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

On German federal motorways, the shortest route to the next emergency telephone is indicated by small black arrows on the roadside delineators (the posts along the road). These arrows point directly toward the emergency phone. This system helps drivers quickly find assistance if needed. Direction markings on guardrails or ground markings on the hard shoulder are not used for this purpose, so focusing on the black arrows on the delineators is key for locating emergency telephones efficiently.