Interstate 66 (I-66): Express Lane Tolls, Route, Length and Safety Data

How long is I-66?

The Route Log, FHWA's federal mileage table as of January 2026, gives I-66 a total of 75.78 miles. Virginia has 74.77 of them and the District of Columbia 1.01. The Route Log records no stretch of I-66 shared with another Interstate.

Wikipedia's infobox and Interstate Guide both put the road at 76.28 miles, half a mile more. The two agree with the federal figure for Virginia to within a few hundredths of a mile, so the difference sits in the District. Interstate Guide counts 1.48 miles there, and Wikipedia's length table shows 1.6. Neither source says why its DC figure is longer.

Where I-66 starts and ends

I-66 begins at a directional T interchange with I-81 near Middletown, in Frederick County, Virginia, near Strasburg. It ends in Washington's Foggy Bottom and Georgetown area at US 29, where ramps reach K Street, L Street, the Whitehurst Freeway and Rock Creek Parkway.

Eastbound, the road passes Front Royal, crosses the Blue Ridge at Manassas Gap and cuts through Bull Run Mountain at Thoroughfare Gap. Haymarket, Gainesville and Centreville come next. Inside the Beltway, Virginia calls I-66 the Custis Memorial Parkway; it passes East Falls Church, Ballston and Rosslyn, then shares the Theodore Roosevelt Bridge with US 50 to cross the Potomac. In the District it becomes the Potomac River Freeway, running past the Kennedy Center and the Watergate.

Interstate junctions along I-66

The junction table has one entry, I-81, where I-66 begins. Heading east, I-66 also meets I-495, the Capital Beltway, at Dunn Loring in Fairfax County. That interchange is the dividing line between the two express lane systems. East of the Beltway, an exit at Idylwood connects to Virginia Route 267 toward Dulles. West of it, Virginia 28 meets the road at Centreville, and the US 15 interchange at Haymarket became a diverging diamond in August 2018.

Fatal crashes on I-66

NHTSA's FARS records 25 fatal crashes on the I-66 main line from 2020 to 2024, and they killed 29 people, an average of about six a year. The site ranks death rates only for the 56 Interstates of 100 miles or more, and at 75.78 miles I-66 is too short to qualify, so it has no rate here.

Fairfax County had 10 deaths. Fauquier followed with 6, Warren and Prince William had 5 each and Arlington had 2. Those five counties account for all 28 Virginia deaths, so Frederick County at the western end had none; the District had 1. The yearly count jumped from 1 in 2020 to 9 in 2021, then ran 7, 5 and 7. NHTSA still lists the 2024 count as preliminary.

Counties with the most I-66 crash deaths

Bridges on I-66

The 2025 National Bridge Inventory lists 114 bridges carrying the I-66 main line. Just 1 is rated Poor, and it is one of the 5 in the District of Columbia. None of the 109 Virginia bridges rates Poor. Most of the bridges are rated Fair, 96 of them, against 17 Good. Half were built in 1979 or earlier, near the end of a construction period that ran from 1961 to 1982.

The Theodore Roosevelt Bridge, which carries I-66 and US 50 over the Potomac, opened on June 23, 1964. Trucks are barred from the bridge and from the Custis Memorial Parkway in Arlington. On the District side, the freeway dips through a short tunnel under Virginia and New Hampshire Avenues.

Tolls on I-66

FHWA's toll inventory for January 2023 lists two I-66 facilities, both express lanes. VDOT runs the lanes inside the Beltway, from I-495 to US 29 in Rosslyn. Express Mobility Partners runs the lanes outside it, west to US 29 at Gainesville. An eastbound trip from I-81 into Washington costs nothing if the driver keeps to the regular lanes outside the Beltway and reaches Arlington outside the weekday morning toll period. FHWA's table gives each facility's own length: 10.0 miles inside and 22.4 outside, while ARLnow calls the inner stretch nine miles and Interstate Guide puts the outer one at 22.5.

Inside the Beltway, tolls apply on non-holiday weekdays in the peak direction only: eastbound from 5:30 to 9:30 a.m. and westbound from 3 to 7 p.m. During those hours every lane in that direction is an express lane, so solo drivers need an E-ZPass and pay the toll posted on the signs. Vehicles with three or more people ride free if they carry an E-ZPass Flex switched to HOV mode; that HOV-3 rule replaced HOV-2 on December 5, 2022. Motorcycles also ride free. The price changes with traffic volume and speed. Wikipedia gives 2023 averages of $6.31 for the full tolled section in the morning and $5.10 in the evening, and says one-way tolls reached $47 soon after tolling began in December 2017.

Outside the Beltway, two tolled express lanes run beside three regular lanes in each direction for about 22.5 miles, from I-495 to Gainesville. The $3.7 billion project opened in stages, starting in September 2022, and was fully open on November 22, 2022. Rates there rise and fall to keep the express lanes moving at 55 mph, and HOV-3 vehicles with an E-ZPass Flex pay nothing. TollGuru, a toll calculator service, says this section is tolled around the clock, unlike the inner lanes.

How I-66 got through Arlington

I-66 was first proposed in 1956 to link Strasburg with Washington, and it became part of the Interstate system on August 14, 1957. The first 8.6 miles, Gainesville to Centreville, opened on December 16, 1961. The Theodore Roosevelt Bridge opened in June 1964, and that November the road reached the Beltway from Centreville. The western end, from I-81 to US 340/522 near Front Royal, opened in October 1971, and the last rural gap, between Haymarket and Gainesville, closed on December 19, 1980.

Arlington took far longer. Virginia bought the W&OD Railway's Rosslyn spur for $900,000 in July 1962 as a path for the freeway, but the last W&OD train did not run until 1968, and local opposition grew after that. The Arlington Coalition on Transportation sued and won in the Fourth Circuit in 1972, and the Supreme Court declined to hear the state's appeal. On January 4, 1977, Transportation Secretary William T. Coleman Jr. approved a narrower four-lane road between the Beltway and the Roosevelt Bridge (Interstate Guide dates the decision January 5). Work began that August, and the section from the Beltway to US 29 in Rosslyn opened on December 22, 1982.

At rush hour the Arlington segment was first open only to vehicles with four or more people, along with buses, airport traffic and emergency vehicles. The rule eased to HOV-3 in 1983 and HOV-2 in 1994. Variable tolls started on December 4, 2017, and the eastbound side was widened from 2018 to 2020.

Some planned pieces were never built. A spur numbered I-266 would have crossed the Potomac on a new Three Sisters Bridge; it was canceled in 1972 during Washington's freeway revolts, and the remaining District extensions of I-66 were withdrawn in 1977. In the early 1990s, Wichita business leaders pushed a cross-country I-66 from Fresno, California, to Washington. A 2001 federal spending bill added I-66 mileage in Kentucky and set aside $22.5 million for the route, and Kentucky posted future I-66 signs on the Cumberland Parkway on March 23, 2005, but Interstate Guide reports that no construction followed.

I-66 traffic and road conditions

Crash counts on this page stop at 2024, so they say nothing about this morning's backup at the Beltway. For current wrecks, lane closures and work zones on the Virginia side, which is nearly all of I-66, use the 511 Virginia link below.

I-66 questions