Research on Route Optimization of Hazardous Materials Transportation Considering Risk Equity

sustainability Article Research on Route Optimization of Hazardous Materials Transportation Considering Risk Equity Liping Liu , Jiaming Li , Lei Zhou, Tijun Fan * and Shuxia Li Business School, East China University of Science and Technology, Shanghai 200237, China; [email protected] (L.L.); [email protected] (J.L.); [email protected] (L.Z.); [email protected] (S.L.) * Correspondence: [email protected] Abstract: The consequences of a hazmat accident can be catastrophic due to the characteristics of hazardous materials. Different from the models, which are constructed from the perspective of “government-carrier”, this paper considers the three objectives of the risk, the cost, and the compensation cost from the “government-carrier-public” perspective, so as to construct a route optimization model of hazmat transportation considering risk equity. Moreover, considering that the difference in regional emergency response time will significantly affect the risk, this research incorporates the emergency response time into the transportation risk assessment function, and realizes risk equity by minimizing the total compensation cost based on the difference in regional emergency response time. To solve the proposed model, a multi-objective genetic algorithm based on linear weighting is designed. The results obtained from the case study verify the necessity of considering the risk equity in the route optimization model of hazardous materials transportation and prove that the established model and algorithm can find an optimal route that meets the expectations of the government, the carrier, and the public. Keywords: hazardous materials; route optimization; risk equity; multi-objective genetic algorithm; Citation: Liu, L.; Li, J.; Zhou, L.; Fan, emergency response time T.; Li, S. Research on Route Optimization of Hazardous Materials Transportation Considering Risk Equity. Sustainability 2021, 13, 9427. 1. Introduction https://doi.org/10.3390/su13169427 Hazardous material (hazmat) refers to any type of substance that is capable of causing Academic Editor: Armando Cartenì harm to people, property, or the environment. The transportation of hazmat is essential not only for industrial countries like Germany and Canada, but also for developing countries, Received: 7 July 2021 resulting in the fact that the amount of hazmat transportation has reached an unprecedented Accepted: 17 August 2021 level in the past decade. Because many hazardous materials are flammable, explosive, or Published: 22 August 2021 corrosive, the risk generated by an accident during transportation must be considered; otherwise, the consequences will be catastrophic. For example, in July 2013, a driverless Publisher’s Note: MDPI stays neutral train with 72 tank cars of petroleum crude oil derailed in the city center in Lac-Mégantic, with regard to jurisdictional claims in Quebec, Canada, causing the death of at least 42 persons. On 1 July 2019, a tanker truck in published maps and institutional affil- Nigeria overturned and caught fire, leading to 48 deaths, and the number of injuries was iations. greater than 90. On 13 June 2020, a truck transporting liquefied petroleum gas exploded on the Shenhai Expressway in Wenling City, Zhejiang Province, killing 20 people and seriously injuring 24 others. Considering the tremendous consequences of a hazmat accident, many governments have established specific regulations for hazmat transportation. In addition, Copyright: © 2021 by the authors. many studies on hazmat transport have been conducted in terms of risk assessment, routing, Licensee MDPI, Basel, Switzerland. network design, etc. Some literature [1–3] on route optimization of hazmat transportation This article is an open access article usually establish a model considering the transportation risk and transportation cost from distributed under the terms and the perspectives of “government-carrier”. conditions of the Creative Commons However, with the development of society, the public is given increasing importance Attribution (CC BY) license (https:// to equity, and the concept of equity has been introduced into various research fields. For creativecommons.org/licenses/by/ the transportation of hazmat, apart from the total network risk, the risk equity, i.e., the 4.0/). Sustainability 2021, 13, 9427. https://doi.org/10.3390/su13169427 https://www.mdpi.com/journal/sustainability Sustainability 2021, 13, 9427 2 of 18 “fairness” of the spatial distribution of risk, should also be considered. When a certain route is selected as the transportation route for hazmat, it will naturally increase the risks around the route. Therefore, some literature [4,5] has begun to add the objective of risk equity to establish a route optimization model of hazmat transportation considering transportation risk, transportation cost, and risk equity from the “government-carrier-public” perspective. When assessing transportation risk in the route optimization model of hazmat transportation, studies [6–9] have adopted the population exposure risk approach. However, they mostly select the optimal route from the perspective of ex-ante planning, ignoring the importance of ex-post processing. When a hazmat accident occurs during transportation, the response of emergency departments near the link will decrease the harm. Therefore, it is of great practical significance to consider the impact of the emergency response time on the transportation risk and risk equity. By integrating the emergency response time, we present a more practical risk assessment approach in order to construct a route optimization model of hazmat transportation from the perspective of ex-post processing. The main contributions of this study are that the emergency response time of the emergency departments around the link is included in the transportation risk assessment function. In the risk equity model, the risk compensation is made for the links that exceed the average risk of the selected route from the perspective of the risk compensation cost to highlight the risk equity. The study is structured as follows. The related literature is summarized in Section2 . Model building is presented in Section3. Section4 introduces the Solution produce. The computational results of the numerical study are presented and analyzed in Section5, before ending with the conclusions and future research. 2. Literature Review In this section, we briefly review several streams in hazmat transportation research relevant to this paper: (1) Risk assessment, (2) route optimization, and (3) risk equity consideration. 2.1. Risk Assessment The risk caused by an accident during hazmat transportation makes the transportation problem of hazmat much more complicated than when other materials are moved. How to measure the transportation risk of hazmat is one of the important issues in the field of hazmat transportation, because how to reduce the accidents of hazardous materials has become an important and urgent research topic in the safety management of hazardous materials [10]. The risk makes the transportation problem of hazmat much more complicated than when other materials are moved. Therefore, a variety of models have already been proposed to assess the risk in hazmat transportation. Alp [11] used the approach of Traditional Risk to capture risk. Saccomanno and Chan [12] proposed the Incident Probability model, which focused on using accident probability to represent risk. The Population Exposure model was used to measure the risk in hazmat transportation [13–17]. Erkut and Ingolfsson [18] proposed three risk measurement models based on the avoidance of major disasters. Many popular risk assessment approaches in earlier studies are summarized [19]. 2.2. Route Optimization It is necessary not only to evaluate the transportation risk of hazmat to construct a transportation risk assessment function, but also to consider the influence of road speed limits, traffic restrictions, vehicle capacity, road capacity, and other factors on the route optimization model of hazmat transportation during the transportation, so as to construct a route optimization model that can better comprehend the transportation situation of hazmat in reality. At present, many studies focus on the measurement of population risk in the route optimization of hazmat transportation. Considering factors such as the number of ex- posed people and accident probability in the transportation of hazmat, scholars have Sustainability 2021, 13, 9427 3 of 18 constructed the route optimization models of hazmat transportation that consider population risks [20,21]. Afterwards, Qu et al. [22] made improvements to the traditional model in terms of transportation methods, accident probability, and consequences. Bronf- man et al. [23] maximized the distance from population centers to hazmat transportation routes to reduce risk. Financial risk assessment tools such as VaR and CVaR have also been introduced in the route optimization model of hazmat transportation that consider population risk [24,25]. In addition to considering minimizing the total population risk, scholars also pay more attention to the trade-off between the two goals of risk and cost from the perspective of the government and the enterprise [1–4]. Scholars have begun to pay attention to the influence of uncertain factors such as road closures and emergencies on the route optimization of hazmat transportation considering population risks. Fan et al. [26] constructed a route optimization model considering road closure to solve the

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