Weather-induced Soil Erosion and Damage to Roads

14 Mr Saktiandi Supaat asked the Minister for Transport (a) how has LTA stepped up on the monitoring of weather-induced problems such as soil erosion which pose a danger to motorists and disrupt traffic; (b) whether there will be an increased frequency of inspection of transport infrastructure to ensure their adequacy to withstand the elements; and (c) what are the long-term plans for pre-emptive measures to safeguard against weather-induced problems on roads and traffic.

15 Mr Melvin Yong Yik Chye asked the Minister for Transport (a) in the past six months, how many potholes have been reported on our public roads; (b) what is the average length of time that LTA takes to repair such potholes; and (c) what is the recourse that motorists can seek when their vehicles are damaged by potholes.

16 Mr Melvin Yong Yik Chye asked the Minister for Transport (a) in the past three months, how many cases of landslips along our public roads have been recorded; (b) whether there are any vehicular damage or injuries that happened as a result of these slope erosion incidents; (c) how many locations in Singapore are prone to such slope erosion incidents; and (d) what are the Ministry’s plans to prevent such incidents from happening.

The Senior Minister of State for Transport (Dr Amy Khor Lean Suan) (for the Minister for Transport): Mr Speaker, Sir, with your permission, may I take Question Nos 14 to 16 together, please?

Mr Speaker: Yes, please.

Dr Amy Khor Lean Suan: Thank you. LTA conducts frequent inspections of over 9,000 lane-kilometres of roads to check for road defects, including potholes. Expressways are inspected weekly, major roads fortnightly, and all other roads once every two months. LTA also receives feedback from members of the public on any road defects and conducts follow-up investigations.

Wet weather conditions exacerbate wear and tear on our road infrastructure. More potholes appear on our roads during periods of heavy sustained rainfall, due to the continuous seepage of water into the road pavements. January 2021 was an exceptionally wet month, with very heavy and prolonged rainfall. From 1 to 31 January 2021, LTA identified 2,570 potholes on our roads, the highest ever number of potholes recorded in a single month, and more than double the number of a typical wet season month.

When a pothole is identified, LTA typically tries to repair it within 24 hours. In January 2021, LTA has tripled its manpower for road repairs. Unfortunately, heavy rain hampers pothole patching works because the road surface needs to be dry in order for the patching materials to bond properly. As of 31 January, about 95% of the potholes have been repaired. Safety critical ones have been prioritised for repairs. LTA is currently working to repair the remaining potholes.

Members have also asked about slope erosions. LTA conducts quarterly inspections of around 200 slopes located near roads, to look out for anomalies. During rainy seasons, LTA increases the inspection frequency for steeper slopes to weekly, as they have a higher risk of soil erosion.

In early January 2021, during downpours, there were two episodes of soil erosion at two different sections of the slope surface along the slip road from TPE(PIE) to Loyang Avenue and Tampines Avenue 7, despite the slope having been lined with a protective covering.

For the first incident on 2 January 2021, LTA repaired the eroded surface and lined about 70 metres of the slope adjacent to the incident site with concrete. The other areas did not show any anomalies, but LTA continued to closely monitor the entire slope as a safety precaution. When the second incident occurred about 100 metres away from the first erosion, LTA was able to detect it immediately and lined it with concrete as well.

In both incidents, the slip road was promptly closed off as a safety precaution and traffic redirected from the area. Other than these two episodes, LTA has not detected other incidents of soil erosion along slopes near roads last year.

When such incidents happen, be it potholes or slope erosions, our priority is rapid response to minimise risks to safety. In addition, LTA also undertakes preventive measures such as resurfacing roads based on condition assessment of the pavement, to enhance their durability. But because these resurfacing works can be disruptive for motorists and costly, we do it in a targeted way. For slopes, if pre-emptive measures are deemed necessary, they will be lined with protective covering to prevent rainwater from seeping into the soil, or reinforced with retaining walls to enhance their stability. LTA will continue to study technology-enabled approaches for monitoring and repair works.

Motorists who have sustained vehicle damages or injuries generally seek recourse from their insurance providers. We encourage motorists to drive safely and watch out for potholes as well as report any defects through the LTA website, the "Snap & Send" function on the MyTransport.SG mobile application, or the Municipal Services Office's OneService application.