The Custis Trail is a hilly 4.5 miles (7.2 km)-long shared use path in Arlington County, Virginia. The asphalt-paved trail travels along Interstate 66 (I-66) between Rosslyn and the Washington & Old Dominion Railroad Trail (W&OD Trail) at Bon Air Park.
The Custis Trail's eastern trailhead is at the trail's lowest elevation (33 feet / 10.1 m). The trail connects at the trailhead to the Mount Vernon Trail, which provides access to three Potomac River crossings into downtown Washington, D.C., and the National Mall:
Theodore Roosevelt Bridge
Arlington Memorial Bridge
George Mason Memorial Bridge (see 14th Street bridges)
250 yards (229 m) west of the trailhead, the Custis Trail connects at North Lynn Street to the Francis Scott Key Bridge, thus creating connections to Georgetown, to the southern end of the Capital Crescent Trail and to the Chesapeake and Ohio Canal towpath. The trail then follows a hilly route along I-66 through Arlington County until reaching its western trailhead at the trail's junction with the Washington & Old Dominion Railroad Trail (W&OD Trail) at Bon Air Park near Four Mile Run. The western trailhead is 75 yards (69 m) east of North Patrick Henry Drive's overpass of I-66, the W&OD Trail and Four Mile Run.
The trail reaches its highest elevation (299 feet / 91.1 m) near the North Harrison Street overpass of I-66 and the trail, west of Ballston. The trail descends from that high point to the western trailhead, whose elevation is 233 feet (71.0 m).
The Custis Trail crosses I-66 three times along its route:
Within the Lee Highway overpass west of Rosslyn.
Within the Lee Highway underpass west of Spout Run Parkway (Virginia State Route 124).
Within the Four Mile Run underpass near the trail's western trailhead.
The trail has five at-grade street crossings, all of which in a section of the trail that travels next to the westbound traffic lanes of Lee Highway in and near Rosslyn. After the trail crosses I-66 on the Lee Highway overpass west of Rosslyn, the trail travels next to I-66 and crosses all streets on the highway's underpasses and overpasses.
The trail has a 300-yard (274 m)-long spur that travels east to Fairfax Drive (Virginia State Route 237) along the westbound entrance ramp to I-66 in Ballston. The spur connects to Ballston's streets and to the Bluemont Junction Trail, a 1.3-mile (2.1 km)-long rail trail that meets the W&OD Trail and the Four Mile Run Trail at Bluemont Park.
