Possible Clues:

• Pickup line?
• Music to a highway walker's ears
• 'Can I drive you?'
• Question for the stranded
• 'Going somewhere?'
• Motorist's question ... and hint to the ends of 16-, 23-, 46- and 55-Across
• Question to one on the shoulder
• Invitation on the road
• Question for a hitcher
• Question for a hitchhiker