Related Clues:

• Perhaps unrequited love experienced for the first time, yes?
• Revolutionary ace in utterance to grab attention permitting no U-turn
• Like non-return valve
• Not allowing return motion
• Allowing motion in a single direction
• Allowing no return movement
• Traffic sign with an arrow
• Nothing modern ever appears in this kind of street
• You cannot make a comeback along this street
• No traffic is met in such a street
• The only means to ease traffic congestion
• Nothing different -- always moving in a single direction
• Individual means 'not reciprocated'
• Like Madison Avenue
• Kind of street where cars shouldn't meet head-on