Although the Broad Street Line was originally planned in the 1920s to be a 4-track facility for its entire length (Fern Rock portal to Snyder), the tunnel was built with provision for 4 tracks only from the portal to just north of Lombard-South. At the time of opening, the outer 2 tracks were built along this length, whereas the inner 2 express tracks were built only in two sections, from the Fern Rock portal/shops to just south of Olney, and from Girard to their terminus just north of Lombard South. To close the gaps, the two inner express tracks were laid from Erie to Girard in 1959, and again from Olney to Erie in 1991.