warning sign
Carriageway shifts left ahead
Thai road sign ต.42 — Carriageway shifts left ahead. Meaning: The driving lane shifts to the left ahead, often where the road realigns around an obstacle, bridge, or construction zone. 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: ป้ายเตือนเปลี่ยนช่องเดินรถ
Independent English reference · Source: Department of Highways · Sign ต.42
Road response
On the road
Driver action
What should you do?
Reduce speed and follow the lane markings as the carriageway shifts to the left; do not continue on the old alignment.
Exam-style scenario
Read the situation
Temporary markings carry your lane left while the old alignment continues toward barriers.
Best response: Follow the temporary markings left around the barriers instead of continuing along the old alignment.
Sign comparison
Don’t confuse it
This sign
Carriageway shifts left ahead
Compare with
Carriageway shifts right ahead
Key difference
Both lane edges shift left together rather than ending; the mirrored sign moves the live alignment to the right.
Put sign knowledge into practice.
Answer exam-style questions about road signs, traffic lights, and lane markings in clear English.
