Looking for solutions to problems that are not there. Given the volume of traffic I am surprised this is even a starter. If the goal is revenue, e.g. some paid for card that lets you skip the security checks that is a possibility. I doubt anyone can correctly verify identity of all passengers without impacting travel time. So even with a card it is security theater and more of a revenue generation scheme.
That is a trend. Ever been on one of China's subways or intercity trains? Scrutiny has increased over time, and the checks especially for intercity travel are near what one expects for a plane ride.<p>A thorough security system would also look into other data associated with the ticket buyer.<p>Somewhere in there is a privacy issue. How much info does the state need on a passenger to quantify risk, based on an intention to board a train or plane?