Possible Clues:

• Traveller in a vehicle, not the driver
• 15 across may have one
• Traveller’s means of contact crossing headland going north
• Hand green form to traveller
• One is apt to be driven
• Rider
• No driver may proceed on change to green
• Weak team member transferred by coach, perhaps
• So carried as to get by, to the making of the end of 1 across
• One driven to overtake green convertible