At a time when demand is less

• Time of few users
• Like late-night commuter trains
• Non-rush-hour, say
• Not at the time of highest demand
• Reduced-price, most likely
• Not rush hour
• Going to arouse, picked up when it's not so busy
• Outside of rush hour

Wiktionary Word definitions in Wiktionary
a. (alternative form of off-peak English)