Interstate 66 is a relatively short but strategically significant east–west Interstate Highway that connects the heart of Washington, D.C., to northern Virginia. Stretching approximately 76 miles, I-66 begins at the western edge of the nation’s capital and extends westward to Interstate 81 near Strasburg, Virginia. Despite its modest length, the corridor plays a vital role in regional commuting and freight movement, especially as a primary access route into the D.C. metro area from the west.

The route is unique in that it combines elements of an urban expressway, suburban commuter route, and rural connector. East of I-495 (the Capital Beltway), I-66 is subject to HOV and toll lane restrictions, dynamically priced to manage congestion and encourage carpooling. In contrast, the western segments offer more traditional freeway characteristics through the Shenandoah Valley and the edge of the Blue Ridge Mountains. This combination of high-density traffic control and scenic surroundings sets I-66 apart from many other Interstate routes.

Over the years, I-66 has undergone major expansions and modernization projects, most notably the Transform 66 Outside the Beltway initiative. This public-private partnership project added express lanes, rebuilt interchanges, and improved transit and bike infrastructure to better serve the growing Northern Virginia population. With its evolving infrastructure and proximity to political, economic, and historical centers, Interstate 66 remains one of the most monitored and modernized highways in the eastern United States.