiest segment: 316,892
With its earliest segment dating to 1957, Interstate 69 runs from Port Huron, Michigan, to Laredo, Texas. However, the highway is being expanded and some parts of the route are still under construction. I-69 passes through Indiana, Kentucky, Tennessee, and Mississippi, with plans for additional sections through Arkansas and Louisiana. The expanded route is nicknamed the NAFTA Superhighway, since it will eventually connect Canada with Mexico. The 75-mile stretch through Houston, Texas — formerly named U.S. Route 59 — sees upwards of an estimated 316,000 vehicles every day.
10. Interstate 90 – Chicago, Illinois
Total route length: 3,021 miles
Daily vehicle volume in busiest segment: 321,700
Interstate 90 is the longest route in the Interstate Highway System, stretching from Boston to Seattle. Driving the entire length of I-90 would take you approximately 50 hours, and you’d travel through 13 states, including New York, Pennsylvania, and Idaho. However, you should be prepared for possible delays as you drive through Chicago. An estimated 321,700 vehicles use the Windy City’s segment of I-90 each day, making it the 10th-busiest highway in the nation.
9. Interstate 15 – Las Vegas, Nevada
Total route length: 1,433 miles
Daily vehicle volume in busiest segment: 332,000 vehicles
Interstate 15 was originally intended to begin in San Bernardino, California, located east of Los Angeles, but the decision was later made to extend its origin south to San Diego. The highway ends at the Canadian border, where it joins Alberta Highway 4. A 124-mile stretch of I-15 through Nevada passes right through Las Vegas. Its proximity to the Strip, along with its connection to Los Angeles and Sin City, makes this a busy segment of road for tourists and business travelers alike.
8. Interstate 95 – Miami, Florida
Total route length: 1,917 miles
Daily vehicle volume in busiest segment: 339,500
Driven by commerce and vacationers alike, Interstate 95 passes through 16 states, more than any other U.S. highway. It runs the entire length of the East Coast, from the Maine-Canada border to Florida. As such, it is a popular route for so-called “snowbirds,” those who head south for warmer winters. I-95 ends in Miami, where it becomes U.S. Highway 1 — aka the Overseas Highway — and continues to Key West, home to the southernmost point in the contiguous U.S. The terminus of I-95 in Miami is Florida’s — and one of the nation’s — busiest stretches of highway, with 339,500 average daily vehicles.
7. California State Route 60 – Los Angeles, California
Total route length: 76 miles
Daily vehicle volume in busiest segment: 350,000
California State Route 60 is the only highway that ranks in the top 10 busiest highways in the U.S. that is not an interstate highway. The route is also known in parts as the Pomona Freeway and the Moreno Valley Freeway. It runs east from Los Angeles along the southern side of the San Gabriel Valley to meet I-215 in Riverside. L.A. traffic is notoriously heavy, and CA-60 is no exception. It is one of five L.A. highways to appear on this list.
6. Interstate 10 – Los Angeles, California
Total route length: 2,640 miles
Daily vehicle volume in busiest segment: 355,000
Interstate 10 makes a third appearance on the list of U.S. highways with the worst traffic. This part of the highway runs from the coastal city of Santa Monica, located west of downtown Los Angeles, into East L.A. Better known as the Santa Monica Freeway, it is one of the busiest commuter routes in Southern California.
5. Interstate 210 – Los Angeles, California
Total route length: 85 miles
Daily vehicle volume in busiest segment: 358,000
Running along the northern borders of Los Angeles, from the city of Sylmar to Glendora, is Interstate 210. Along the way, the highway, also known as the Foothill Freeway, passes through Pasadena, home of the annual Rose Bowl. Despite its relatively short length, I-210 is incredibly busy — with some 358,000 commuters driving along it every day.
4. Interstate 405 – Los Angeles, California
Total route length: 72 miles
Daily vehicle volume in busiest segment: 383,500
Interstate 405 is the main north-south artery through the city of Los Angeles, connecting Irvine in Orange County with San Fernando in the Valley. It is a key route from L.A. to the Port of Long Beach and Los Angeles International Airport (LAX). As such, “the 405” — as locals call it — is frequently named one of the most congested highways in the world. A local joke is that its name refers to the maximum speed — just 4 or 5 mph, thanks to the 383,500 vehicles trying to use the freeway on an average day.
3. Interstate 5 – Mission Viejo, California
Total route length: 1,381 miles
Daily vehicle volume in this segment: 415,000
Interstate 5 runs along the entire West Coast, connecting the Mexican and Canadian borders. The route — one of the top three busiest highways in the U.S. — also connects California’s three biggest metro areas: San Francisco, Los Angeles, and San Diego. The segment through Orange County, south of Los Angeles, is one of the busiest, particularly as it passes through the city of Mission Viejo. Here, local commuter traffic and longer-distance commercial traffic are often caught in congestion, which makes its one of the three busiest highways in the U.S. A major construction project to widen the road is currently underway as of 2024.
2. Interstate 75 – Atlanta, Georgia
Total route length: 1,786 miles
Daily vehicle volume in busiest segment: 419,516
Like I-95, Interstate 75 is a major north-south route, connecting the Great Lakes to Florida via cities such as Detroit, Cincinnati, and Atlanta. The highway carries so much traffic that much of its Georgia portion is six lanes wide. In Atlanta, I-75 joins with I-85 for a 7.4-mile segment known as the Downtown Connector with a whopping 16 lanes. The large number of lanes is necessary, given that this is the second-busiest stretch of highway in the United States, seeing over 400,000 vehicles on an average day.
1. Interstate 5 – Los Angeles and Santa Ana, California
Total route length: 1,381 miles
Daily vehicle volume in busiest segment: 504,000
Interstate 5 has already been mentioned as one of the top three busiest highways in the U.S., but another segment of this notoriously congested highway lands at No. 1 on the list. Just north of Mission Viejo, I-5 becomes the Santa Ana Freeway, linking Orange County to metro L.A. Several popular tourist attractions are also in this area, including Disneyland. When commuter and business traffic is combined with visiting vehicles, it adds up to the most congested road in the entire country, with over 500,000 vehicles trying to drive it on any given day.
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