The Chicago Area Transportation Study (CATS) set the standard for urban transportation planning during its original 1955-61 genesis years. This study examined CATS' planning methodology during these years and its 1962 regional transportation plan for the Chicago metropolis which had a planning target year of 1980. The subject focus of this study was on expressway planning while the temporal focus was from the late 1950's to circa 1980. The findings of this study revealed four key reasons why CATS' 1962 expressway plan was largely never implemented. These reasons include the inconsistency of some of CATS' 1962 projections for 1980 versus actual 1980 data, the apolitical orientation of CATS, increased urban environmentalism, and rising expressway infrastructure costs. Yet despite the lack of plan implementation, the literature supports the conclusion that CATS did set the standard, at least in its methodology or planning approach. / Department of Urban Planning