Woodie, years ago there was a "dead man switch" in some of the units, most likely F-3s etc. It was on the floor and the driver had to keep his foot on it all the time. As it turned out this was a great place to put your tool box or what ever would hold the thing down.
As I under stand it, if used properly, should something have happened to the driver, the release of the switch would cut the power and dump the air.
George has a good point, a one man crew would not be the best idea in one of these new cabs, but new cab or not, there should always be two persons.
About two or three years ago one railroad approached the State of Wisconsin in regards to one man crews and the state refused.
It was also state regulations as to the need for a caboose.
Lance