"But I had to change my office timing to 9.20am," he said. There are thrifty commuters across the city, and there have been for some time. But the manner in which transport users shape their travel in response to price and other incentives can now be depicted numerically for the first time thanks to Sydney's growing pool of Opal card information. According to Transport for NSW's early analysis of Opal card data, there are 40 per cent more people who "tap on" at rail stations in the five minutes after 9am - when off-peak discounts start - compared to the five minutes before.

At Ashfield, this can mean saving the difference between a $4.20 peak trip to the city and a $2.96 off-peak fare. There's a similar trend in the early hours. In the five minutes before 7am, when peak-hour pricing starts, 33 per cent more people tap on than in the five minutes after. In the evening there's a 40 per cent increase in people tapping on in the five minutes after 6.30pm, when peak fares end, than in the minutes before. In London, where that city's Oyster card has been in place about a decade longer than the Opal, transport authorities say they are still finding new ways to use travel data to better plan services. And in Sydney, authorities suggest they are still coming to grips with the possibilities opened up by Opal card information.

"It's in the very early days of assessing Opal data but there are some exciting opportunities emerging," said the Transport Minister, Andrew Constance. "When the time is right it could help with time-tabling, and for the first time show how, when and where people interchange," said Mr Constance. Cheaper off-peak fares are available only on rail services. But Transport for NSW has also provided a list of the top 10 more popular trips, by origin and destination, taken using an Opal card.

The figures show, for instance, that four of the six busiest bus trips in Sydney are between Central and the University of NSW. This analysis would be gladly received by a government soon to embark on the difficult process of building a light rail line along that corridor. Other popular bus trips include the relatively short journeys between North Sydney and Wynyard, and between Central Station and the University of Sydney, which is currently lobbying for a new campus rail station as part of the government's plans for another line through the city. While the Eastern Suburbs line is not Sydney's busiest rail corridor, it nevertheless features heavily among the top Opal trips. Other rail lines in Sydney might carry more commuters, but eastern suburbs commuters congregate at fewer rail stations.

The figures also demonstrate the overwhelming popularity of the Manly ferry. And a light rail trip of a couple of hundred metres - between The Star to the Pyrmont Bay stop - emerges as the third and fourth most popular trip on Sydney's line. The majority of people making this "trip" are presumably walking between the two stops, trying to reach their weekly cap of eight paid Opal journeys with $2.10 trips. According to Mr Constance, the ultimate aim in the collection of Opal data is "to make the information anonymous but accessible, so the experts can use it reliably in the developments of apps that improve the transport system even more."

In the meantime, commuters will continue to work out tics in the system for themselves. "A really interesting fact that a lot of people don't know," said Mr Kedari, "is that if you tap in at 8.59am you also get the cheaper fare. "I have tested it."