 PA 33 begins at a trumpet interchange with I-78 in Lower Saucon Township in Northampton County, which is in the Lehigh Valley.From this interchange, the route heads northwest as a four-lane freeway and heads onto the Gene Hartzell Memorial Bridge, passing over Norfolk Southern's Lehigh Line and the Lehigh River, where the highway briefly cuts through the southwestern tip of the city of Easton before crossing the Lehigh Canal into Bethlehem Township.Past the bridge, the freeway passes farm fields before it comes to a partial cloverleaf interchange with Freemansburg Avenue in a business area adjacent to St. Luke's Hospital-Anderson Campus.