This dissertation examines how people understood the phenomenon of traffic congestion in Boston in the 1890's and 1920's, tracking the evolution of their ideas between two periods. Then, as today, public discussions of policies to relieve congestion were based upon ideas about such issues as what causes congestion and why it matters. To understand how congestion was perceived in these eras, I used a case study approach, looking at discussions of it during two sets of planning debates. The first case is a debate from 1891 to 1894 that led to the building of a subway in downtown Boston. The second case is a debate in the mid-1920's over plans for the so-called "loop highway," a boulevard running through the downtown. I posed three research questions to limit and define the meaning of the term "perceptions" for this analysis: why did Bostonians think traffic congestion was a problem, what did they think caused congestion, and what policies did they think might reduce it? To answer these questions, I analyzed the words of the people involved in the debates, using materials such as newspapers, government publications, and magazines. Three themes stand out among the conclusions I drew about perceptions of congestion during the two periods. First, the factors people perceived as causing congestion were closely linked to the policies they favored. Second, most people didn't actually talk much about how they perceived congestion, even though they believed it was a problem. This relative silence reflects the fact that ideas about congestion were not particularly controversial. Third, many perceptions that Bostonians held about congestion were not only accepted as conventional wisdom within each time period, but they changed very little across the two periods - people understood congestion in the 1890's in many of the same ways that they did in the 1920's, even though traffic conditions had changed radically in the intervening years. For example, the favored policies were major capital projects; while regulatory approaches were proposed, opposition from interest groups or the public blocked the implementation of all but the most limited new rules.
