CHEYENNE, Wyo. — This week the Union Pacific made a short run with 4-8-8-4 No. 4014 to test the new PTC system installed on the locomotive. While Big Boy has operated with a LeaPTC system since 2021, says a UP statement, the new equipment permits operation without support of a diesel locomotive.
The original PTC system installed on the world’s largest operating steam locomotive utilized the computer aboard the diesel locomotive. The new system, similar to that installed on CPKC No. 2816, is self-contained. Although the diesel locomotive is no longer needed for Big Boy to travel, it is not certain if the steam locomotive will be permitted to travel without such support. The diesel locomotive was also present for added braking capability.
Big Boy’s new PTC equipment travels in a cabinet on the side of its tender.
When No. 4014 made its restored debut in 2019, it did not carry PTC equipment. The FRA granted a waiver for the locomotive to operate in PTC territory even without the system. Big Boy became the first mainline steam locomotive with PTC after a 2021 installation of the equipment.
