This paper examines the impact of the Interstate Highway System, constructed between 1950 and 1990 in the United States (US), on racial segregation. To provide causal estimates, I use the 1947 plan of the Interstate Highway System, a variant of the 1947 plan that connects city center pairs in this plan through shortest-distance and exploration routes in the 16th-19th century, as the instruments for actual highways built. Empirical results from census tracts in the US show that the construction of highways led to sorting along racial lines. I find strong evidence of heterogeneous effects based on the initial black population. I do not find any impact of highways on neighborhoods which have a lower share of initial black population. However, there is an increase in the share of the black population for neighborhoods located in close proximity to highways, and which have a higher share of the initial black population. This increase is driven by the white population moving out and black population moving into these neighborhoods. I demonstrate that whites that moved out of neighborhoods, now commute to work, made possible due to access provided by highways. These residents were on average better educated and had a higher income than the residents moving into the neighborhoods. The reasons for this movement are disamenities emanating from highways, and racial preferences for social interactions. Finally, I show that this relationship between highways and segregation is also observed at the aggregate level. Empirical estimates indicate that one new highway passing through the central city leads to 0.02 units increase in the dissimilarity index for the metropolitan area.

中文翻译：

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高速公路和隔离

本文探讨了美国 (US) 1950 年至 1990 年间修建的州际公路系统对种族隔离的影响。为了提供因果估计，我使用 1947 年州际公路系统规划，该规划是 1947 年规划的一个变体，通过 16 至 19 世纪的最短距离和探索路线连接该规划中的市中心对，作为实际高速公路的工具建造的。美国人口普查区的实证结果表明，高速公路的建设导致了种族分类。我发现了基于最初黑人人口的异质效应的有力证据。我没有发现高速公路对黑人人口比例较低的社区有任何影响。然而，靠近高速公路的社区的黑人人口比例有所增加，并且这些社区的初始黑人人口比例较高。这一增长是由白人人口迁出和黑人人口迁入这些社区推动的。我证明，由于高速公路提供的通道，搬出社区的白人现在可以通勤上班。这些居民平均受教育程度更高，收入也高于搬入社区的居民。这场运动的原因是高速公路带来的不便以及社交互动的种族偏好。最后，我表明高速公路与种族隔离之间的这种关系也可以在总体层面上观察到。实证测算表明，新建一条高速公路穿过中心城区会导致都市区的相异指数增加0.02个单位。