How can you tell the shortest way to the next emergency telephone on federal motorways?

You need to identify multiple indicators for finding the shortest way to the next emergency telephone on federal motorways. The correct combination includes:

1. Black arrows on the delineators, which provide directional guidance.
2. Direction markings on the guardrails, which assist in determining the location of the next emergency phone.
3. Ground markings on the hard shoulder that also indicate proximity to emergency telephones.

Each of these indicators plays a crucial role in ensuring drivers can quickly locate help in case of an emergency. Understanding all relevant options helps promote safety and efficient response measures on the roads.