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目前,美国对交通运输重要基础设施进行改善的投资需求日益增长,并已远远超过了实际投资额。据估计,在未来二十年内,为保持公路基础设施达到现有状况与性能,每年必需的花费为516亿美元。这一需求与年计
At present, the U.S. investment demand for improving key transportation infrastructure is growing and has far exceeded the actual amount of investment. It is estimated that in the next two decades, the annual necessary expenditure will be $ 51.6 billion to keep the road infrastructure up to its present condition and performance. This demand and the year