Which innovative retail concept did Singapore's Changi Airport pioneer that revolutionized airport shopping and has since been adopted by major transportation hubs worldwide?

The transportation industry has witnessed remarkable innovations in retail operations at transit hubs. From airports to train stations, these locations have evolved from simple waiting areas to sophisticated retail environments. This poll tests your knowledge about how transportation venues have transformed their retail spaces to enhance passenger experience while maximizing revenue opportunities. Are you familiar with the latest retail trends in transportation hubs?

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The centralized duty-free model where all shopping is confined to a single location after security
The 'street price guarantee' system ensuring airport prices match downtown retail prices
The integrated terminal-mall concept where retail shopping areas blend seamlessly with transit operations
The subscription-based shopping program offering exclusive discounts to frequent flyers