I searched a bit and found that "Trolley Assist" apparently refers to a system where large diesel-electric mining trucks use overhead lines for part of their jo

I searched a bit and found that "Trolley Assist" apparently refers to a system where large diesel-electric mining trucks use overhead lines for part of their journey. (You can do an image search for "trolley assist" and find examples.) I guess this is the kind of thing I was looking for.