Adrian Miranda explains how he beats the Opal card system. "You tap on, tap off, and rinse, repeat," said Mr Zakharov. For those not in on it, the gambit, which is completely legal, works like this: Commuters travel for free on an Opal card after completing eight journeys in a week. The aim, therefore, is to ensure those eight journeys are short and cheap ones, rather than expensive peak hour train journeys or long bus trips.

Commuters use Pyrmont stops to beat the Opal card. And the two light rail stops at Pyrmont Bay and The Star, which are about 200 metres apart, are a perfect spot to accrue cheap $2.10 journeys, or $1.05 journeys for students. Between 11am and 12.15pm on Monday, Fairfax Media counted more than 150 instances of people tapping the Opal reader at Pyrmont Bay then walking away from the stop, clearly with no intention of catching a tram. Commuters use Pyrmont stops to beat the Opal card. Many did so once or twice. But others continued to shuttle back to the Opal reader until they had maxed out their Opal card for $15 for adult fares or $7.50 for student fares.

"You can do it in two hours if you're walking, or I think one hour and a half, one fifteen if you're running," said Mr Zakharov, who works in the city and makes up the time spent filling up his Opal card later in the week. Mr Zakharov said the shuttle saved him about $25 a week. Another shuttler, Inn Tan, said she saved $20 to $30 a week filling up her card at Pyrmont as opposed to her regular bus and train fares from Lidcombe. "You do this and you get the savings," said Ms Tan, maintaining a brisk pace after her sixth Opal "journey" for the morning. "More coffees, more beers if you like. Everybody should do it."

The Opal card has features which make it difficult to quickly tally cheap journeys. Each individual trip typically needs to be separated by an hour from the next or they would be counted together as just the one "journey". But there is a way around this. Four trips together automatically registers as one journey. This means that you can fill up an Opal card for $15 (the daily maximum) by walking - or skateboarding, jogging, or cycling - back and forth between The Star and Pyrmont Bay about 27 times, depending on how you travel there. "It's also a really good way to exercise, I guess, every Monday morning," said Adrian Miranda, a maths student at the University of NSW.

"In total, you've walked just under six kilometres, which is not bad for your health," said Mr Miranda. A Central Coast resident was cycling between the two light rail stops. Paul, who did not want to give his last name, estimated he saved between $38 and $45 through his bike shuttle. "Previously I had an annual ticket, but they just don't offer that in the new system," said Paul. "If they did that [the annual ticket] I would use that." The former NSW Transport Minister, Gladys Berejiklian, last year encouraged commuters to "beat the system" and "find the savings" in the Opal card. And the new Transport Minister, Andrew Constance, seemed similarly nonplussed when asked about the Pyrmont shuttle.

"Customers are welcome to use public transport as often as they want or need," said a spokesman for Transport for NSW. "It would be a difficult and time-consuming task to max out your Opal card by walking or jogging between The Star and Pyrmont Bay light rail stops and the average customer would find it completely unnecessary," the spokesman said. Which is perhaps fortunate, lest the footpath outside the tram stop gets too overcrowded. jsaulwick@smh.com.au