If you're transporting explosives and your vehicle breaks down, you should notify other drivers:

Question

If your vehicle breaks down while you are transporting explosives and you need to use warning signals, use reflective triangles or red electric lights. Never use burning signals, such as flares or fuses, when transporting explosives.

Accepted Answer

With reflective triangles.

Answer

With flares.

Answer

By standing on the roadway and waving your arms.