The NSW government is closing a loophole in its Opal smartcard transit ticketing system that inspired a movement of “runners” to earn unlimited travel for $18 a week – and half that price for students.

After an extended period of vague indifference to the practice, the state government twigged to the potential “millions of dollars each year” in fares it was doing without by not closing the loophole.

The loophole is in the way the Opal card fares are structured. Essentially free travel is earned after completing eight “journeys” a week.

For a normal commuter, that would look like return trips between their home and workplace for four days, thus earning them three “free” days on the transport network, assuming they used it weekends.

However, smart users quickly found a way to make the eight journeys in a matter of a couple of hours, and at a very low cost.

These users became known as “Opal runners”, derived from the practice of running back and forth between two stations to tap on and off repeatedly, thus appearing to clock up eight “journeys” quickly.

In practice, “runners” used a variety of means to travel between the stations.

“Currently, some people are running, cycling, driving or even roller-skating between train stations or light rail stops to tap on and off, earning free travel for the week after only paying around $18.00,” the government said.

Opal runners started out as individuals gaming the system.

In an early look at the movement, Fairfax observed about 150 “instances” over several hours where people would tap on at a light rail stop near the newspaper’s offices, only to walk away “from the stop, clearly with no intention of catching a tram.”

But within a month, Opal running became a business.

Reportage found a runner that would max out the trips on a number of cards each Monday morning, and the card owners would pay him “whatever amount they feel is fair”.

“The business is still young,” the runner told Reportage. “I’m basically redirecting the money that would go to Transport for NSW to the customer’s pocket.”

Other running services cropped up that could be entirely booked online.

If it wasn’t the business-like structures cropping up around Opal running then it was the number of people starting to take advantage.

The state government for the first time released figures on the number of journeys notched up by Opal users on key running routes.

On the top “journey” favoured by runners – the 300m distance between Pyrmont Bay and The Star on Sydney’s light rail – the government saw 65,636 “journeys” made on Mondays over a five week period. On the five Fridays in that period, barely 149 journeys were notched up.

It was a similar story for other runner routes around Central Station and between two inner-west train stations.

The loophole isn’t being completely closed – it will still be possible to earn free travel for a week in one day, but runners will now have to waste much more of their Monday to do it, the government said.

“The Opal system currently allows people to walk, run or cycle between stations that are close together, like Macdonaldtown and Erskineville, and accumulate free travel rewards in approximately an hour and a half – without even catching a train or tram. The changes implemented today mean the same process could take at least five hours,” NSW Transport Minister Andrew Constance said.

“The system will be updated to substantially disrupt those people who are improperly earning free travel, by raising the number of transfers needed to make a journey.

“My message is that the changes are in operation as of now – so ‘Opal runners’ don’t have to bother. It’s not worth running out of steam.

“The system changes do not affect other customers because they are not the ones attempting to quickly get charged for more journeys, especially when transferring between light rail stops or train stations while travelling on the same journey.”