Final answer:
The correct radio phraseology for accessing the runway while escorting a vehicle is 'Requesting access to the runway while escorting one vehicle.' This format is direct and avoids questions, aligning with aviation communication standards.
Step-by-step explanation:
The appropriate radio phraseology for requesting access to the runway while escorting a vehicle is option 3: Requesting access to the runway while escorting one vehicle. Clear and concise communication is crucial in aviation to maintain safety and efficiency. This statement is direct and provides the necessary information without the use of question form, which is the standard practice in aviation radio communications.