What should guide the driver when approaching a railroad crossing:
The position of the barrier and traffic signals.
The requirements of road signs and markings.
Instructions of the person on duty at the crossing.
All the requirements listed.✓الإجابة الصحيحة
الشرح
Approaching a railway crossing requires the driver to reconcile the barrier and light signals with signs, road markings, and any directions from the crossing attendant. Relying on only one source can miss a simultaneous restriction communicated by another.