In the event of an accident investigation tiredness would be difficult to prove unless there were witnesses to what someone was doing prior to a work shift.
I agree that someone who is excessively tired vs. someone who smoked a joint a few days prior is really no comparison. Trouble is, if it went to court the traces of marijuana would show in their system.
The new law is certainly going to present some interesting court challenges in the coming days. A lot of precedents will be set.
Trains are equipped with all kinds of safety protocols to prevent drivers from nodding off. The so called "dead man stick". If a driver falls asleep, the railway can often times find that out.
1. Trains have on board computers that require the driver to do something, anything, in a given period of time (say 30 seconds). So every 30 seconds, the driver must make a throttle adjustment, or a brake adjustment, or acknowledge a request. Something, orelse the locomotive will power down. It's pretty hard to nod off and get away with it. (This is the modern equivalent of the "deadman" which used to be a lever that the guy had to hold orelse the train would come to a stop. Problem was guys just propping the lever with a tool box and the whole fail-safe protocol was defeated.)
2. There are cameras all over the trains, including the cabs, cars, and the back end where the conductor will sit to control the train when it's going westbound, etc. If the system alarmed because the driver was not making commands, the camera would catch him nodding off.
3. Like a plane, a train has black boxes and it would record all relevant data, including conversations in the locomotive. (Like when that VIA train derailed in Burlington 10 years ago or so)
4. Rail Traffic control will know immediately if a train does something in contravention to its authority -
like blow through a red light.