One day someone is going to make ten million bucks by patenting a way of determining a persons current performance capabilities, and comparing it to their historical average.
I don't know if it will be an app that sits on the work computer desktop, or similar to a sony virtual reality headset gizmo, or a thumb prick like when a diabetic tests for glucose levels, or what form it will take. But when it is invented it will cover fatigue, drugs, alcahol, the flu, you name it, if you can't perform within cooee of your normal ability it will ping. If that ocurrs at the start of the roster you won't be allowed to sign on, if it ocurrs at sign off you'l be stood down for 24 hours.
I don't fully believe that this will happen in my lifetime but if it did, (never say never)I'd wager the decrease in accidents would compare to the advent of EGPWS.