I recently had dinner at Timbre+ in Ayer Rajah Crescent and was impressed with the cleanliness of the establishment.
It is styled like a hawker centre with a number of individual stalls.
You simply order your food and collect your meal on a tray, all self-service.
An additional charge of $1 is imposed, on top of the cost of the food (Charge nominal fee for trays at hawker centres, by Mr Damian Ng Swee Beng; Sept 19).
When a person finishes eating, he simply returns the tray on a conveyor belt at a tray collection area and the dollar is returned through the machine.
There are two cleaners whose duty is to wipe up any spills on the tables. No additional staff is needed.
It is true that years of appeals and education have done little to entice diners to return their trays after their meals.
Where persuasion and other methods have not produced the desired outcome, the one implemented by Timber+ is worth considering.