North Carolina Highway System

In the U.S. state of North Carolina, Interstate 77 (I-77) is a 105.7-mile (170.1 km) Interstate Highway, which serves the city of Charlotte and the Western Piedmont.

Interstate 77 begins at the South Carolina state line, near Fort Mill, in concurrency with US 21. I-77 goes through the city of Charlotte as a major north-south corridor, connecting the Center City with the suburbs of Pineville, Huntersville, Cornelius, and Davidson. Between I-485 (exit 2) and I-277 (exit 9), the freeway is 6-lanes that typically experience slow traffic congestion during weekday rush hours (7:00-9:30 a.m./4:00-6:30 p.m.). Just north of Center City, I-77 makes a unique interchange configuration with Interstate 85, with north and southbound lanes crisscrossing briefly. Between I-85 (exit 13) and I-485 (exit 19), I-77 features the state's only HOV lanes. After I-485, I-77 reduces to 5-lanes (3 lanes northbound), then to 4-lanes after Gilead Road (exit 23).

At Lake Norman, I-77 crosses into Iredell County and becomes a more rural interstate, passing by Mooresville and then Statesville, where it intersects with Interstate 40. After Statesville, I-77 becomes a full-fledged rural interstate, with only the town of Elkin serving as a possible rest stop in the area; the speed limit of entire stretch is 70 mph (110 km/h). The final 5 miles (8.0 km) of I-77 is concurrent with Interstate 74 to the Virginia state line (where I-74 ends), all within view of the Blue Ridge Mountains.

Interstate 77 has the first and only High occupancy vehicle (HOV) lanes in North Carolina, located in Mecklenburg County. They are open 24-hour/7 days a week and are closed for general traffic unless otherwise posted. They are identified by a "diamond" symbol and overhead signs and are located on the leftmost lanes. Vehicles with two or more occupants can use the HOV lanes. Emergency vehicles when responding to emergencies, mass transit vehicles, privately-owned buses, and motorcycles may also use the lanes. Violators are subject to a fine of up to $100 plus court costs; two points against their driver's licenses for each HOV infraction.

Though the highway is commonly known as "Interstate 77" or "I-77" throughout the state, the highway does have other known names it uses locally in areas.

Interstate 77 was not part of the original plans for 714 miles (1,149 km) of the nation's Interstate Highway System in North Carolina when they were conveyed in 1956 by the then-North Carolina State Highway Commission. I-77 was added in 1957, increasing the state's mileage to 776 miles (1,249 km).

On 4 August 1959, the commission selected the routing of I-77 to run between Interstate 85 in Charlotte and a point on the Virginia border in Elkin. That would change in late 1960, when the commission voted to route the highway just west of Mount Airy, saying the route would serve the most people.

With construction beginning in the 1960s, I-77 would gain additional mileage in October 1964 when a two-mile (3 km) extension was granted by the U.S. Bureau of Public Roads. Instead of ending at I-85, I-77 now ended at Independence Boulevard (U.S. 74) in downtown Charlotte. Another extension was granted in the late 1960s that extended I-77 from Independence Boulevard to the South Carolina border. The latest extension also included a relocation of U.S. 21 from the city's surface streets to the new interstate.

I-77 opened to traffic in the following segments:

By 1972, I-77 was open from Exit 28 (NC 73) to Exit 73 north of Elkin. The last two sections of the highway to open to traffic was the stretch from Cornelius to Charlotte in 1975 and from Exit 73 to the Virginia state line in 1977.

In April 2001, I-74 was overlapped with I-77 from the Virginia state line to exit 101.

On 17 December 2004, I-77 was widened to six-lanes with HOV lanes, between I-85 to the proposed location of I-485 (later opened 8 December 2008).

Interstate 77 is planned to have its existing southbound travel lanes widened (not add more lanes), between I-277/NC 16 (Brookshire Freeway) to I-85 in Charlotte. Estimated to cost $16.5 Million, the purpose of the project is to widen the lanes back to proper Interstate standards as agreed with FHWA, when NCDOT were given design exceptions when adding the HOV lanes in 2004. Construction is tentatively scheduled for 2016.

Currently in the development stage, HOT lanes are planned to be added along Interstate 77. The project is broken into two parts: the first is constructing new travel lanes from I-485 interchange (exit 19) to West Catawba Avenue (exit 28), it has an estimated cost of $57 million with construction beginning in 2014. The second would be to convert the existing HOV lanes from Brookshire Boulevard (exit 11) to I-485 (exit 19). After completion, drivers and motorcyclists can still use the lane for free if qualified under HOV rules, non-compliant drivers will be charged a toll.

The I-40/I-77 interchange (exit 51) is planned for major upgrade in three phases: reconstruction of nearby intersections on both interstates, reconstruction and widening of I-40/I-77 interchange, and construction of fly-overs at interchange. The estimated cost for the entire project is $251 million with construction to begin in March 2012. It will replace the current interchange, which was built in the late 1960s.