Possible Clues:

• Selfish drivers
• 'They may end up as crashing bores, by the sound of them (4,4)'
• Problem drivers
• Maddening motorists
• Sounds as if they might become crashing bores
• They're likely to be honked at
• They may be crashing bores, the sound of them
• They could well be crashing bores, by the sound of them
• They're hard to pass
• Selfish drivers do go rash when given the run-around