What is it about?
When a traffic crash happens, we often think about the immediate harm—fatalities, injuries, and damaged vehicles. But there is another hidden cost most people overlook: traffic delays. This study uses taxis as "mobile traffic sensors" to measure how crashes slow down the upstream traffic. The disruption to traffic caused by traffic crashes is estimated based on the real-time speed captured by taxi GPS near the crash location. The affected travel speed is then compared to the historical traffic speed to identify the delays. In addition, the total traffic volume is considered to estimate the total time lost by drivers and passengers affected by the crash-induced congestion. The study found that in 2021 alone, traffic crashes caused over 700,000 hours of delays in Hong Kong, costing the city US$11 million in lost time.
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Why is it important?
This study is important in multiple ways. First, it offers unique insights about traffic crash costs as most studies focus on the direct costs of traffic crashes (like medical bills or vehicle repairs). This research highlights the indirect cost—time lost in traffic—which affects thousands of commuters, businesses, and emergency services daily. Secondly, the study is timely as cities worldwide are struggling to address traffic congestion and road safety issues. This study offers a low-cost method (using existing taxi GPS data) to measure delays, making it accessible for cities without expensive traffic sensors. Thirdly, this study has practical implications. It can facilitate the planning of emergency responses. Knowing the locations, time and conditions that traffic crashes caused the worst delays, governments can allocate extra resources to improve road safety and to handle traffic crashes more effectively (like deploying tow trucks or police) when they happened. Fourthly, it helps to raise public awareness. Quantifying the US$11 million loss underscores why preventing crashes is not just about safety—it is also about saving time and money for everyone. Finally, this study has broader applications. The newly-developed methodology can be applied worldwide. Any city with taxi or ride-hailing data can replicate this approach to uncover hidden congestion costs and improve traffic management.
Perspectives
My research team has always believed that understanding the true costs of transportation beyond “out-of-pocket” costs is important to achieving sustainable transportation. Traffic crashes represent a major negative transport externalities not only through inflicting traffic fatalities and causalities but also causing and/or aggravating traffic congestion, which, in turn, lowers fuel efficiency, worsens air pollution and increases traffic noise. It is hoped that this research paper can inspire more in-depth research on measuring and analysing the true costs of traffic crashes, especially using multi-sourced and real-time data collected by various smart devices in cities.
Becky Loo
University of Hong Kong
Read the Original
This page is a summary of: Cost of travel delays caused by traffic crashes, Communications in Transportation Research, December 2024, Tsinghua University Press,
DOI: 10.1016/j.commtr.2024.100124.
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