Loose road surface ahead
The road surface ahead has loose material such as gravel or stones. Reduce your speed and maintain firm control of the steering. Foreigners should note that loose surfaces can cause skidding more easily than in cooler climates.
Verified as Thai road sign ต.39 from Thai Department of Land Transport sign series on 2026-05-15.
Study guide
Connect this sign to practice
Loose road surface ahead is a hazard cue, not a rule. On the Thai exam that distinction matters. Run a few questions to see how the scenario gets framed: which way to slow, who has priority, and what the next sign is likely to be.
Now see it in questions.
Spotting Loose road surface ahead in isolation is one thing. Recognising it inside a real exam-style question, among lookalikes and trick wording, is another. The diagnostic mixes it in for you.
