A physics based one-dimensional transient seven partial differential equation model is proposed to study the oxygen storage dynamics and cold start behavior of a three-way catalytic converter. The model uses the recently published simplified kinetic model, is computationally efficient and may be used for offline TWC outer loop controller design and validation. The proposed TWC model is validated using emissions data collected in a vehicle over multiple drive cycles including FTP cycles. The internal mass transfer approximation is confirmed by comparing with a detailed washcoat diffusion-reaction model and is observed to be consistent for all practical purposes. The results are also used to study the qualitative and quantitative errors in emission and oxygen storage predictions caused by axially averaging thus identifying the region of applicability of the simpler axially averaged seven ordinary differential equation model. (c) 2014 Elsevier Ltd. All rights reserved.