Interstate 66
I-66 highlighted in red
Route information
Length	76.28 mi[1] (122.76 km)
Existed	1961–present
NHS	Entire route
Restrictions	No trucks on Custis Memorial Parkway or Theodore Roosevelt Bridge
Major junctions
West end	I-81 nearMiddletown, VA
Major intersections	US 340 /US 522 inFront Royal, VA US 17 /SR 55 inDelaplane, VA US 15 inHaymarket, VA US 29 inCentreville, VA SR 28 nearCentreville, VA SR 286 nearFair Oaks, VA US 50 inFair Oaks, VA I-495 inDunn Loring, VA SR 267 inIdylwood, VA
East end	US 29 inWashington, DC
Location
Country	United States
States	Virginia,District of Columbia
Counties	VA:Frederick,Warren,Fauquier,Prince William,Fairfax,Arlington DC:City of Washington
Highway system
Interstate Highway System Main Auxiliary Suffixed Business Future
Virginia Routes Interstate US Primary Secondary Byways History HOT lanes
Streets and Highways of Washington, DC Interstate US DC State-Named Streets
←SR 65 VA →SR 67 ←US 50 DC →I-95

Interstate 66 (I-66) is a 76.32 mile east–westinterstate highway in theeastern United States. The highway runs from an interchange withI-81 nearMiddletown, Virginia, on its western end to an interchange withU.S. Route 29 (US 29) inWashington, D.C., at the eastern terminus. The route parallelsState Route 55 (SR 55) from its western terminus at I-81 toGainesville, andUS 29 from Gainesville to its eastern terminus in Washington. I-66 is unrelated toUS 66, which was located in the Midwest-West region of the United States.

TheE Street Expressway is a spur from I-66 into theFoggy Bottom neighborhood of Washington, D.C.

I-66 begins at adirectional T interchange withI-81 nearMiddletown, Virginia. It heads east as a four-lane freeway and meetsUS 522/US 340 at apartial cloverleaf interchange. The two routes head south toFront Royal and north toLake Frederick. I-66 continues east and crosses theBlue Ridge atManassas Gap, parallelingSR 55 (John Marshall Highway) and meetingUS 17 at a partial interchange with no access from southbound US 17 to westbound I-66. SR 55 also merges onto the freeway at this interchange, forming a three-wayconcurrency that ends nearMarshall, with SR 55 leaving along withU.S. Route 17 Business (US 17 Bus.) and US 17 leaving at the next exit. The freeway then passes throughBull Run Mountain atThoroughfare Gap.

Expanding to six lanes, and continuing to parallel SR 55, I-66 enters the towns ofHaymarket andGainesville, reaching interchanges withUS 15 (James Madison Highway) andUS 29 (Lee Highway) in each town, respectively. The highway then expands to ten lanes and heads to the south ofManassas National Battlefield Park and to the north ofBull Run Regional Park. The highway reaches another interchange with US 29 and passes to the north ofCentreville and meetsSR 28 (Sully Road) at an interchange with cloverleaf and stack elements to it. SR 28 heads north toDulles International Airport and south toManassas.

The freeway then meetsSR 286 (Fairfax County Parkway),US 50 (Lee Jackson Memorial Highway), andSR 123 (Chain Bridge Road) at a series of interchanges providing access to D.C. suburbs. TheOrange Line andSilver Line of theWashington Metro begin to operate in the median here, as the highway reaches a large interchange with theI-495 (Capital Beltway).

I-66 has two tolledHOT lanes from US 29 in Gainesville to the Capital Beltway.^[2]

The section of I-66 in Virginia east of the Capital Beltway is named theCustis Memorial Parkway,^[3][4][5][6] atoll road with variable tolls during peak hours.^[7] The road narrows to four lanes as it heads throughArlington County. The parkway meetsSR 7 (Leesburg Pike) at a full interchange.SR 267 (Dulles Toll Road) meets the parkway with an eastbound entrance and westbound exit. Continuing through neighborhoods, the route yet again meets US 29 at an incomplete interchange and continues east into Arlington County, meetingSR 120 (Glebe Road) and continuing to Arlington County. It meetsSpout Run Parkway and entersRosslyn. The freeway turns southeast and runs in between US 29 as it approaches theTheodore Roosevelt Bridge, reaching another eastbound entrance and westbound exit as US 29 continues north on theKey Bridge. It then has a complex interchange withGeorge Washington Parkway andSR 110 (Richmond Highway), providing access toAlexandria andthe Pentagon, respectively. US 50 (Arlington Boulevard) merges onto the highway with a westbound exit and eastbound entrance and the two traverse the bridge.

The "Custis Memorial Parkway" name commemorates the Custis family, several of whose members (includingMartha Dandridge Custis Washington,George Washington Parke Custis,Eleanor "Nelly" Parke Custis Lewis andMary Anna Randolph Custis Lee) played prominent roles inNorthern Virginia's history. Because of its terminus in theShenandoah Valley, some early planning documents refer to I-66 as the "Shenandoah Freeway," although the name did not enter common use.^[8]

Between the Capital Beltway and the Theodore Roosevelt Bridge, the eastbound (inbound) roadway is ahigh-occupancy toll (HOT) road from 5:30 to 9:30 am, and the westbound (outbound) roadway is an HOT road from 3:00 to 7:00 pm. (Westbound tolling begins after exit 73 to US 29, in order to allow traffic crossing the bridge an opportunity to transfer to free roads.)E-ZPass is required for all vehicles except motorcycles, including Dulles Airport users. I-66 is free during those times for HOV-3+ drivers with an E-ZPass Flex and for motorcycles. Other drivers must pay a variable toll depending on traffic levels. Outside of these hours, I-66 is free for all drivers to use.^[9]

InWashington, D.C., the route quickly turns north, separating from US 50. The highway interchanges with the E Street Expressway spur before passing beneathVirginia andNew Hampshire Avenues in a short tunnel, also running on the east side of theWatergate complex. After an indirect interchange with theRock Creek and Potomac Parkway (via 27th Street), the highway terminates at a pair of ramps leading to the Whitehurst Freeway (US 29) and L Street. The portion of Interstate 66 within Washington, D.C., is known as the Potomac River Freeway.

TheE Street Expressway is a 480 meter long spur of I-66 that begins at an interchange with the interstate just north of the Roosevelt Bridge. It proceeds east, has an interchange with Virginia Avenue Northwest, and terminates at 20th Street Northwest. From there, traffic continues along E Street Northwest to 17th Street Northwest near theWhite House, theOld Executive Office Building,George Washington University, and theCorcoran Gallery of Art. Westbound traffic from 17th Street takes a one-block segment ofNew York Avenue to the expressway entrance at 20th and E streets northwest. The expressway and the connecting portions of E Street and New York Avenue are part of theNational Highway System.

In 1963, the construction of the E Street Expressway caused the demolition of multiple buildings of theOld Naval Observatory.^[11]

Exit list

The entire route is in theFoggy Bottom neighborhood ofWashington, D.C. All exits are unnumbered.

mi[10]	km	Destinations	Notes
0.00	0.00	I-66 toUS 29 south (Whitehurst Freeway) –Virginia	Western terminus
0.1	0.16	Virginia Avenue / 23rd Street	Eastbound exit only
0.1– 0.3	0.16– 0.48	Tunnel underneathVirginia Avenue
0.3	0.48	20th Street / E Street east	Eastern terminus;at-grade intersection
1.000 mi = 1.609 km; 1.000 km = 0.621 mi       Incomplete access

I-66 was first proposed in 1956—shortly afterCongress established the Highway Trust Fund—as a highway to connectStrasburg, Virginia, in the Shenandoah Valley with Washington, D.C..^[12][13]

During the planning stages, the Virginia Highway Department considered four possible locations for the highway inside the Beltway; in 1959, it settled on one that followed the Fairfax Drive–Bluemont Drive corridor between the Beltway andSR 120 (Glebe Road); and then along the Rosslyn Spur of theWashington and Old Dominion Railroad (W&OD) between Glebe Road andRosslyn inArlington County. The route west of 123 was determined earlier. Two other routes through Arlington neighborhoods and one along Arlington Boulevard were rejected due to cost or opposition.^[14] I-66 was originally to connect to theThree Sisters Bridge, but, as that bridge was canceled, it was later designed to connect to thePotomac River Freeway via the Theodore Roosevelt Bridge.^[15]

On December 16, 1961, the first piece of I-66, an 8.6-mile-long (13.8 km) section from US 29 atGainesville toUS 29 at Centreville was opened. A disconnected 3.3-mile-long (5.3 km) section nearDelaplane inFauquier County opened next in May 1962.^{[citation needed]}

In July 1962, the highway department bought the Rosslyn Spur of the W&OD for $900,000 (equivalent to $7.13 million in 2024^[16]) and began clearing the way, such that, by 1965, all that was left was dirt and the remains of 200 homes cleared for the highway.^[17][18][19] In February 1965, the state contracted to buy 30.5 miles (49.1 km) of the W&OD from Herndon to Alexandria for $3.5 million (equivalent to $26.5 million in 2024^[16]) and theChesapeake and Ohio Railway, by then the owners of the line, petitioned theInterstate Commerce Commission to let them abandon it. The purchase would eliminate the need to build grade separation where the railroad crossed I-66 and would provide 1.5 miles (2.4 km) of right-of-way for the highway, saving the state millions.^[20] The abandonment proceedings took more than three years, as customers of the railway and transit advocates fought to keep the railroad open and delayed work on the highway.^[21] During that time, on November 10, 1967, theWashington Metropolitan Area Transit Authority (WMATA) announced that it had come to an agreement with the Highway Department that would give them a two-year option to buy a five-mile (8.0 km) stretch of the right-of-way from Glebe Road to the Beltway, where I-66 was to be built, and run mass transit on the median of it.^[22] The W&OD ran its last train during the summer of 1968, clearing the way for construction to begin in Arlington County.

While the state waited on the W&OD, work continued elsewhere. The Theodore Roosevelt Bridge opened on June 23, 1964, and, in November of that year, the section from Centreville to the Beltway opened. A 0.2-mile (0.32 km) extension from the Roosevelt Bridge to Rosslyn opened in October 1966.

After theVirginia Department of Transportation (VDOT; then known as the Virginia Department of Highways) took possession of the mainline W&OD right-of-way in 1968, they began to run into opposition as thehighway revolts of the late 1960s and early 1970s took hold. In 1970, the Arlington County Board requested new hearings, and opponents began to organize marches.^[23][24] At the same time, the federal government wanted to pave the right-of-way from Washington Boulevard and Glebe Road to Rosslyn for an experimental busway, which Arlington County opposed, in part because they thought it might delay and add to the cost of I-66.^[25] A significant delay was encountered when theArlington Coalition on Transportation (ACT) filed a lawsuit inFederal District Court in 1971 opposing the Arlington County portion of the project. The group objected to that urban segment due to concerns overair quality,noise, unwanted traffic congestion, wasteful spending, impacts on mass transit, and wasted energy by auto travel.^[12] In 1972 theUS Fourth Circuit Court of Appeals ruled in favor of ACT, technically blocking any construction. TheUS Supreme Court upheld the ruling in favor of ACT later that same year.^[26]

Again, work continued elsewhere, and, in October 1971, the 6.6-mile-long (10.6 km) section from I-81 to US 340/US 522 north of Front Royal opened.

In July 1974, a finalenvironmental impact statement (EIS) was submitted.^[27] The EIS proposed an eight-lanelimited access expressway from theCapital Beltway to the area nearSpout Run Parkway.^[27] Six lanes would branch off at the Parkway and cross thePotomac River via a proposedThree Sisters Bridge.^[27] Another six lanes would branch off to theTheodore Roosevelt Bridge.^[27] In November, a modified design was submitted, reducing the eight lanes to six. However, in 1975, VDOT disapproved the six-lane design.^[27]

The parties then agreed on experts to conductair quality and noise studies for VDOT, selecting the firm ofESL Incorporated, the expert hired originally by ACT. In 1976,United States Secretary of TransportationWilliam Thaddeus Coleman Jr. intervened. On January 4, 1977, Coleman approved federal aid for a much narrower, four-lane limited access highway between the Capital Beltway and the Theodore Roosevelt Bridge.^[27] As part of the deal, Virginia officials agreed to provide more than $100 million (equivalent to $403 million in 2024^[16]) in construction work and funds to help build the Metro system, which has tracks down the I-66 median to a station atVienna in Fairfax County; to build amultiuse trail from Rosslyn to Falls Church; and to limit rush-hour traffic mainly to car pools.^[27][28][29] Three more lawsuits would follow, but work began on August 8, 1977, moments after US District Court Judge Owen R. Lewis denied an injunction sought by highway opponents.^[30]

In the late 1970s and early 1980s, the highway's final miles were built. A 2.9-mile-long (4.7 km) section from Delaplane to US 17 east of Marshall was completed in two sections in 1978 and 1979. The 15.6-mile-long (25.1 km) section from US 340 to Delaplane was completed in August 1979. A 12-mile (19 km) section between US 17 in Marshall and US 15 inHaymarket opened in December 1979, with the gap between Haymarket and Gainesville closed on December 19, 1980.^[31] On December 22, 1982, the final section of I-66 opened between the Capital Beltway and US 29 (Lee Highway) in Rosslyn, near the Virginia end of the Theodore Roosevelt Bridge.^[27]

TheCustis Trail, the trail along I-66 built between Rosslyn and Falls Church as a concession, opened in the summer of 1982, before the highway was complete.SR 267 (Dulles Access Road) between I-66 and the airport opened in 1984.^[27] The Metrorail in the median of I-66 betweenBallston and Vienna, another concession, opened on June 7, 1986.

After opening, the restrictions on use began to loosen. In 1983, Virginia dropped the HOV requirement from 4 to 3 and then from 3 to 2 in 1994. In 1992, motorcycles were allowed.^[27]

On October 9, 1999,Public Law 106-69 transferred from the federal government to theCommonwealth of Virginia the authority for the operation, maintenance, and construction of I-66 between Rosslyn and the Capital Beltway.^[32]

Because I-66 is the only Interstate Highway traveling west from Washington, D.C., intoNorthern Virginia, traffic on the road is often extremely heavy. For decades, there has been talk of widening I-66 from two to three lanes each way inside the Capital Beltway (I-495) through Arlington County, Virginia, although many Arlington residents are adamantly opposed to this plan. In 2004–2005, Virginia studied options for widening the highway inside the Beltway, including the prospect of implementing a one-lane-plus-shoulder extension on westbound I-66 within the Beltway (in an attempt to reduce congestion for people commuting away from D.C.).^[33] They later settled on three planned "spot improvements" meant to ease traffic congestion on westbound I-66 inside the Capital Beltway. The first improvement, a 1.9-mile (3.1 km) zone between Fairfax Drive and Sycamore Street, started in summer 2010 and was finished in December 2011. For this project, the entrance ramp acceleration lane and the exit ramp deceleration lanes were lengthened to form a continuous lane between both ramps. The 12-foot (3.7 m) shoulder lane can carry emergency vehicles and can be used in emergency situations.^[34][35] The second one widened 1.675 miles (2.696 km) between the Washington Boulevard onramp and the ramp to the Dulles Access Road. Work on it began in 2013 and finished in 2015.^[36] The third project, between Lee Highway/Spout Run and Glebe Road, was completed in 2022.^{[37][38][needs update]}

In Gainesville, Virginia, the Gainesville Interchange Project upgraded the interchange between US 29 and I-66 for those and many other roads due to rapid development and accompanying heavy traffic in the Gainesville and Haymarket area. I-66's overpasses were reconstructed to accommodate nine lanes (six general purpose, two HOV, and onecollector–distributor eastbound) and lengthened for the expansion of US 29 to six lanes. These alterations were completed in June 2010. In 2014–2015, US 29 was largely grade-separated in the area, including an interchange at its current intersection withSR 619 (Linton Hall Road). The project began in 2004 and finished in 2015.^[39]

TheVirginia Department of Transportation announced its public-private partnership with theVirginia Department of Rail and Public Transportation, and the private partner, I-66 Express Mobility Partners, with an estimating $3.7 billion dollars for transportation/road improvements along the I-66 corridor. The project, known as Transform 66, opened to traffic in November 2022 and the HOV rule changed from HOV-2+ to HOV-3+ in early December 2022.^[40]

In 2015, theVirginia Department of Transportation planning board added I-66 HOT lanes to their list of priority projects for the I-66 corridor.^[41] The projects have sparked opposition between residents and community businesses over the direction of this region's future infrastructure planning. The VDOT established a "Transform 66" website on regional traffic issues. Residents living within the I-66 corridor have set up "Transform 66 Wisely", a website describing local community impacts that the VDOT projects may cause. Local business groups andChambers of Commerce located near the affected areas, however, supported the improvements.^[42]

Residents along the I-66 corridor, such as in Arlington County, have resisted I-66 widening proposals for many years.^[43] The local Stenwood Elementary School would lose its attached field, leaving it with blacktop-only recess space.^[44] In an April 16, 2015, letter to the Virginia Secretary of Transportation, members of the 1st, 8th, 10th, and 11th districts of Congress wrote that VDOT research noted that, during peak hours, 35 percent of eastbound cars and 50 percent of westbound cars are HOV violators.

Future federal steps for VDOT includeNational Environmental Policy Act (NEPA) review, obligation of federal funds, certification that the conversion to tolled facilities will not "degrade" the existing facility, and potential federal loan guarantee. The Virginia Commonwealth Transportation Board (CTB) is responsible for overseeing VDOT and allocating highway funding to specific projects. The board has 18 members appointed by the Governor,^[45] includes the Virginia Secretary of Transportation,Aubrey Layne, and is the group that will be making the final decision and allocating funding for VDOT's plans for I-66.

In 2016, VDOT announced that it was planning to add express lanes and multimodal transportation improvements to I-66 outside the Beltway (the "Transform 66 Outside the Beltway" improvement project). A decision was also made to move forward with widening I-66 eastbound and make multimodal improvements from the Dulles Airport connector to Ballston, the "Transform 66 Inside the Beltway" improvement project.^[46]

VDOT also announced during 2016 that it would initiate on I-66 a dynamic tolling system in the peak travel directions during rush hours. On December 4, 2017, VDOT converted 10 miles (16 km) of I-66 between US 29 in Rosslyn and the Capital Beltway to an HOV variablecongestion pricing tolling system. The system permits solo drivers to use I-66 during peak travel hours in the appropriate direction if they pay a toll.^[47]

VDOT designed the price of toll to keep traffic moving at a minimum of 45 mph (72 km/h) and to increase the capacity of the road. Carpools and vanpools (with three or more people), transit, on-duty law enforcement and first responders do not pay a toll.^[48] Prices were as high as $47 one-way during the lanes' first weeks of operations, attracting controversy and national media attention. The average speed during the morning rush hour was 57 mph (92 km/h) versus 37 mph (60 km/h) a year before.^[49][50][51] In 2023, VDOT reported that the average charge to travel the length of the tolled section was $6.31 in mornings and $5.10 in evenings. 0.04% of trips cost more than $40, and it was the first time that any trips at all had crossed that amount since 2020.^[52]

In 2017, construction began on the "Transform 66 Outside the Beltway" improvement project.^[53] The project added 22.5 miles (36.2 km) of new dynamically-tolled express lanes alongside I-66 from I-495 to University Boulevard in Gainesville. It also built new park and ride facilities, interchange improvements and 11 miles (18 km) of expanded multi-use trail. The project was completed in November 2022.^[54]

Construction on widening eastbound I-66 as part of the "Transform 66 Inside the Beltway" improvement project began in June 2018 and was completed in 2020. The project added a travel lane on eastbound I-66 between the Dulles Access Road andFairfax Drive (exit 71) in Ballston, and provided a new ramp-to-ramp direct access connection from eastbound I-66 to theWest Falls Church station at the SR 7 interchange and provided a new bridge for theW&OD Trail over US 29.^{[48][needs update]}

VDOT completed in August 2018 adiverging diamond interchange in Haymarket at the interchange of I-66 withUS 15.^[55]

In Washington D.C., I-66 was planned to extend east of its current terminus along the North Leg of theInner Loop freeway. I-66 would have also met the eastern terminus of the plannedI-266 at US 29, and the western terminus ofI-695 (South Leg Freeway) at US 50; I-266 would have been a parallel route to I-66, providing more direct access to the North Leg from points west, while I-695 would have been an inner-city connector between I-66 and I-95.

The final plans for the North Leg Freeway, published in 1971, outlined a 1.5-mile (2.4 km) six-lane tunnel beneathK Street, between I-266/US 29 and New York Avenue, where the North Leg would emerge from the tunnel and join with theCenter Leg Freeway (formerly I-95, now I-395); the two routes would run concurrently for 0.75 miles (1.21 km) before reaching theWashington Union Station interchange, where I-66 was planned to terminate. Despite the plan to route the North Leg in a tunnel beneath K Street, the intense opposition to previous, scrapped alignments for the D.C. freeway network, which included previous alignments for the North Leg Freeway, led to the mass cancelation of all unbuilt D.C. freeways in 1977, resulting in the truncation of I-66 at US 29.

In 2023, as part of the Transform 66 – Outside the Beltway Project, a multi-use trail was built along the right-of-way from Gallows Road, located just outside the Beltway inDunn Loring to a point just west of Rt. 28 in Centreville.^[56] The trail is actually four separate trails connected by a combination of on-road bike facilities and sidewalks. There are plans to extend the trail further west to Sudley Road in Prince William County.^[57]

All exits in the District of Columbia are unnumbered.

State/district	County	Location	mi[58]	km	Old exit	New exit	Destinations	Notes
Virginia	Frederick	​	0.00	0.00		1	I-81 –Roanoke,Winchester	Western terminus; signed as exits 1A (south) and 1B (north); exit 300 on I-81;tri-stack interchange
	Warren	Front Royal	6.4	10.3	2	6	US 340 /US 522 –Winchester,Front Royal
		​	12.9	20.8	3	13	SR 79 toSR 55 –Linden,Front Royal
	Fauquier	Markham	18.5	29.8	4	18	SR 688 –Markham
		Delaplane	23.3	37.5	5	23	US 17 north /SR 55 west /SR 731 –Delaplane,Paris	Western terminus of US 17 / SR 55concurrency
		​	27.0	43.5	6	27	SR 55 east (US 17 Bus. south) /SR 647 –Marshall	Eastern terminus of SR 55 concurrency; formerSR 242 south
		​	28.3	45.5	7	28	US 17 south /US 17 Bus. north –Marshall,Warrenton,Fredericksburg	Eastern terminus of US 17 concurrency
		​	31.3	50.4	8	31	SR 245 –The Plains,Old Tavern
	Prince William	Haymarket	40.5	65.2	9	40	US 15 –Haymarket,Leesburg	Diverging diamond interchange
		​				♦	I-66 Express east	Western terminus of HOV3+/toll lanes
		Gainesville	43.1	69.4	10	43	US 29 –Gainesville,Warrenton	Signed as exits 43A (south) and 43B (north)
						♦	University Boulevard toUS 29	Westbound exit and eastbound entrance from HOV3+/toll lanes
		​	44.5	71.6	11	44	SR 234 south (Prince William Parkway) –Manassas,Dumfries	Western terminus of SR 234 concurrency
						♦	Balls Ford Road (SR 621)	Westbound exit and eastbound entrance from HOV3+/toll lanes
		​	47.3	76.1	12	47	SR 234 north /SR 234 Bus. south –Manassas,Manassas National Battlefield Park	Eastern terminus of SR 234 concurrency; signed as exits 47A (south) and 47B (north) westbound
						♦	SR 234 north /SR 234 Bus. south	Eastbound entrance to HOV3+/toll lanes
		​	48.8	78.5	Rest area
	Fairfax	Centreville	52.1	83.8	13	52	US 29 toSR 28 south –Centreville
		Centreville–Chantilly line	53.2	85.6	14	53B	SR 28 north –Dulles International Airport	Signed as exit 53 eastbound; no westbound entrance. Direct access to SR 620 (Braddock Rd), and SR 657 (Walney Rd); westbound entrance from SR 620
						53A	SR 28 south –Centreville	Westbound exit and eastbound entrance
							SR 28 north –Dulles International Airport	Access from HOV3+/toll lanes
		Fair Lakes	54.9	88.4		♦	Stringfellow Road (SR 645)	Westbound exit and eastbound entrance from HOV3+/toll lanes
			55.9	90.0	15	55	SR 286 (Fairfax County Parkway) –Springfield,Reston,Herndon	Signed as exits 55A (south) and 55B (north)
		Fair Oaks	57.1	91.9		♦	Monument Drive (SR 6751)	Access from HOV3+/toll lanes
			58.1	93.5	16	57	US 50 –Fair Oaks,Fairfax	Signed as exits 57A (east) and 57B (west)
							US 50 west –Fair Oaks	Westbound exit and eastbound entrance from HOV3+/toll lanes
		Module:Jctint/USA warning: Unused argument(s): exit
		Oakton	60.1	96.7	17	60	SR 123 –Fairfax,Vienna
							SR 123 –Fairfax,Vienna	Access via HOV3+/toll lanes
			Module:Jctint/USA warning: Unused argument(s): exit
						♦	Vaden Drive -Vienna/Fairfax-GMU Station	Eastbound exit and westbound entrance from HOV3+/toll lanes
		61.6	99.1	17A	62	Vienna/Fairfax-GMU Station	Accessible viaC/D lanes.Signed as 62A (Vienna/Fairfax - GMU) and 62B (Nutley Street) in the westbound direction
		Oakton–Merrifield line	62.5			100.6		SR 243 (Nutley Street) –Vienna,Fairfax
		Dunn Loring–Merrifield– Idylwood tripoint	65.1	104.8	18	64A	I-495 south –Richmond,Alexandria	Signed as exit 64 westbound; exit 49 on I-495
						64B	I-495 north –Tysons Corner,Baltimore	Eastbound exit and westbound entrance; exit 49 on I-495
						—	I-495 Express –Richmond,Baltimore	Eastbound exit and westbound entrance
						♦	I-495 /I-495 Express –Tysons Corner,Baltimore,Richmond,Alexandria	Eastbound exit and westbound entrance from HOV3+/toll lanes only
		Idylwood				♦	I-66 Express west	Eastern terminus of HOV3+/toll lanes
					Toll gantry (non-HOV3+ vehicles, peak-direction only)[9]
		Pimmit Hills–Idylwood line	66.0	106.2	19	66	SR 7 (Leesburg Pike) –Tysons Corner,Falls Church	Signed as exits 66A (east) and 66B (west) westbound; servesWest Falls Church station
	66.6		107.2	20	67	SR 267 west toI-495 north –Dulles International Airport,Baltimore	Westbound exit and eastbound entrance; eastern terminus of SR 267
	Westhampton			Toll gantry (non-HOV3+ vehicles, peak-direction only)[9]
	Arlington	East Falls Church	67.8	109.1	21	68	Westmoreland Street	Eastbound exit only
			68.4	110.1	22	69	US 29 /SR 237 (Washington Boulevard /Lee Highway)	Eastbound exit and westbound entrance; servesEast Falls Church station
					23	69	Sycamore Street –Falls Church	Westbound exit and eastbound entrance; servesEast Falls Church station
		Bluemont			Toll gantry (non-HOV3+ vehicles, peak-direction only)[9]
		Ballston	70.5	113.5	24	71	SR 120 (Glebe Road) /SR 237 (Fairfax Drive)	ServesBallston–MU station
		Cherrydale			Toll gantry (non-HOV3+ vehicles, peak-direction only)[9]
		Maywood	72.1	116.0	25	72	US 29 (Lee Highway) /Spout Run Parkway	Eastbound exit and westbound entrance
Rosslyn		73.1	117.6	26	73	US 29 (Lee Highway) –Rosslyn,Key Bridge
		74.2	119.4	27	75	SR 110 south –Pentagon,Alexandria	Eastbound exit and westbound entrance
Virginia–D.C. line	Arlington–Washington, D.C. line		74.8 0.0	120.4 0.0	Theodore Roosevelt Bridge over thePotomac River
			0.1	0.16		—	US 50 west (Arlington Boulevard) /George Washington Parkway north	Western terminus of US 50 concurrency; westbound exit and eastbound entrance
District of Columbia	Washington	Foggy Bottom	0.5	0.80		—	Independence Avenue	Eastbound exit only
						—	US 50 east (Constitution Avenue) –Downtown	Eastern terminus of US 50 concurrency; eastbound exit and westbound entrance
			0.7	1.1		—	E Street Expressway east	Western terminus of the E Street Expressway
			0.8	1.3		—	Kennedy Center	Westbound entrance only
			0.9	1.4		—	Independence Avenue /Maine Avenue	Westbound exit and eastbound entrance
			1.2	1.9		—	Rock Creek Parkway	Eastbound exit and westbound entrance
			1.4	2.3		—	Pennsylvania Avenue	Eastbound exit only
		Foggy Bottom–Georgetown line	1.6	2.6		—	Whitehurst Freeway (US 29 south) toCanal Road	Eastern terminus
1.000 mi = 1.609 km; 1.000 km = 0.621 mi       Concurrency terminus       Electronic toll collection       HOV only       Incomplete access

Interstate 266
Location	Arlington County, Virginia–Washington, D.C.
Length	1.79 mi (2.88 km)

Interstate 266 (I-266) was a proposed loop route of I-66 betweenWashington, D.C., andArlington County, Virginia. D.C. officials proposed designating the route Interstate 66N, a move opposed byAASHTO. In Virginia, I-266 would have split off from I-66 just east of the presentSR 124 (Spout Run Parkway) exit. From there, it would have followed an expanded Spout Run Parkway, crossed theGeorge Washington Memorial Parkway, and crossed thePotomac River across a new bridge that would have been called theThree Sisters Bridge. Upon entering D.C., it would have followedCanal Road and an expandedUS 29 (Whitehurst Freeway) to rejoin I-66 atK Street. I-266 was canceled in 1972 in the face of community opposition during Washington, D.C.'sfreeway revolts.^[59] It would have been the only auxiliary route of I-66.

Wikimedia Commons has media related toInterstate 66.

• Transform 66 Outside the Beltway Project
• HOV schedule in Northern Virginia, from Virginia Dept. of Transportation
• Steve Anderson's DCRoads.net: Interstate 66 (Virginia)

• Interstate 66
• Interstate Highways in Washington, D.C.
• Interstate Highways in Virginia
• Transportation in Frederick County, Virginia
• Transportation in Warren County, Virginia
• Transportation in Fauquier County, Virginia
• Transportation in Prince William County, Virginia
• Transportation in Fairfax County, Virginia
• Transportation in Arlington County, Virginia
• Cancelled highway projects in the United States

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