The Arlington Triangle is exactly what its name suggests: a triangular-shaped route that connects together a slice of northeast Arlington, Virginia. Completed as a circuit, the route runs just over 16.5 miles in total, combining segments of the Custis, Mount Vernon, Four Mile Run, and W&OD trails. The Triangle route is entirely paved and is well-maintained. The route is also mostly flat, with the exception of the section of the Custis Trail that runs from Rosslyn, VA to its natural intersection with the W&OD trail just southwest of Westover Park. The Custis Trail is hilly in both directions, and in the summer months, it can be quite exposed. Runners should plan—and time—their circuit loops accordingly.
One of the great advantages of the Arlington Triangle is that the majority of it is entirely separated from highway and neighborhood traffic. Runners should be prepared for at-grade street crossings when switching from the Four Mile Run Trail to the W&OD just outside of Shirlington, VA (there is also a major at-grade intersection where the W&OD crosses Columbia Pike). Similarly, runners should proceed with caution though the Rosslyn segment of the Custis Trail, which runs on the sidewalk for Route 29/Lee Highway and contains a cluster of at-grade intersections with neighborhood cross streets. Otherwise, the trail offers runners a prime opportunity to practice pacing and to enjoy some quieter and more wooded parts of Arlington County.