The Washington metropolitan area has the worst traffic in the nation, and Northern Virginia is home to six of the ten worst bottlenecks in the area. To alleviate gridlock, local governments encourage using Metrorail, HOV, carpooling, slugging, and other forms of mass transportation. Major limited- or partially limited-access highways include Interstates 495 (the Capital Beltway), 95, 395, and 66, the Fairfax County Parkway and adjoining Franconia–Springfield Parkway, the George Washington Memorial Parkway, and the Dulles Toll Road. High-occupancy vehicle (HOV) lanes are used for commuters and buses on I-66, I-95/395, and the Dulles Toll Road. A study done by INRIX Roadway Analytics ranked Southbond I-95 from Washington D.C to the southern tip of Stafford County the worst single traffic hotspot in the nation. It also ranked Northbond I-95 from Spotsylvania County to the northern tip of Stafford County the seventh worst traffic hotspot in the nation. Northern Virginia is also home to the Express Lanes. These express lanes are where a car has a transbonder and is charged for riding a distance on the express lanes. They are currently being built on I-66, and are currently available on I-395, I-495 from the Springfield Interchange to Tysons Corner but are being extended to the Maryland-Virginia border, and I-95 from the end of I-395(Springfield Interchange) to central Stafford County and are being extended to Fredericksburg.