Transportation systems serve important roles during emergencies, in particular for evacuations. However, efficient travel during these life-and-death scenarios can be adversely impacted by external conditions, such as unnecessary and unneeded travel. This research sought to enhance the understanding of the effects of these conditions by analyzing shadow evacuations, and their impact on regional traffic operations in megaregions, more broadly. The research was based on simulations of a range of hurricane evacuation threat scenarios in the Gulf of Mexico building upon prior study using TRANSIMS. These assessments are also targeted at what many assume could be worst case evacuation conditions and pushing the limits of current simulation modeling capability. Among the broader findings of this work was that shadow evacuation participation rates did not significantly impact the evacuation clearance times within mandatory evacuation areas of the megaregion as long as demand could be temporarily spread out. This finding does not, however, suggest that the shadow evacuations have no impact on evacuation processes. High rates of shadow evacuees can cause significant congestion if they are not able to exit critical routes before mandatory evacuees reach areas further away from the coast.

运输系统在紧急情况下，尤其是在疏散中，起着重要的作用。但是，在这些生死攸关的情况下，高效旅行会受到外部条件（例如不必要和不必要的旅行）的不利影响。这项研究试图通过更广泛地分析阴影疏散及其对巨型区域的区域交通运营的影响，来增强对这些条件影响的理解。该研究基于对墨西哥湾一系列飓风疏散威胁情景的模拟，该模拟基于先前使用TRANSIMS进行的研究。这些评估还针对许多人认为最坏情况的疏散条件，并推高了当前模拟建模能力的极限。在这项工作的更广泛发现中，只要需求可以暂时分散，影子疏散参与率不会对大区域强制疏散区域内的疏散清理时间产生重大影响。但是，这一发现并不表明阴影疏散对撤离过程没有影响。如果高比例的阴影避难者无法在强制性避难者到达远离海岸的区域之前离开关键路线，则可能导致严重的拥堵。