The accident happened around 11:30 p.m. Tuesday when the driver of a tractor-trailer tried to merge from the westbound Schuylkill Expressway to eastbound I-676.
The truck jackknifed, causing the trailer portion to slam against the side barrier and split open.
The truck was carrying more than 1,000 boxes of Crisco cake shortening - a very greasy substance - hundreds of which splattered across the roadway, necessitating a massive cleanup from PennDOT crews.
The driver was not hurt but the truck was wedged under the bridge for several hours.
The highway was closed between 30th Street and the Vine Street Expressway for hours while crews sanded the roadway in an attempt to soak up the remaining shortening.
Cake shortening is meant to grease pans - not roads, after all. So, crews had their hands full trying to extract it from the surface... and the weather complicated matters.
Layer by layer PennDOT crews lifted the lard, eventually allowing one lane to open at 7:00 a.m. They settled on a mixture of cinder and fine stones to get better traction, since between the rain and the grease, other substances were not working.
All lanes were finally re-opened around 3:00 p.m.