[1] The remaining portions of the Shirley Highway south to U.S. Route 1 in Colchester, just north of Woodbridge, were completed in 1952.

The original interchange had a merge section each way, about 1/3 mile long, with a third "mixing lane" where the vehicles would weave when they wanted to change to the other freeway.

This project led to the purchase and demolition of the Twin Bridges Hot Shoppes Restaurant and the closure of the Washington & Old Dominion Railroad - the latter of which delayed the widening of the highway while a fight over its abandonment was resolved.

The remaining portion of the Shirley Highway north of Springfield was redesignated Interstate 395, which continues into D.C. to its end at U.S. Route 50 (New York Avenue).

On September 22, 1969, the reversible roadway between Edsall Road and SR 7 was converted to the first separated bus rapid transit (BRT) route on an Interstate highway during peak morning commute hours (0630–0930); this was extended north to Shirlington the next day.

[3]: 9  The busway was extended to north of Glebe Road in September 1970, and then to the new Center Span Bridge on April 5, 1971.