BNSF 7601 works as the lone DP locomotive on the rear of the Stockton, CA to Willow Springs, IL Z-train. Though this train is light and short, Union Pacific train makeup rules for Tehachapi Pass prohibit the use of more than three locomotives on the headend consist for southbound trains. As a result, BNSF runs their Z-STOWSP in a 3x1 configuration to keep it within the scheduled HPT requirements.