This pilot study challenged two pieces of conventional wisdom related to transit-oriented development: (a) the popular but unproven principle of a 0.5-mi radius threshold and (b) its concentric circular shape. On the basis of a detailed literature review, the current research traced the origins of the ideas of a 0.5-mi radius and a 0.25-mi radius and explored the concept of acceptable access distance as an alternative to the current rule-of-thumb threshold distance. An acceptable walking distance was hypothesized to be positively influenced by microlevel walkability. A case study was undertaken to test the impact of micro level walkability on the acceptable walking distance to a station. On the basis of a station user survey and walkability audit administered in the station area of Mountain View, California, a regression analysis was performed to estimate a transit user acceptable access walking distance. A second analysis was conducted to test the existence of a critical walk ability zone in which microlevel walkability was more influential within the zone than outside it. Two access mode choice logit models were built with different sets of travelers selected on the basis of their home origins, and the explanatory powers of the two models were compared. On the basis of these two analyses, the major findings were the following: the acceptable walking distance to a station could be extended through improvements in the microlevel walkability along the major pedestrian corridors that led to the station and a donut-shaped critical walkability zone might exist.