mandatory sign
Keep left
Thai road sign บ.40 — Keep left. Meaning: Drivers must pass to the left of the sign or obstruction. 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: ป้ายให้ชิดซ้าย
Independent English reference · Source: Department of Highways · Sign บ.40
Road response
On the road
Driver action
What should you do?
Drivers must pass to the left of the sign or obstruction.
Exam-style scenario
Read the situation
A refuge island divides your lane and this sign is mounted on its nose.
Best response: Steer to the left of the refuge island and keep clear of its nose.
Sign comparison
Don’t confuse it
This sign
Keep left
Compare with
Keep right
Key difference
The arrow slopes down-left and requires passing on the obstruction's left; the mirrored sign requires the right side.
Put sign knowledge into practice.
Answer exam-style questions about road signs, traffic lights, and lane markings in clear English.
