Technology-driven solutions to the problem of missing trolleys would incur high costs, which will eventually be passed on to consumers ("Install tracking devices in trolleys" by Dr V. Subramaniam; Monday).

Instead, the problem can be solved by having security personnel at the exit points of supermarkets and shopping malls to stop shoppers from taking the trolleys away.

If the supermarket chooses to allow shoppers to take the trolleys and return them later, the shopper's identity should be recorded and a gate pass issued.

Such shoppers would be obligated to return the trolley or face penalties.

On another note, using technology to see when bins are full is a great idea ("Trash tech"; Monday).

Now, these smart bins can be found only in public places and strategic locations such as community centres, the Singapore Sports Hub, airport and bus interchanges.

Perhaps, over time, the cost of smart bins will come down and their use can be widespread.

Having a smarter way of trash collection and disposal is indeed a sign of a "smart nation".

Pradip Mandal