Possible Clues:

• Permitting movement in one direction only
• Revolutionary ace in utterance to grab attention permitting no U-turn
• Like non-return valve
• Describing a street where vehicles shouldn't meet head-on
• Type of travel ticket
• The only means to ease traffic congestion
• You cannot make a comeback along this street
• Not allowing return motion
• There's never anything fresh in the system
• Ticket request