Ed, I agree that opening the doors seems sensible in hot weather, especially under low-speed conditions. That is why I am surprised there aren't more pictures of locos in-service with open cab doors, especially switchers. Maybe most of the old published company locomotive pictures are staged, and the railfan ones are mostly outside yard limits, where doors might not be open due to speed or rules?
(Yes, I have been in a cab, and even shoveled some coal, and they let me blow the whistle for a grade crossing. But they did not let me get my hand on the throttle.)
