Lyn Hall, project manager with Trolley Tracker, said residents were encouraged to report strays of participating store Woolworths, Big W, Target, Franklins, Dan Murphy's to a toll-free phone number, with the information sent in real time via SMS to the relevant trolley collection contractor.

People can also report a missing trolley online with everyone making a report going in the draw for one of the five $1000 monthly rewards.

Ms Hall said a shopping trolley can be imported from China at $89, ``but it's still a very valuable asset''.

She said research showed only two and a half per cent of people took a trolley - but trolleys are very visual.

``It's the same offenders all the time,'' she said.

``The people who take it have not thought through the process.''

Use a trolley to take your shopping home, she said, but at least bring it back.

``The collectors are aware of the hotspots,'' Ms Hall said, with some collectors travelling up to five kilometres to retrieve a trolley.

``If we could just somehow change that public behaviour...it would be unbelievable.''

They can be found around taxi ranks, but Lyn said she found abandoned trolleys at bus stops and stations a little more disconcerting, as goods have to be carried at the other end anyway.

She said they at Trolley Tracker tried to encourage people to use personal trolleys instead.

A Penrith Council spokesman said since the council held an ``abandoned trolley forum' in April with major supermarkets and Trolley Trackers, reports of stray trolleys had reduced significantly.

``Stray trolleys are a problem right across Australia,'' he said.

Ms Hall said reporting a trolley was a great way for residents to help improve their environment; the longer the trolley stayed out, the more likely it was going to end up damaged or in water.

Ms Hall said the coin lock system at supermarkets was effective in some places, useless in others: ``It's people who walk''.