Roads and Trade: Evidence from the US
研究美国州际公路对城市贸易量和贸易结构的影响，发现公路显著增加出口重量（弹性约0.5），但对出口总值影响不大，且公路多的城市更专注于生产重型商品。
We estimate the effect of interstate highways on the level and composition of trade for US cities. Highways within cities have a large effect on the weight of city exports with an elasticity of approximately 0.5. We find little effect of highways on the total value of exports. Consistent with this, we find that cities with more highways specialize in sectors producing heavy goods.