Interstate 66 Main route of the Interstate Highway System
Length:	76.2 mi[1] (122.63 km)
West end:	I-81 in Middletown, VA
Major junctions:	US 15 in Haymarket, VA US 50 near Fairfax, VA I-495 near Vienna, VA SR 267 near Falls Church, VA
East end:	US 29 in Washington, D.C.
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Interstate 66 (I-66) is an interstate highway in the eastern United States. As indicated by its even route number, it runs in an east-west direction. Its western terminus is at Middletown, Virginia, at an intersection with Interstate 81;^[2] its eastern terminus is in Washington, D.C., at an intersection with U.S. Route 29.^[3] Interstate 66 has no physical nor historical connection to U.S. Route 66.

Route description

I-66's western terminus, where it splits from I-81

Virginia

Rush hour traffic on I-66 westbound heading into Prince William County

Because I-66 is the only major highway running west from Washington, D.C., into Northern Virginia, traffic on the road is often extremely heavy. For decades, there has been talk of widening I-66 from 2 to 3 lanes each way inside the Capital Beltway (Interstate 495) through Arlington, Virginia, although many Arlington residents are adamantly opposed to this plan. The Virginia Department of Transportation (VDOT) is studying the prospect of implementing this one-lane extension on westbound I-66 within the Beltway (thus alleviating congestion for people commuting away from DC).^[4]

Due to heavy commuter traffic, I-66 features high-occupancy vehicle (HOV) lanes in varying degrees. Between the Prince William Parkway (State Route 234) in Gainesville, Virginia and the Beltway, the left lane on eastbound I-66 is reserved for HOV-2 during morning rush hour (5:30 a.m. to 9:30 a.m.), and the left lane on westbound I-66 is reserved for HOV-2 during evening rush hour (3:00 p.m. to 7:00 p.m.). Also during those rush hours, between U.S. 50 and the Beltway, the right-hand shoulder is available for use as a travel lane.^[5] Within the Beltway (between the Beltway and the Theodore Roosevelt Bridge), the entire eastbound (inbound) roadway is reserved for HOV-2 and Washington Dulles International Airport traffic during morning rush hour (6:30 a.m. to 9:00 a.m.), and the entire westbound (outbound) roadway is reserved for HOV-2 and Dulles Airport traffic during evening rush hour (4:00 p.m. to 6:30 p.m.). This is not readily and easily enforced, since single-passenger vehicles are allowed to come onto the highway within the beltway in the direction of rush-hour traffic when they are intending to use the Dulles toll road at exit 67.

Between Vienna and western Arlington County, the Orange Line of the Washington Metro runs along the median of the interstate. Four stations (Vienna/Fairfax-GMU, Dunn Loring-Merrifield, West Falls Church, and East Falls Church) are located along this section.

I-66 east has two exits, one from each side of the carriageway, to the Inner Loop of I-495. One is a right exit, while one is a left exit; the latter is retained to make it easier for traffic to join the Inner Loop without having to weave across the entire carriageway. Also, there is no access from the Outer Loop of I-495 to I-66 east; traffic wishing to make this movement must use State Route 267 east.

I-66 is named the "Custis Memorial Parkway" east of the Capital Beltway in Virginia. The 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's history.

District of Columbia

In Washington D.C., I-66 follows the West Leg of the Inner Loop freeway. After crossing the Potomac River on the Theodore Roosevelt Bridge concurrent with US 50, the route quickly turns north, separating from US 50. The Interstate interchanges with E Street before passing beneath Virginia Avenue in a short tunnel. It then interchanges with the Rock Creek Parkway (via 27th Street NW and Virginia Avenue NW) and Pennsylvania Avenue. The route ends at US 29 and 27th Street, where it interchanges with the Whitehurst Freeway.

This is the only 2 digit Interstate to enter the District of Columbia (other than the 100 yards (100 m) or so that I-95 passes through DC on the Woodrow Wilson Bridge).

Major intersections

• Interstate 81 in Middletown, Virginia
• Interstate 495, the Capital Beltway at Falls Church, Virginia

History

Virginia

Interstate 66 in Fairfax County outside of the Capital Beltway, with the Metrorail Orange Line in the median. The left lane is HOV, and the right shoulder is used as a travel lane during rush hour.

As with many urban interstate highway projects, I-66 has encountered opposition from local citizen groups.

Most notably for I-66 was the construction through Arlington, Virginia, proposed in 1956. After the Virginia Department of Transportation (VDOT) (then known as the Virginia Department of Highways) acquired two sections of the former route of the Washington and Old Dominion Railroad to provide a right-of-way through Arlington for the new highway, the Arlington Coalition on Transportation (ACT) filed a lawsuit in Federal District Court in 1971 opposing the Arlington portion of the project. The group objected to that urban segment due to concerns over air quality, noise and community cohesion changes. In 1972 the U.S. Fourth Circuit Court of Appeals ruled in favor of ACT, technically blocking any construction. The U.S. Supreme Court upheld the ruling in favor of ACT later in 1972.^[6]

The impasse was eventually broken when the parties agreed on experts to conduct air quality and noise studies for VDOT; the firm of ESL Inc., the expert hired originally by ACT, was agreed upon to be hired by VDOT. Then, U.S. Secretary of Transportation Coleman personally intervened in 1976 with negotiations to reach a compromise of a reduced highway width including a transit element.^[7][8]

Less controversial was the portion of the highway's route immediately west of Arlington. There, VDOT decided to curve the highway to bypass the City of Falls Church, increasing the interstate's length while sparing the city from the road's immediate environmental impacts.

District of Columbia

A map of I-66, showing cities and intersections with other interstates.

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 Interstate 266 at US 29, and the western terminus of the South Leg Freeway (I-695) 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, as published in 1971, outlined a 1.5-mile (2.4 km) 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 3/4 of a mile before reaching the 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 vitriolic opposition to previous, scrapped alignments for the D.C. freeway network, which included previous alignments for the North Leg Freeway, led to the mass cancellation of all unbuilt D.C. freeways in 1977, resulting in the truncation of I-66 at US 29.

No auxiliary routes were constructed. Interstate 266 was planned in northern Virginia and Washington, D.C. It was cancelled in 1972 due to community opposition and environmental concerns.

Exit list

This section contains a table that is missing mileposts for one or more junctions. Please help by adding the missing mileposts.

County	Location	Mile	#	Destinations	Notes
Frederick	Middletown		1	I-81 – Winchester, Roanoke	Westbound exit and eastbound entrance
Warren	Front Royal		6	US 340 / US 522 – Winchester, Front Royal
			13	SR 79 to SR 55 – Linden
Fauquier			18	Image:Virginia 688.svg SR 688
			23	US 17 north / SR 55 west – Delaplane, Paris	West end of US 17/SR 55 overlap
	Marshall		27	Image:Virginia 647.svg SR 55 east / SR 647 – Marshall	East end of SR 55 overlap
			28	US 17 south – Warrenton, Fredericksburg	East end of US 17 overlap
	The Plains		31	SR 245 / Old Tavern Road
Prince William	Haymarket		40	US 15 – Leesburg, Haymarket
			43	US 29 – Gainesville, Charlottesville
			44	SR 234 south (Prince William Parkway)	West end of SR 234 overlap
			47	SR 234 north / SR 234 Bus. (Sudely Road) – Manassas	East end of SR 234 overlap
Fairfax			52	US 29 to SR 28 south – Centreville
			53	SR 28 north (Sully Road) – Dulles Airport
			55	SR 7100 (Fairfax County Parkway) – Springfield, Reston, Herndon
			57	US 50 – Winchester, Fairfax, Fair Oaks
	Fairfax		60	SR 123 – Fairfax, Vienna
	Vienna		62	SR 243 (Nutley Street) – Fairfax, Vienna
			64	I-495 (Capital Beltway) – Richmond, Baltimore	Left and right exit eastbound (left from HOV lane); no westbound exit to I-495 north
			66	SR 7 (Leesburg Pike) – Falls Church
			67	SR 267 to I-495 north / to Dulles Toll Road – Dulles Airport	Westbound exit only
Arlington			68	Westmoreland Street	Eastbound exit only
			69	US 29 (Lee Highway) / SR 237 (Washington Boulevard) / Sycamore Street
			71	SR 120 (Glebe Road) / SR 237 (Fairfax Drive)	Eastbound exit only
			72	US 29 (Lee Highway) / Spout Run Parkway	Eastbound exit only
			73	US 29 (Key Bridge) – Rosslyn
			75	SR 110 south – Pentagon, Alexandria, Pentagon City, Crystal City	Eastbound exit only
				US 50 west / Arlington Boulevard, George Washington Memorial Parkway	West end of US 50 overlap; westbound exit and eastbound entrance
Virginia – District of Columbia state line
Washington				Independence Avenue
				US 50 east / Constitution Avenue – Downtown	East end of US 50 overlap; eastbound exit and westbound entrance
				E Street Expressway
				Rock Creek Parkway	Eastbound exit and westbound entrance
				Pennsylvania Avenue	Eastbound exit and westbound entrance
				US 29 south / Whitehurst Freeway, Canal Road	Eastbound exit and westbound entrance
				M street NW	At-Grade Intersection

Auxiliary routes

v • d • e Auxiliary routes of Interstate 66 Virginia-District of Columbia: 266 (unbuilt)

References

External links

• HOV schedule in Northern Virginia, from Virginia Dept. of Transportation
• December 22, 1982 Completion of I-66, from AASHTO
• This Day In Interstate Highway System History, from AASHTO
• Roads to the Future: Washington D.C. Interstates and Freeways

Main Interstate Highways (multiples of 5 in pink)
4	5	8	10	12	15	16	17	19	20	22	24	25	26	27	29	30
35	37	39	40	43	44	45	49	55	57	59	64	65	66	68	69
70	71	72	73	74	75	76 (W)		76 (E)		77	78	79	80	81	82
83	84 (W)		84 (E)		85	86 (W)		86 (E)		87	88 (W)		88 (E)		89	90
91	93	94	95	96	97	99	(238)		H-1		H-2		H-3
Unsigned			A-1		A-2		A-3		A-4		PRI-1		PRI-2		PRI-3
Lists		Primary			Main - Intrastate - Suffixed - Future - Gaps
		Auxiliary			Main - Future - Unsigned
		Other			Standards - Business - Bypassed

Browse numbered routes
< SR 65	VA		SR 67 >
< US 50	DC		I-95 >