It appears that the other day restored 'Big Boy' no. 4014 was out on the main line somewhere in Nebraska when it was called upon to assist a stalled freight train. There are various videos on YouTube, including for example this one:
Here there are clips from the same video with commentary from someone who appears to know what he's talking about.
Here there are clips from the same video with commentary from someone who appears to know what he's talking about.