mandatory sign
Minimum speed (30 km/h)
Thai road sign บ.54-30 — Minimum speed (30 km/h). Meaning: Drivers must not travel below 30 km/h where this minimum-speed control applies, unless traffic or safety conditions require otherwise. 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: ป้ายจำกัดความเร็วขั้นต่ำ
Independent English reference · Source: Department of Highways · Sign บ.54-30
Road response
On the road
Driver action
What should you do?
Drivers must not travel below 30 km/h where this minimum-speed control applies, unless traffic or safety conditions require otherwise.
Exam-style scenario
Read the situation
On a clear road controlled by this sign, you travel at 20 km/h without a traffic or safety reason.
Best response: Increase to at least 30 km/h when safe because no traffic or safety condition justifies 20 km/h.
Sign comparison
Don’t confuse it
This sign
Minimum speed (30 km/h)
Compare with
Speed limit (30 km/h)
Key difference
The blue disc requires at least 30 km/h when safe; the red-ring 30 prohibits speeds above that number.
Put sign knowledge into practice.
Answer exam-style questions about road signs, traffic lights, and lane markings in clear English.
