While travel on the Downtown Line (DTL) will be free for six days after its second stage opens in a week's time, commuters will have to start and end their journeys on the line to benefit.

From next Sunday to Jan 1, rides will be free along the 12 stations of the DTL2 and the six Downtown Line 1 stations, which opened two years earlier.

However, the Land Transport Authority (LTA) is reminding commuters to start and end their journeys at DTL stations to travel for free during that period.

"Commuters who are travelling through DTL as part of their journey from/to other rail lines will pay normal fares," the LTA said.

This rule also applies to commuters transferring to the DTL2 from the Bukit Panjang LRT line at Bukit Panjang station, or from the North-South Line at Newton station. At these two interchange stations, commuters have to tap out of the fare gates and enter a public area before tapping in again to the DTL2.

These are considered transfers on a single trip, and not the start of a new journey at a DTL station. Normal fares will thus apply.

However, if commuters take a bus to a DTL station, hop onto the line and exit at another DTL station, they will get to travel for free.

Bukit Panjang resident Ameer Hussain, 26, reckons the authorities should extend free travel to commuters transferring from the LRT. "At least (that way) everyone residing in Bukit Panjang can enjoy the free travel for that period," he said.

Still, like fellow residents in the area, the claims executive is looking forward to the DTL2.

The line will offer him a faster ride to the city, and he expects to shave off 30 minutes from his daily commute by taking the MRT to his office in Telok Ayer instead of the bus.

Holland-Bukit Timah GRC MP and Zhenghua grassroots adviser Liang Eng Hwa said costs were likely a consideration when deciding how widely the free travel scheme could be applied across the MRT network.

Mr Liang said the six days of free travel are like an extension of the unlimited free rides given during the open house on Dec 6, which aimed to get people to familiarise themselves with the stations.

When the DTL1 was launched in December 2013, commuters also enjoyed free rides on the line for the first 11 days.

About 300,000 trips were made and the free-travel initiative cost around $260,000, the LTA said.

The 16.6km DTL2 extends the MRT network to the north-western region of Singapore, such

as Bukit Panjang, and passes through the Bukit Timah corridor. It will connect to the DTL1 at Bugis station.