Every night, 1,200 trailers would cross those docks. The SAIA DDC’s Programmable Logic Controllers (PLCs) ran a relentless ballet: a trailer backs in, the DDC senses the proximity switch, lowers the leveler, unlocks the overhead door, and signals the forklift dispatcher that a new slot is ready. It was a symphony of industrial automation, written in SAIA’s proprietary PG5 software, and it had been playing perfectly for three years. It was December 19th, the peak of the holiday shipping surge. Marco was in his cubicle, sipping cold coffee, when the first alert flickered across his SCADA (Supervisory Control and Data Acquisition) dashboard—a custom SAIA web interface he’d built himself.
His finger hovered over the Download Changes button. saia ddc
He opened the PG5 project file and navigated to the function block controlling doors 45 through 55. The code was clean, written in SAIA’s FBD (Function Block Diagram). But one variable stood out: East_Air_Pressure . Every night, 1,200 trailers would cross those docks