Do highway widenings reduce congestion?
利用荷兰高速公路检测环的微观数据，研究发现拓宽工程在短期内（6年）显著减少拥堵，带来可观的出行时间节省，短期福利收益已覆盖40%的投资成本。
Abstract Highway construction occurs nowadays mainly through widening of existing roads rather than building new roads. This article documents that highway widenings considerably reduce congestion in the short run, defined here as 6 years. Using longitudinal microdata from highway detector loops in the Netherlands, we find substantial travel time savings. These savings occur despite strong increases in traffic flow. The welfare benefits in the short run already cover 40% of the widenings’ investment costs. Our article contributes to an explanation why countries invest in roadworks even when the fundamental law of congestion predicts that travel savings disappear in the long run.