What does a reflectorised triangle placed on the side of the road mean?

What does a reflectorised triangle placed on the side of the road mean?undefined
There's a breakdown or crash ahead
There are roadworks ahead
There's a special event ahead
There's a one-way bridge ahead and you don't have the right of way

The red reflective triangular sign indicates that a vehicle is broken down or an accident has occurred ahead. Please reduce your speed.