mandatory sign
One-way left
Thai road sign บ.38 — One-way left. Meaning: Traffic on the road ahead must travel to the left in the direction shown by the arrow. Learner-manual coverage: this identity is shown in the current DLT car-driver learner manual. Inclusion does not mean it appears in every theory test.
Thai name: ป้ายเดินรถทางเดียวไปทางซ้าย
Independent English reference · Source: Department of Highways · Sign บ.38
Road response
On the road
Driver action
What should you do?
Traffic on the road ahead must travel to the left in the direction shown by the arrow. Drivers must not enter or continue against that one-way direction.
Exam-style scenario
Read the situation
You reach a one-way entrance where the mandatory arrow directs all traffic to the left.
Best response: Turn left into the one-way street and do not attempt to enter it in the opposite direction.
Sign comparison
Don’t confuse it
This sign
One-way left
Compare with
One-way right
Key difference
The blue arrow sends one-way traffic left across the junction; the mirrored companion arrow sends it right.
Put sign knowledge into practice.
Answer exam-style questions about road signs, traffic lights, and lane markings in clear English.
