Thirty seconds is a rather long period in a supposedly fail-safe system. I wonder if people are confusing devices designed to maintain concentration and alertness with tradition "dead man's switch" devices. Pressing a button every thirty seconds or so will not prevent disasters occurring during the thirty second period.
On many railway systems the driver has to maintain a constant pressure on a lever to prevent emergency brakes being applied. I believed that this was present in Underground trains. When I was much younger than I am now, I frequently travelled in a diesel multiple unit train running between Grantham and Nottingham. I liked to sit in the front coach and see the driver and the track ahead. On one occasion I recall the driver reaching for a leather shoulder bag, hanging it on the control lever then getting up and walking to his jacket that was hanging from a hook on the other side of the cab. He took something from his pocket and returned to his seat and then removed the bag and carried on as normal.
I suspect this behaviour was routine amongst drivers.
The paradox now is that it is entirely feasible to have totally automatic rail operation which may well be inherently safer than human operated systems. Such systems are likely to be perceived negatively by the general public who require the reassurance of a human operator.
