Question 1278 in the bank

What sign warns drivers about an approaching tunnel?

Four signs: blue squares with an arched opening (633, and 634 with a diagonal line), black square with a triangle of cars (127p), red triangle with an arched opening (138).
  1. 633
  2. 127p.
  3. Correct answer: 138
  4. 634

Why this is the answer

The correct answer in the official bank: 138

Warning signs are triangles with a red border, and they alert drivers in advance to what lies ahead. Sign 138 shows a tunnel inside such a triangle, so it warns of an approaching tunnel. The blue square signs 633 and 634 are information signs that mark the tunnel itself and its end. Sign 127p shows a line of vehicles and has nothing to do with tunnels.

Topic: Traffic signs. The bank marks it for these classes: Light truck (C1), Heavy truck (C), Bus (D), Motorcycle (A), Tractor (1), Private car (B).