论文标题
大城市道路基础设施的发展
Evolution of road infrastructures in large urban areas
论文作者
论文摘要
美国和世界上的大多数城市都是围绕汽车交通而组织的。特别是，建造了大型建筑物，例如城市高速公路或环道，用于减少汽车交通拥堵。随着公共交通，工作条件，这些结构的未来以及大型城市地区的组织的发展，尚不确定。在这里，我们分析了美国城市的经验数据，并表明它们在不同阈值下显示两个过渡。对于顺序的第一个门槛$ t_c^{fw} \ sim 10^4 $通勤者，我们观察到城市高速公路的出现。第二个阈值较大，并且$ t_c^{rr} \ sim 10^5 $通勤者的顺序较大。为了理解这些经验结果，我们提出了一个基于成本效益分析的简单模型，该模型依赖于基础设施的构建和维护成本之间的平衡以及行程持续时间减少（包括拥塞的影响）。该模型确实预测了这种过渡，并使我们能够根据关键参数明确计算通勤者的阈值，例如时间的平均值，道路的平均能力，典型的建筑成本等。此外，此分析使我们能够讨论这些结构未来进化的可能场景。特别是，我们表明，在许多情况下，由于其巨大的社会成本（包括污染，健康成本等），取消城市高速公路是有益的。在许多城市必须面对翻新这些老化结构或将它们转换为另一种用途的困境时，这种信息特别有用。
Most cities in the US and in the world were organized around car traffic. In particular, large structures such as urban freeways or ring roads were built for reducing car traffic congestion. With the evolution of public transportation, working conditions, the future of these structures and the organization of large urban areas is uncertain. Here, we analyze empirical data for US cities and show that they display two transitions at different thresholds. For the first threshold of order $T_c^{FW}\sim 10^4$ commuters, we observe the emergence of a urban freeway. The second threshold is larger and of the order $T_c^{RR}\sim 10^5$ commuters above which a ring road emerges. In order to understand these empirical results, we propose a simple model based on a cost-benefit analysis which relies on the balance between construction and maintenance costs of infrastructures and the trip duration decrease (including the effect of congestion). This model predicts indeed such transitions and allows us to compute explicitly the commuter's thresholds in terms of critical parameters such as the average value of time, average capacity of roads, typical construction cost, etc. Furthermore, this analysis allows us to discuss possible scenarios for the future evolution of these structures. In particular, we show that in many cases it is beneficial to remove urban freeways due to their large social cost (that includes pollution, health cost, etc). This type of information is particularly useful at a time when many cities must confront with the dilemma of renovating these aging structures or converting them into another use.
