Temporary traffic-control sign
Left lane merges into two lanes
Thai road sign ตก.21 — Left lane merges into two lanes. Meaning: A left-side lane merges into two through lanes. 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: ป้ายเตือนเบี่ยงเบนการจราจร
Independent English reference · Source: Department of Highways · Sign ตก.21
Road response
On the road
Driver action
What should you do?
A left-side lane merges into two through lanes. Reduce speed before the signed condition and keep enough space to respond safely.
Exam-style scenario
Read the situation
A left lane ends and joins two continuing lanes beside the work area.
Best response: Leave the ending left lane by merging into a safe gap in one of the two continuing lanes.
Sign comparison
Don’t confuse it
This sign
Left lane merges into two lanes
Compare with
Right lane merges into two lanes
Key difference
The entering or ending lane is on the left of the two through lanes; the mirrored diagram places it on the right.
Put sign knowledge into practice.
Answer exam-style questions about road signs, traffic lights, and lane markings in clear English.
