City-scale transit is the harshest proving ground for access tech: peak crowds, near-zero tolerance, 24/7 operation. Its evolution path is clear.
Phase 1: QR scanning
From paper tickets to dynamic QR, riders scan to pass. Low cost and easy to roll out, but peaks need phone-in-hand and stall, with a clear experience ceiling.
Phase 2: face frictionless passage
After enrollment, riders "pass as they approach", sharply improving throughput and cutting queues. The keys are on-device 1:N speed and accuracy, plus liveness to block impersonation.
Phase 3: multimodal fusion
Face, QR, card and NFC coexist on one terminal, auto-switching by person: locals by face, visitors by QR, special groups by card — full population coverage.
Engineering essentials
High concurrency stresses on-device compute and stable passage; data security demands private deployment and tiered permissions; O&M demands bulk permission push and real-time alarm streaming. None can be missing.
Verifiable benchmark
From CoolCode deployments: face terminals run at metro turnstiles across 25 cities, with on-device 1:N matching under 300ms — a baseline for "high concurrency + in-house algorithm" capability.