DOH warns motorists as Highway 11 section subsides at Khao Phlueng
Traffic remains open with lane adjustments after damage to the road and shoulder near Khao Phlueng, with full repairs expected within six months.
- A section of Highway 11 near Khao Phlueng has subsided on the downhill side towards Bangkok, caused by erosion from a dislodged drain damaging a retaining wall.
- The Department of Highways (DOH) warns motorists to drive with caution as traffic is adjusted to one lane, with drivers urged to slow down and use the right-hand lane to avoid the damaged area.
- Temporary stabilization measures are in place, with permanent repairs, including a new retaining wall and drainage system overhaul, expected to take up to six months to complete.
The Department of Highways (DOH) has warned motorists using Highway 11 around Khao Phlueng to drive with caution after damage was found on the road and shoulder between km 349+950 and km 349+980 on the Bueng Lak–Nong Nam Sai section.
The affected area is on the inbound, downhill side towards Bangkok.
Traffic remains open, but lanes at the work site have been adjusted for safety.
The DOH clarified on Saturday (June 6, 2026) that the damaged area, near the Khao Phlueng viewpoint on Highway 11, involved a reinforced-soil retaining wall, or MSE wall.
The damage caused the road to subside, forming a void that extended into the traffic lane.
The preliminary cause was a dislodged cross-drain running beneath the road, which led to erosion at the base and damaged the structure.
Uttaradit Highway District 1, therefore, warned people and road users on the Phrae–Uttaradit route, particularly on the downhill section at Khao Phlueng, not to drive close to the left-hand shoulder.
It asked all types of vehicles to use the right-hand lane, especially large trucks, trailers, and private cars, to avoid the damaged area and reduce the risk of further accidents.
Motorists were advised to slow down, maintain a safe distance from vehicles ahead and take extra care during rain or at night.
For urgent measures, the DOH mobilised engineering teams from the Bureau of Bridge Construction, Bridge Construction and Rehabilitation Centre No. 1 (Phichit) and Uttaradit Highway District 1, together with heavy machinery, to the Khao Phlueng area.
The move was aimed at easing the situation and temporarily preventing movement of the road embankment after additional damage was detected on Friday (June 5, 2026).
Initially, the DOH sprayed shotcrete over the slope surface to stabilise the soil layer, saying the stabilised area remains in good and safe condition.
At the same time, backhoe excavators were sent in to fill and level soil at the base of the retaining embankment and adjust the water channel to divert water away from the valley groove.
The measure is intended to temporarily lock the embankment in place and is expected to be completed within one week.
Uttaradit Highway District 1 will check changes in the road surface level every day to closely monitor subsidence.
For on-site safety, traffic on the downhill side has been adjusted to one lane, with signs instructing heavy trucks to keep right to divert large vehicles away from the repair zone and prevent vibration.
Warning signs, warning lights, traffic cones and officials have also been deployed to monitor the area closely.
The DOH is preparing permanent repairs and structural restoration.
It will build a permanent retaining wall with anchors embedded deep into the soil to prevent movement, while overhauling the entire drainage system so water can flow smoothly and will not erode soil beneath the road in the long term.
Cement grout will then be injected to fill voids under the road, before the concrete surface is removed and recast and steel barriers are installed to restore full strength.
The repair and restoration work is expected to take no more than six months.
The DOH asked road users on the route to drive carefully.
Although the road remains open as normal, there will be slight lane diversions around the work site.
People are asked to slow down, observe warning signs and strictly follow traffic signals.
The department apologised for the inconvenience.
Road users can ask for route information or report highway emergencies through the DOH hotline 1586, available 24 hours a day.
