What's the date on this? Handheld/chest packs didn't start coming into general use until the mid-late 1970s.
I can't give you a qualified "this is what they're doing" answer, but I can share a few observations based on my experiences in railroading, and then I can make some assumptions:
* They're going fast enough that the guy on the point may be holding his billed hat in place. (Speed increases stopping distance.)
* IF they are descending a grade, and the Engineer already has them in "Full Service", they're in a precarious situation. ("Full Service" is about a 27 lb reduction.) IF they are slowing w/dynamics engaged, then he can work his dynamics (back then dynamics weren't as effective as today's dynamics, too) to a controlled stop at the signal the caption states the head end guy is watching for. Otherwise, if with Full Service and full dynamics they're only holding speed, then the next step for having a hope of stopping is "Emergency". A tidbit: IF one is in "Full Service" and it turns out to be too much air (and the train is going to eventually slow to a stop)... you'd best let it stop, secure the train, THEN release to recharge the air line sufficiently before kicking off a 27 lb reduction and proceeding. A 27 lb reduction is a BIG reduction and the recovery time for the air line would be such that you could get yourself in a real pickle real quick by kicking off that much air on the roll while on a steep descent (with more descent ahead of you). SO, I highly doubt the train is in "Full Service". Brake shoes can smoke, even at lower reductions, no biggie.
* Running long hood forward on a main w/tight curves SUCKS. I have had times that I'm clicking along on main lines at the maximum allowable track speed (35 - 45 MPH depending), and when entering a right hand curve, there have been many times that I could not see the rail in front of me. IF one is approaching a signal, OR if you're running under "Restricted Speed", then the above vision issue is NOT satisfactory, period. In such a situation, the head end guy(s) will have to be my "eyes" to the right, calling out to me the signal indication. (OR track situation in enough time for me to finish stopping the train within half the distance of sight if needed when running under Restricted Speed.)
* I don't know if the lead engine is set up with dual controls, or whether it's one of those sure 'nuf "long hood forward" engines and the long hood end IS "Forward".
The above so, then I would only be safe to suspect the following:
* The train is NOT in Full Service, but that it IS within full control and the Hoghead knows what he's doing.
* The head end man is riding the point so he can get a visual on the signal in the place of the poor Engineer that is having to deal with that long hood. (He's positioned to see the signal coming into view long before the Engr.) The above only applies IF the engine is a short hood "Forward" engine AND there's a right hand curve leading to the signal.
FWIW: IF this engine IS equipped with single controls AND the long hood is "Forward", then the chap on the pilot would be best served to position himself on the opposite side so that arm/hand signals can be conveyed in addition to the radio instructions (IF that is a radio). IF the engine is a designated short hood "Forward" engine, then he's already positioned nicely to do that, for the Engineer is seated on the same side as he's standing.