@mattiasrikka They are used to power (via charged batteries) the automated dumping on the cars and GPS coordinates are used to dump the rock where needed along the rail line.
Walking through flood waters of Mississippi River
GPS power ballast train running along Mississippi River
Stacks at sunrise. UP Geneva sub.
YBE51 11 crosses the Rock River
Powerton coal running along Rock River
UP Geneva sub passing old CNW depot
Entering the Villa Grove sub.
Two SD60's notched out pulling a grain train over the grade.
A loaded iron ore train gliding downgrade in full dynamics.
A loaded coal train climbing a stiff grade.