ICC Safety????

I was womdering when safety issues on RR's were brought to a national orginsation level? In other words I would like to see us put some time of time line together on when and why safety issues concerning both locomotives, passenger cars, and frieght cars were iniciated and how those implmentations effected the narrowguage. I know that alot of what we see in history concerning passenger cars and locomotives were both from state and national laws (Ie the legislatures and congress) but what other orginzations (regulatory) like the ICC set things in motion that effected the building and production and phisical charictaristics of the equipment. How about Union's, or fraternal orginisations?
I know there has been discussion on brake systems, boilers, and couplers in the past on this board.
Specifically, I have always wondered how the Uintah managed to have in operation a couple of water cars with a walk way that suspended between two water tanks that were installed on either end of a flat car. It looked dangerous, just sitting still, but I can not imagine trying to walk across it while the train was moving. They disapeared in the late teens, mostly because of new steel tank cars, but I was wondering if there was some other requirment at the time that motivated management to replace them other than they were old....