Contactless is standard on the London tube now - you tap a reader on a barrier with your card or phone, and the barrier opens. Same on exit. The system works out the cost as you go, and the maximum cost of multiple journeys is automatically capped.

Chip and pin definitely would definitely be too slow for this. The barriers have to be fast enough to process huge numbers of people at peak times.

Contactless has eliminated all the usual queuing for tickets and/or prepay card topups - except for tourists.