However, the firm, Octopus Cards - which won last year's Enterprise Award - is not resting on its laurels. It has embarked on setting up similar networks overseas and finding new ways to get people to use the cards.

Overseas expansion started last year with the setting up of a nationwide transport payment system in the Netherlands. The firm has entered the tendering process for a system in Melbourne and expects opportunities in North America over the next 12 months.

'Internationally, we want to take some of our technology, our skills and experience into other countries. We can either supply technology or we can supply expertise or we can help people run their business,' said Octopus Cards chief executive Eric Tai Yung-muk.

However, economics make it difficult to enter the mainland. 'The major difficulty in China is that the value of transport ticketing is low,' Mr Tai said. 'In China, a bus fare is $1 whereas in Hong Kong our average fare is $6.50.'

In Hong Kong Octopus earns 1 per cent of every bus, boat and train fare settled with its cards. Such a system is not viable with the mainland's lower prices.

Even where the fares approach Hong Kong levels - such as on the Beijing subway, where a standard ticket costs three yuan - there is not enough volume to make the business viable. Many commuters take the bus - the cheaper option.

'In Hong Kong, we generate 8.5 million transactions per day but we would be unlikely to generate that many at the price structure in a Chinese city,' Mr Tai said.

Octopus is also furthering its earnings growth in Hong Kong by encouraging use of the cards. There are now 270 retail outlets that accept the cards and the company expects to see turnover in this area increase by more than 10 per cent. 'We don't occupy a large share of the [retail] market ... but again we will see double-digit growth in that market,' he said.

Octopus also hopes to get into contention for payment on other forms of transport, such as red minibuses and taxis, as well as tunnels. 'Those are the niches not filled by us yet and we would like to capture those,' Mr Tai said.

But there are obstacles. Octopus operates with fixed prices for specific journeys, such as those charged by the MTR and green minibuses. With red minibuses and taxis, fares and routes vary.

'They are not fixed route and not fixed price so that becomes a bit more complicated,' he said.

Meanwhile, road tunnels have an auto-toll system, which makes Octopus unnecessary.

Octopus has signed 19 banks up to its automatic add-value service, which enables a card's value to be replenished immediately from the holder's bank account. Removing concerns about the card running out of money has been a key objective for Octopus.

'All the major retail banks are now working with us on both the credit card and the bank account side to link up with the Octopus card so that whenever the card runs out of cash, there will be an automatic credit of $250 going into the card.'

The company has also launched an insurance scheme by which one phone call can cancel lost or stolen credit cards. The insurance scheme also covers hotel bills and return flights if the cards are lost abroad.

However, the success of Octopus has raised some issues about pricing. For example, the company has lost money on short-term cards used by tourists. The company only covers the costs of a card and its management after it has been used for $750 of transactions - a level most tourists do not reach.

To lower these costs, Octopus began issuing over the summer souvenir cards, depicting, for instance, the Festival of Lights firework display over Victoria Harbour, that they hope buyers will keep. The cards cost a non-refundable $70 each. Standard cards require a $50 deposit, which is refunded when the card is returned.