Despite massive investments in transportation infrastructure, traffic congestion remains a major societal and public policy problem. Intelligent Transportation Systems (ITS) have been proposed as a potential solution to this challenge, but their effectiveness has remained unclear in both research and practice. To understand whether and how ITS affect traffic congestion, we consolidate a unique longitudinal dataset on road traffic and the deployment of a large federally-supported ITS program in the United States (U.S.)—511 Systems—in 99 urban areas between 1994 and 2014. The difference-in-differences estimates show that the adoption of 511 Systems is associated with a significant decrease in traffic congestion, saving over $4.7 billion dollars and 175 million hours in travel time annually in U.S. cities. 511 Systems also reduce about 53 million gallons of fossil fuel consumption and over 10 billion pounds of CO2 emissions. We offer two theoretical explanations for this effect: (i) ITS help individual commuters to make better travel decisions; and (ii) ITS help local governments to develop an urban traffic management capability. Empirical evidence supports the underlying theoretical mechanisms and shows that ITS help commuters to schedule travel more efficiently, choose better navigation routes, and optimize their work-trip transportation mode. Second, the effect of ITS is contingent upon road supply and public transit services. We also find that the traffic-reducing effect of ITS is larger when commuters use more online services for traffic information and when state governments incorporate more functionalities into their 511 Systems. This study contributes to the literature on IT capabilities, public-sector IT value, and the societal impact of IT, while also extending the transportation economics to IT-enabled traffic interventions. Finally, we inform policymakers of ITS as a cost-effective means to mitigating traffic congestion.

中文翻译：

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缓解交通拥堵：智能交通系统的作用

尽管在交通基础设施上进行了大量投资，交通拥堵仍然是主要的社会和公共政策问题。已经提出了智能运输系统（ITS）作为应对这一挑战的潜在解决方案，但是其有效性在研究和实践中仍不清楚。为了了解ITS是否以及如何影响交通拥堵，我们在1994年至2014年期间，在99个城市地区的道路交通以及由美国联邦政府支持的大型ITS程序511 Systems的部署中，整合了一个独特的纵向数据集。差异估计表明，采用511系统与交通拥堵显着减少有关，在美国城市中，每年可节省47亿美元以上的时间和1.75亿小时的旅行时间。511系统还减少了约5300万加仑的化石燃料消耗和超过100亿磅的二氧化碳排放量。为此，我们提供两种理论解释：（i）ITS帮助个人通勤者做出更好的出行决策；（ii）ITS帮助地方政府发展城市交通管理能力。经验证据支持基本的理论机制，并表明ITS帮助通勤者更有效地安排行程，选择更好的导航路线并优化他们的出行运输方式。其次，智能交通系统的影响取决于道路供应和公共交通服务。我们还发现，当通勤者使用更多的在线服务来获取交通信息时，以及州政府将更多功能纳入其511系统中时，ITS的交通减少效果会更大。这项研究为有关IT能力，公共部门IT价值和IT的社会影响的文献做出了贡献，同时还将运输经济学扩展到支持IT的交通干预措施。最后，我们告知政策制定者ITS是减轻交通拥堵的一种经济有效的手段。