Interstate 66 (I-66) is a 76.32 mile east–west
Interstate Highway
The Dwight D. Eisenhower National System of Interstate and Defense Highways, commonly known as the Interstate Highway System, or the Eisenhower Interstate System, is a network of controlled-access highways that forms part of the National Hi ...
in the
eastern United States. The highway runs from an interchange with
I-81 near
Middletown, Virginia, on its western end to an interchange with
U.S. Route 29 (US 29) in
Washington, D.C., at the eastern terminus. The route parallels
State Route 55 (SR 55) from its western terminus at I-81 to
Gainesville, and
US 29 from Gainesville to its eastern terminus in Washington. I-66 is unrelated to
US 66, which was located in the Midwest-West region of the United States.
The E Street Expressway is a spur from I-66 into the
Foggy Bottom neighborhood of Washington, D.C.
Route description
, -
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VA
, 74.8
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DC
, 1.6
, 2.57
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, 76.4
, 123.11
Virginia
Interstate 81 to Dunn Loring
I-66 begins at a
directional T interchange with
I-81 near
Middletown, Virginia. It heads east as a four-lane freeway and meets
US 522/
US 340 at a
partial cloverleaf interchange. The two routes head south to
Front Royal and north to
Lake Frederick. I-66 continues east and crosses the
Blue Ridge at
Manassas Gap, paralleling
SR 55 (John Marshall Highway) and meeting
US 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-way
concurrency that ends near
Marshall, with SR 55 leaving along with
U.S. Route 17 Business (US 17 Bus.) and US 17 leaving at the next exit. The freeway then passes through
Bull Run Mountain at
Thoroughfare Gap.
Expanding to six lanes, and continuing to parallel SR 55, I-66 enters the towns of
Haymarket and
Gainesville, reaching interchanges with
US 15 (James Madison Highway) and
US 29 (Lee Highway) in each town, respectively. The highway then expands to ten lanes and heads to the south of
Manassas National Battlefield Park and to the north of
Bull Run Regional Park. The highway reaches another interchange with US 29 and passes to the north of
Centreville and meets
SR 28 (Sully Road) at an interchange with cloverleaf and stack elements to it. SR 28 heads north to
Dulles International Airport and south to
Manassas.
The freeway then meets
SR 286 (
Fairfax County Parkway),
US 50 (Lee Jackson Memorial Highway), and
SR 123 (
Chain Bridge Road) at a series of interchanges providing access to D.C. suburbs. The
Orange Line and
Silver Line of the
Washington Metro begin to operate in the median here, as the highway reaches a large interchange with the
I-495 (
Capital Beltway).
I-66 has two tolled
HOT lanes from US 29 in Gainesville to the Capital Beltway.
Dunn Loring to Theodore Roosevelt Bridge
The section of I-66 in Virginia east of the Capital Beltway is named the Custis Memorial Parkway, a
toll road
A toll road, also known as a turnpike or tollway, is a public or private road for which a fee (or ''Toll (fee), toll'') is assessed for passage. It is a form of road pricing typically implemented to help recoup the costs of road construction and ...
with variable tolls during peak hours. The road narrows to four lanes as it heads through
Arlington County. The parkway meets
SR 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, meeting
SR 120 (Glebe Road) and continuing to Arlington County. It meets
Spout Run Parkway and enters
Rosslyn. The freeway turns southeast and runs in between US 29 as it approaches the
Theodore Roosevelt Bridge, reaching another eastbound entrance and westbound exit as US 29 continues north on the
Key Bridge. It then has a complex interchange with
George Washington Parkway and
SR 110 (Richmond Highway), providing access to
Alexandria
Alexandria ( ; ) is the List of cities and towns in Egypt#Largest cities, second largest city in Egypt and the List of coastal settlements of the Mediterranean Sea, largest city on the Mediterranean coast. It lies at the western edge of the Nile ...
and
the Pentagon
The Pentagon is the headquarters building of the United States Department of Defense, in Arlington County, Virginia, across the Potomac River from Washington, D.C. The building was constructed on an accelerated schedule during World War II. As ...
, 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 (including
Martha Dandridge Custis Washington,
George Washington Parke Custis,
Eleanor "Nelly" Parke Custis Lewis and
Mary Anna Randolph Custis Lee) played prominent roles in
Northern Virginia
Northern Virginia, locally referred to as NOVA or NoVA, comprises several County (United States), counties and independent city (United States), independent cities in the Commonwealth (U.S. state), Commonwealth of Virginia in the United States. ...
's history. Because of its terminus in the
Shenandoah Valley, some early planning documents refer to I-66 as the "Shenandoah Freeway", although the name did not enter common use.
Between the Capital Beltway and the Theodore Roosevelt Bridge, the eastbound (inbound) roadway is a
high-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 current traffic levels. Outside of these hours, I-66 is free for all drivers to use.
Washington, D.C.
In
Washington, D.C., the route quickly turns north, separating from US 50. The highway interchanges with the E Street Expressway spur before passing beneath
Virginia
Virginia, officially the Commonwealth of Virginia, is a U.S. state, state in the Southeastern United States, Southeastern and Mid-Atlantic (United States), Mid-Atlantic regions of the United States between the East Coast of the United States ...
and
New Hampshire Avenues in a short tunnel, also running on the east side of the
Watergate complex. After an indirect interchange with the
Rock 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, DC, is known as the Potomac River Freeway.
E Street Expressway
The E 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 the
White House
The White House is the official residence and workplace of the president of the United States. Located at 1600 Pennsylvania Avenue Northwest (Washington, D.C.), NW in Washington, D.C., it has served as the residence of every U.S. president ...
, the
Old Executive Office Building,
George Washington University
The George Washington University (GW or GWU) is a Private university, private University charter#Federal, federally-chartered research university in Washington, D.C., United States. Originally named Columbian College, it was chartered in 1821 by ...
, and the
Corcoran Gallery of Art. Westbound traffic from 17th Street takes a one-block segment of
New 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 the
National Highway System.
In 1963, the construction of the E Street Expressway caused the demolition of multiple buildings of the
Old Naval Observatory.
;Exit list
The entire route is in the
Foggy Bottom neighborhood of
Washington, D.C. All exits are unnumbered.
History
Virginia

I-66 was first proposed in 1956 shortly after
Congress established the Highway Trust Fund as a highway to connect
Strasburg, Virginia, in the Shenandoah Valley with Washington, D.C..
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 and
SR 120 (Glebe Road); and then along the Rosslyn Spur of the
Washington and Old Dominion Railroad (W&OD) between Glebe Road and
Rosslyn in
Arlington 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. I-66 was originally to connect to the
Three Sisters Bridge, but, as that bridge was canceled, it was later designed to connect to the
Potomac River Freeway via the Theodore Roosevelt Bridge.
On December 16, 1961, the first piece of I-66, an section from US 29 at
Gainesville to
US 29 at Centreville was opened. A disconnected section near
Delaplane in
Fauquier County opened next in May 1962.
In July 1962, the highway department bought the Rosslyn Spur of the W&OD for $900,000 (equivalent to $ in ) 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. In February 1965, the state contracted to buy of the W&OD from Herndon to Alexandria for $3.5 million (equivalent to $ in ) and the
Chesapeake and Ohio Railway, by then the owners of the line, petitioned the
Interstate Commerce Commission
The Interstate Commerce Commission (ICC) was a regulatory agency in the United States created by the Interstate Commerce Act of 1887. The agency's original purpose was to regulate railroads (and later Trucking industry in the United States, truc ...
to let them abandon it. The purchase would eliminate the need to build grade separation where the railroad crossed I-66 and would provide of right-of-way for the highway, saving the state millions. 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. During that time, on November 10, 1967, the
Washington 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 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. 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 extension from the Roosevelt Bridge to Rosslyn opened in October 1966.
After the
Virginia 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 the
highway 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. 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. A significant delay was encountered when the
Arlington Coalition on Transportation (ACT) filed a lawsuit in
Federal District Court in 1971 opposing the Arlington County portion of the project. The group objected to that urban segment due to concerns over
air quality,
noise
Noise is sound, chiefly unwanted, unintentional, or harmful sound considered unpleasant, loud, or disruptive to mental or hearing faculties. From a physics standpoint, there is no distinction between noise and desired sound, as both are vibrat ...
, unwanted traffic congestion, wasteful spending, impacts on mass transit, and wasted energy by auto travel.
In 1972 the
US Fourth Circuit Court of Appeals ruled in favor of ACT, technically blocking any construction. The
US Supreme Court
The Supreme Court of the United States (SCOTUS) is the highest court in the federal judiciary of the United States. It has ultimate appellate jurisdiction over all Federal tribunals in the United States, U.S. federal court cases, and over Stat ...
upheld the ruling in favor of ACT later that same year.
Again, work continued elsewhere, and, in October 1971, the section from I-81 to US 340/US 522 north of Front Royal opened.
In July 1974, a final
environmental impact statement (EIS) was submitted.
The EIS proposed an eight-lane
limited access expressway from the
Capital Beltway to the area near
Spout Run Parkway.
Six lanes would branch off at the Parkway and cross the
Potomac River
The Potomac River () is in the Mid-Atlantic (United States), Mid-Atlantic region of the United States and flows from the Potomac Highlands in West Virginia to Chesapeake Bay in Maryland. It is long,U.S. Geological Survey. National Hydrography D ...
via a proposed
Three Sisters Bridge.
Another six lanes would branch off to the
Theodore Roosevelt Bridge.
In November, a modified design was submitted, reducing the eight lanes to six. However, in 1975, VDOT disapproved the six-lane design.
The parties then agreed on experts to conduct
air quality and noise studies for VDOT, selecting the firm of
ESL Incorporated, the expert hired originally by ACT. In 1976,
United States Secretary of Transportation
The United States secretary of transportation is the head of the United States Department of Transportation. The secretary serves as the principal advisor to the president of the United States on all matters relating to transportation. The secre ...
William 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.
As part of the deal, Virginia officials agreed to provide more than $100 million (equivalent to $ in ) in construction work and funds to help build the Metro system, which has tracks down the I-66 median to a station at
Vienna
Vienna ( ; ; ) is the capital city, capital, List of largest cities in Austria, most populous city, and one of Federal states of Austria, nine federal states of Austria. It is Austria's primate city, with just over two million inhabitants. ...
in Fairfax County; to build a
multiuse trail from Rosslyn to Falls Church; and to limit rush-hour traffic mainly to car pools.
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.
In the late 1970s and early 1980s, the highway's final miles were built. A section from Delaplane to US 17 east of Marshall was completed in two sections in 1978 and 1979. The section from US 340 to Delaplane was completed in August 1979. A section between US 17 in Marshall and US 15 in
Haymarket opened in December 1979, with the gap between Haymarket and Gainesville closed on December 19, 1980. 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.
[
The Custis 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.] The Metrorail in the median of I-66 between Ballston 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.
On October 9, 1999, Public Law
Public law is the part of law that governs relations and affairs between legal persons and a government, between different institutions within a state, between different branches of governments, as well as relationships between persons that ...
106-69 transferred from the federal government to the Commonwealth of Virginia
Virginia, officially the Commonwealth of Virginia, is a U.S. state, state in the Southeastern United States, Southeastern and Mid-Atlantic (United States), Mid-Atlantic regions of the United States between the East Coast of the United States ...
the authority for the operation, maintenance, and construction of I-66 between Rosslyn and the Capital Beltway.
Because I-66 is the only Interstate Highway traveling west from Washington, D.C., into Northern Virginia
Northern Virginia, locally referred to as NOVA or NoVA, comprises several County (United States), counties and independent city (United States), independent cities in the Commonwealth (U.S. state), Commonwealth of Virginia in the United States. ...
, 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.). 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 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 shoulder lane can carry emergency vehicles and can be used in emergency situations. The second one widened between the Washington Boulevard onramp and the ramp to the Dulles Access Road. Work on it began in 2013 and finished in 2015. The third project, between Lee Highway/ Spout Run and Glebe Road, was completed in 2022.
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 one collector–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 with SR 619 (Linton Hall Road). The project began in 2004 and finished in 2015.
Transform 66
The Virginia Department of Transportation announced its public-private partnership with the Virginia Department of Rail and Public Transportation
The Virginia Department of Rail and Public Transportation (VDRPT) is an agency of the Commonwealth of Virginia in the United States. The agency's mission is "to connect and improve the quality of life for all Virginians with innovative transpor ...
, 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.
=Timeline
=
In 2015, the Virginia Department of Transportation planning board added I-66 HOT lanes to their list of priority projects for the I-66 corridor. 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 and Chambers of Commerce located near the affected areas, however, supported the improvements.
Residents along the I-66 corridor, such as in Arlington County, have resisted I-66 widening proposals for many years. The local Stenwood Elementary School would lose its attached field, leaving it with blacktop-only recess space. 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 include National 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, 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.
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 of I-66 between US 29 in Rosslyn and the Capital Beltway to an HOV variable congestion 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.
VDOT designed the price of toll to keep traffic moving at a minimum of 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. 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 versus a year before. 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.
In 2017, construction began on the "Transform 66 Outside the Beltway" improvement project. The project added 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 of expanded multi-use trail. The project was completed in November 2022.
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 and Fairfax Drive (exit 71) in Ballston, and provided a new ramp-to-ramp direct access connection from eastbound I-66 to the West Falls Church station at the SR 7 interchange and provided a new bridge for the W&OD Trail over US 29.
VDOT completed in August 2018 a diverging diamond interchange in Haymarket at the interchange of I-66 with US 15.
Washington, D.C.
In Washington D.C., I-66 was planned to extend east of its current terminus along the North Leg of the Inner Loop freeway. I-66 would have also met the eastern terminus of the planned I-266 at US 29, and the western terminus of I-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 six-lane tunnel beneath K Street, between I-266/US 29 and New York Avenue, where the North Leg would emerge from the tunnel and join with the Center Leg Freeway (formerly I-95, now I-395); the two routes would run concurrently for before reaching the Washington 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.
66 Parallel Trail
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 in Dunn Loring to a point just west of Rt. 28 in Centreville. 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.
Exit list
All exits in the District of Columbia are unnumbered.
Cancelled auxiliary route
Interstate 266 (I-266) was a proposed loop route of I-66 between Washington, D.C., and Arlington County, Virginia
Arlington County, or simply Arlington, is a County (United States), county in the U.S. state of Virginia. The county is located in Northern Virginia on the southwestern bank of the Potomac River directly across from Washington, D.C., the nati ...
. D.C. officials proposed designating the route Interstate 66N, a move opposed by AASHTO
The American Association of State Highway and Transportation Officials (AASHTO) is a standards setting body which publishes specifications, test quality control, protocols, and guidelines that are used in highway design and construction through ...
. In Virginia, I-266 would have split off from I-66 just east of the present SR 124 (Spout Run Parkway) exit. From there, it would have followed an expanded Spout Run Parkway, crossed the George Washington Memorial Parkway, and crossed the Potomac River
The Potomac River () is in the Mid-Atlantic (United States), Mid-Atlantic region of the United States and flows from the Potomac Highlands in West Virginia to Chesapeake Bay in Maryland. It is long,U.S. Geological Survey. National Hydrography D ...
across a new bridge that would have been called the Three Sisters Bridge. Upon entering D.C., it would have followed Canal Road and an expanded US 29 (Whitehurst Freeway) to rejoin I-66 at K Street. I-266 was canceled in 1972 in the face of community opposition during Washington, D.C.'s freeway revolts.It also would've been the only auxiliary route of I-66.
References
External links
Transform 66 Outside the Beltway Project
HOV schedule in Northern Virginia, from Virginia Dept. of Transportation
Steve Anderson's DCRoads.net: Interstate 66 (Virginia)
{{Authority control
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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
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