What does this traffic sign combination indicate?

The traffic sign combination you see indicates caution regarding horse-drawn vehicles. The triangular sign alerts drivers to potential dangers associated with the presence of horses and carriages on the road. The supplementary rectangular sign specifies that horse-drawn vehicles are in use in that area.

1. The first part emphasizes that drivers should be aware of these vehicles, as they can be slower and require more space.
2. The second part highlights that horse-drawn vehicles have legal rights to be on the road, but it does not explicitly state that they have priority over motor vehicles.

In essence, it's crucial for drivers to understand both the risks and the presence of horse-drawn vehicles to ensure safety for all road users.