US 13 split from US 422 by turning northeast onto Frankford Avenue, running concurrent with PA 73 between Levick Street and Cottman Avenue. In addition, a bypass route known as US 13 Byp. was created, bypassing the central part of Philadelphia to the north and west. By 1950, two bypass routes were designated for US 13 in Delaware County. The first US 13 Byp. bypassed the portion between Marcus Hook and Chester while the second US 13 Byp. served as a bypass of the portion of the route that followed Chester Pike between Chester and Darby. US 13 was realigned to a new divided highway alignment of Bristol Pike between PA 413 in Bristol and Tullytown by 1950, having previously followed what is now Old Route 13, Pond Street, Farragut Avenue, Radcliffe Street, Main Street, and Fallsington Avenue between the two boroughs. In 1954, the US 13 freeway was built between Tyburn Road and US 1. A year later, the freeway was completed between Tullytown and Tyburn Road, at which point US 13 was rerouted to follow the freeway to US 1. The US 13 freeway was planned to be incorporated into I-95, which would head northeast from its current routing at PA 413 and continue along the US 13 alignment to US 1, where it would follow that route across the Delaware River on the Trenton–Morrisville Toll Bridge and through Trenton, New Jersey. However, this plan was opposed by New Jersey officials and I-95 was instead routed to bypass Trenton to the north, crossing the Delaware River on the Scudder Falls Bridge. Plans resurfaced for an extension of the US 13 freeway in 1969 that would run from I-95 at the PA 413 interchange northeast to the south end of the current freeway in Tullytown, interchanging with the Pennsylvania Turnpike. This freeway was projected to cost $12.5 million. This freeway, which would have provided a missing connection between I-95 and the turnpike, was never built because it would have impacted Silver Lake Park. In the 1950s, US 13 was shifted in Philadelphia to run along the one-way pair of 43rd Street northbound and 44th Street southbound from Baltimore Avenue, Powelton Avenue, 34th Street, Girard Avenue (where it ran concurrent with US 30), 33rd Street, Ridge Avenue, and Hunting Park Avenue (where it ran concurrent with US 1) to Roosevelt Boulevard. The US 1 concurrency south of Hunting Park Avenue was removed, with US 1 shifted to an alignment further to the west concurrent with US 13 Byp.