Possible Clues:

• Course for retiring soldiers is not the first offering direction to anyone going on a journey perhaps
• Something to read while driving
• Is that an omen finally from Kildare Street? Stop!
• Course for recruit plays a big part in traffic management
• Stop or yield, say
• Aid to motorists
• It's an indication for drivers, by the way
• Exit indicator, e.g.
• MERGE or SIGNAL AHEAD, e.g.
• 'It informs or instructs highway users (4,4)'