<p>Achieving global climate commitments requires credible climate action grounded in rigorous measurement, reporting, and verification (MRV). However, most carbon registries rely on loosely organized MRV processes that are frequently criticized for inadequate verification, double counting, and limited transparency. This paper introduces a stakeholder-oriented architecture of a blockchain-based carbon registry platform for Climate Action in Transportation (CATchain-R) that (i) integrates standards-aligned MRV to record goals, plans, actions, and tokenized carbon credits in a tamper-evident audit trail, and (ii) constructs a carbon credibility index to assess climate action’s delivery against stated goals. To demonstrate this approach, we apply a System Dynamics model using New York City (NYC) transportation emissions (2005–2050) under two scenarios: business as usual and a U.S.-aligned reduction trajectory. Under business as usual, emissions decline too slowly to meet NYC’s 2050 emissions goal, widening the gap between the annual emissions goal and emissions delivery and increasing the potential need for external credits. Under the U.S.-aligned trajectory, the gap closes and credibility improves steadily toward 2050. These results show how pairing standards-aligned MRV with explicit credibility measurement can improve transparency and provide policy-relevant levers for credible climate action in transportation.</p>