The kind act of the MRT employee who topped up the ez-link card of the student who did not have enough money, while heart-warming, also highlights a problem (MRT worker used own money to help; May 12).

The current system does not allow you to go pass the fare gates unless your card balance is high enough.

In the Shanghai Metro, as long as your card has a positive balance, you can enter the fare gates even if, when you eventually exit, the card ends up with a negative balance.

The outstanding amount will be paid when the card is topped up again.

As someone who has also been caught out by this weakness in the MRT system here, I urge the authorities to make the necessary adjustment to the turnstiles to allow access as long as one's ez-link card has a positive balance.

Duncan Urquhart