CSX Replaces One of Nation's Most Complex Rail Crossings

CSX recently completed a highly complex replacement of the Darby Diamond in Pennsylvania — a rare intersection where a freight rail line, a four-lane highway, and two mass-transit tracks all meet at the same level.

This crossing is among the most challenging in the nation to maintain, due to its unique mix of traffic and the differing track gauges used by CSX and SEPTA, the local transit authority. It is the only location where a Class I railroad intersects a four-lane roadway and two mass-transit lines at grade within a single intersection. To complicate matters further, SEPTA operates on Pennsylvania gauge while CSX uses standard gauge, requiring a flange-bearing crossing for trolley operations.

The replacement project, which began on October 29, involved removing aging components and installing a new diamond supported by concrete panels. Executing the work demanded precise, round-the-clock coordination among CSX, SEPTA, the Borough of Darby, and the State of Pennsylvania. Traffic detours helped minimize disruption for commuters throughout the construction window.

Because of its complexity and heavy usage, the Darby Diamond typically requires replacement every five to seven years. The successful, on-schedule completion of this year’s project highlights the CSX Engineering team’s meticulous planning, strong collaboration, and ongoing commitment to safe and reliable operations.