Alcohol and later drugs has been a serious problem in the railroad business up until the
1987 AMTRAK Crash, Chase, MD. Afterward the Engineer Ricky Gates went before Congress and testified how prevalent an issue this was. Soon afterward Congress mandated Drug & Alcohol testing for a railroad employees in safety sensitive positions.
There are a few that still try, but its become rare. Many railroads offer a "bypass" program, allowing an employee to turn himself or a peer in and allowing that person the opportunity for treatment. If you however are caught by Management, Federal law only allows you to get treatment once, then you are terminated after a second event. If you were to get hired by another railroad and caught yet again you can be barred from all railroads by the FRA for I believe 6 years.