The second phase of a project to install noise barriers along elevated MRT tracks will be completed in 2022, three years later than the targeted 2019 date.
Transport Minister Khaw Boon Wan told Parliament yesterday that the delay is due to "the need to review the effectiveness" of the project's first phase.
The tender for phase two, which is expected to cover about 9km of tracks, will be called within the next couple of months, he said.
After it is awarded, the Land Transport Authority (LTA) will require time to finalise the designs at locations where the barriers will be constructed, he added. Installation works will start in 2020.
Given the limited hours after train service, he said the project's timeline has to be "closely coordinated" with other ongoing rail maintenance, improvement and upgrading works.
Ms Lee Bee Wah (Nee Soon GRC), had asked when noise barriers at the tracks near Khatib MRT station - a stretch which is part of phase two - would be completed.
She said some of her residents requested the barriers because their sleep has been affected by noise from passing trains.
Explaining the delay, Mr Khaw said: "We were asked to do a post-budget review before because this is a huge project involving hundreds of millions of dollars... The Treasury required us to first break it up into two phases and to do phase two after we have a good review of the results of phase one."
The entire project, which started at end-2013, will cost about $300 million.
Noise barriers can help reduce noise levels from passing trains by about five to 10 decibels, improving the living environment for residents nearby.
The project's first phase was split into two contracts. The first, involving 10km of noise barriers at 16 locations - including Admiralty, Marsiling, Sembawang, Ang Mo Kio, Pioneer and Yew Tee - has been completed.
The second contract, for 3.5km of noise barriers in Clementi, Eunos and Lakeside, is targeted to finish later this year.
Responding to a separate question by Mr Saktiandi Supaat (Bishan-Toa Payoh GRC) on taxi operators adopting surge pricing and how overcharging can be prevented, Second Minister for Transport Ng Chee Meng said taxis will still offer metered rates for commuters booking a cab.
Fares could be higher during peak periods, but also lower during off-peak periods, Mr Ng said.
He added: "We should not prevent the taxi industry from adapting to meet stiffer competition. Livelihoods are at stake, and the competition will drive the industry to deliver better services to commuters."