This last weekend, my family and I drove the flat, boring stretch between Phoenix and Tucson. I've done this trip many times in the past and we usually pass 4-5 freights either way. Thing is, the usual sight is to see the freight being pulled by 4 engines. This trip, almost all the trains we saw were being pulled by two and followed up by two pushers. Any idea why the change in protocol? Would this require two engineers (doubtful) or can everything be controlled from the front cab (I expect)?