The Saw Mill Run Boulevard section of the highway was the first direct connection between Pittsburgh and the South Hills once the Liberty Tunnel was completed. It significantly decreased the driving time to Pittsburgh from the cities of Clairton, Duquesne, McKeesport. Improvements are planned at the intersection with PA 88 south of Pittsburgh, where bottlenecks occur regularly. Other improvements planned include new interchanges at the Liberty Tunnel and West End Bridge (West End Circle), a center median for the rest of Saw Mill Run Boulevard, and an improved intersection with Woodruff Street. Saw Mill Run Expressway (canceled) The Saw Mill Run Expressway was a highway proposed for the South Hills. It would have been built on the same right-of-way as Saw Mill Run Boulevard. In 1964, while designated as "the worst bottleneck in Western Pennsylvania," a plan was made to turn the crowded highway into an expressway. The plan was proposed to the Department of Highways and included a renovation of the Liberty Tunnel, several widening projects, new turning lanes, and a central median. The plan would have required cooperation from the surrounding communities. The finished product was to include a limited access expressway from Overbrook to the West End. It would have been twice the width of the current highway and had a total cost of nearly $150 million. Interest in the expressway declined once the Southwestern Pennsylvania Regional Planning Commission expressed concerns about business along the corridor, and the project was dropped in 1973. Major intersections Related routes Pittsburgh truck route Pennsylvania Route 51 Truck (PA 51 Truck) is a truck route along major roads in downtown Pittsburgh, such as I-376, I-279, and I-579, in an effort to bypass PA 51, which features some unsafe S-Curves and falling rocks that could be deleterious for trucks. Motorists traveling on PA 51 should use PA 51 Truck to travel downtown and avoid these dangers. Elizabeth truck route Pennsylvania Route 51 Truck (PA 51 Truck) was a truck route of PA 51 that bypassed the weight-restricted Regis R. Malady Bridge over the Monongahela River between Elizabeth and West Elizabeth, on which trucks over 32 tons and combination loads over 40 tons are prohibited. The route followed McKeesport Road, Lincoln Boulevard, Glassport-Elizabeth Road, the Clairton-Glassport Bridge over the Monongahela River, and PA 837. The route was formed in 2013; however, as of 2021, there were no weight restrictions listed on the bridge