Define a single primary metric for "Uber ride success"

Design one primary, comparable metric for ride success across markets and cohorts. Provide:

1. The exact formula and units.
2. Inclusion/exclusion rules for canceled, no‑show, reassigned, shared (pooled), and multi‑leg trips.
3. The aggregation window (trip vs daily vs rolling 28‑day) and handling of right‑censored or incomplete trips.
4. Normalization so cities with different trip lengths, surge, and traffic are comparable.
5. Guardrails to prevent gaming (e.g., incentives to cancel to avoid late arrivals).
6. A validation plan showing the metric’s sensitivity and directionality using historical backtests and an A/B test design (primary/secondary metrics, MDE, sample size, and power).

Finally, list two plausible failure modes (e.g., Simpson’s paradox across neighborhoods, seasonality drift) and how you’d detect and mitigate them.