Returning trolleys at supermarkets and returning trays at food centres have one thing in common - they are part of efforts to cultivate graciousness and courtesy so that other people will be able to use these facilities without being inconvenienced ("Supermarket trolleys left for months in condo carpark"; July 19).

Supermarket staff have to work longer hours to retrieve abandoned trolleys. Lost trolleys have to be replaced, increasing costs for supermarkets and food prices for consumers.

Supermarkets should place an advisory at the front of the trolleys, warning that users who do not return them will be fined. This will send a strong deterrent message on the unauthorised use and theft of trolleys.

The long-term solution would be to install security alarms and trackers on supermarket trolleys. If a trolley were to go outside a designated area, the alarm would go off and the only way to stop the alarm is to return the trolley.

Another method would be to install automated locks on the wheels or to ask shoppers to exchange their identity card for a trolley.

Supermarkets have spent much effort educating users to make returning trolleys a social norm, and to inculcate gracious behaviour in respecting public property and allowing others to use the trolleys.

But if users still refuse to comply, then the hard approach - legislation - may be necessary.

I hope that everyone can make responsible and gracious use of trolleys, as they form a complimentary service that should not be taken for granted.

Darren Chan Keng Leong