Evaluation of multimodal transport for emergency rescue based on online GIS and scheduled timetables

Unlike normalized flow of people and cross-regional transportation of goods, emergency transportation tasks have high requirements for timeliness and accuracy, which in turn places extremely high requirements on organization of transportation resources. Current paper uses modern information technologies such as online information and GIS to coordinate emergency transportation tasks. While considering the simultaneous delivery of portable equipment and materials, aiming at the fastest arrival of emergency rescue personnel in batches, current research studies the integration of batches and multimodal transportation. At the same time, the impact of scheduled timetables of trains and flights on the transportation actions is studied as well. Research shows that, aircrafts may play important roles in emergency transportation under catastrophe scene in China.


Introduction
Affected by factors such as global warming, accelerated population movement and accelerated urbanization, the world has seen a trend of frequent occurrence on the four categories of sporadic event (natural disasters, production safety accidents, public health events and social security events) since the beginning of the 21 st Century. At the same time, various modes of transport have been increasingly developed in Mainland China, including aviation, high-speed railway, highway and even water transport. Different modes of transport have their own advantages and play an extremely important role in the normal economic development. Under the catastrophe scene, emergency rescue and disaster reduction and relief often need cross-regional cooperation since emergency rescue is a kind of high degree of specialization work. And the rescue of some major and serious emergencies usually requires cross-regional mobilization of emergency resources such as personnel, materials and equipment. The relief of Wenchuan Earthquake in 2008 and the support to Wuhan in the fight against COVID-19 in 2020 will be provided.
The core mission of emergency relief is to save people's lives, accompanied by a large amount of relief supplies, emergency rescuers and rescue equipment cross-regional transportation [1] . Multimodal transport may be the best choice for cross-regional emergency transportation, such as joint air-and-road transportation and joint rail-and-road transportation. However, in case of catastrophes (such as giant earthquake, tsunami, volcanic eruption, epidemic prevention and control), the accessibility of different transportation methods, like land, railway and water transportation, are often confronted with difficulties to varying degrees. In recent years, the railway system with fast operation speed and large volume has developed rapidly and played important roles for personnel exchanges in China. Meanwhile, the civil and military aviation, including transport aviation and general aviation, have also played important roles in rescue during previous emergencies, as shown in Figure 1. In addition, during the fight against COVID-19 in the year 2020, airlines in China undertook 80% of the medics to Hubei and 93% of the return transportation, transporting more than 73,300 person-times of medics. According to statistics, Wuhan Tianhe International Airport (WUH) has ensured 2,800 rescue flights takeoff and landing in about 60 days. With the inherent advantages of the flexibility and mobility, CAAC coordinated 141 general aviation enterprises to use 1,001 aircraft for 377 missions, flying 2,360 hours and 7,187 sorties in total [2] .
However, transport process is prolonged due to difficulties in transfer connection during historical emergencies, thus affecting the final emergency rescue effect. Current research on the trans-regional dispatching mode of the whole process of emergency rescue personnel, materials and equipment has significant economic value and social benefit for improving the efficiency of emergency rescue and minimizing the loss of personnel and property.

Methods
Since cross-regional assemble more than tens of thousands of emergency rescue personnel and portable equipment has been more common, based on the emergency rescue resource scheduling requirements, basic information, such as traffic resources around the emergency center. In the process of emergency transport planning, many elements should be fully considered, such as the capacity of different transport modes, the traffic capacity of road networks, the requirements of height limit and weight limit, runway class and guarantee conditions of the airports, etc.
Summarize the planned path of all emergency forces and emergency supplies, and follow the principle of efficiency and economy, and take into account the special urgent attributes of emergency services. When socialized transportation resources do not meet the scheduling needs, the functions of similar transportation resources are integrated to achieve special trains are transported along the route, and special planes converge to set off, and finally form emergency forces and emergency material transportation guarantee plan.

Stage division
Under emergency conditions, comprehensively analyze the circumstances surrounding the emergency center or sites and the airports (including civil aviation airports, general airports and helicopter take-off and landing points), railway stations and bus stations around the geographic location where emergency rescue resources are to be mobilized. At the same time, comprehensively analyze and judge the road capacity, damage, and real-time road conditions under emergency conditions on an emergency management digital map (EGIS) to clarify the distribution of road resources around the incident site. At the same time, combining with current dynamic Internet map data, fully consider the historical traffic situation of railways and roads (for example, historical data during the past 7 days), population heat map and other data to study and judge the current railway and road traffic conditions, and take into account sudden changes. The impact of incidents on road networks, railway lines, airport facilities, etc., supports manual marking of the availability and availability of infrastructure such as road networks, railway lines, and airports, combined with line conditions and meteorological conditions along the way (factors such as typhoons, heavy rains, etc.), promptly remind potential flight delays, train cancellations and other risks for comprehensive evaluation and reference by rescue coordinators [3][4] .
In general, it is proposed to divide the entire emergency transport process into three stages: 1) Stage 1: Assemble at the starting point. Under normal circumstances, whether it is a comprehensive fire rescue force or a national emergency medical rescue team, the members are distributed in different units (fire brigades, medical institutions). After receiving an emergency rescue order, they often need to meet at the location as soon as possible. Point (airport, station) assembly, unified transportation to reach the destination assembly and distribution point.
2) Stage 2: Cross-regional transportation. Generally, in addition to the short distance transport, often have to transfer to remote transport vehicles such as trains, airplanes, the key link in the phase decided to emergency rescue efficiency, also is the key content of this study, both need to match capacity, also must take into account the feasibility of the mode of transportation, such as the requirement of the dangerous goods transport, large excess baggage transport.
3) Stage 3: Destination evacuate. After emergency rescuers and materials arriving around the emergency sites, they need to be quickly transported to the disaster relief location. Normally, there are multiple disaster relief or rescue locations. Correspondence needs to be considered in overall planning and the transit time of Stage 3 is determined accordingly. According to statistics, it takes only about 20 minutes for medical staff to enter Hong Kong from getting off the plane to getting on the bus.
In addition, it is also necessary to consider the waiting time for transfers between stages, as there are great differences among different modes of transportation. Generally speaking, considering the particularity of emergency rescue, emergency rescuers have priority access to traffic facilities. Therefore, the transfer time for roads, railways, and aviation (including the two transfer periods from Stage 1 to Stage 2, Stage 2 to Stage 3) is taken The given value is 15 minutes, 30 minutes and 45 minutes respectively.

Basis of evaluation
Based on the analysis of the scheduling strategy, select no less than 3 optimized scheduling schemes (such as the shortest time, the largest capacity or least intermediate conversion), and visualize them on an emergency management map (EGIS), and support rescue coordinators to conduct dynamic analysis and timely adjustment of transportation routes and routes based on factors such as weather and road conditions.
It should be noted that the core of emergency rescue is to save people lives. After various major emergencies, the first consideration is to save lives and property in the "fire and water". To ensure the efficiency of rescue, personnel, materials and equipment are needed. Specifically, the route is selected based on the objective function of the team that has transported the most in the shortest time. For shortdistance transportation, motorized maneuvering can be considered to reach the front line.

Rendezvous at origin (T 1 )
Based on the online map function of GIS, plan the meeting path from the resident (depending on the type of rescue team, usually local fire brigade, medical and health institutions, etc.) to the local distribution point (train stations or airports). This stage also takes the shortest time evaluate the rendezvous path for the objective function and calculate the rendezvous time.

Cross-regional transportation (T 2 )
Considering the difference of assembling time and transportation mode in different regions, crossregional transportation scheme is selected according to the schedule, train number and flight are determined, and the transport capacity of current train number and flight execution aircraft and other parameters are considered. In response to a public health event, new requirements for the number or type of vehicle to be distributed need to be considered. The time of trans-regional transportation is planned and determined based on the time schedule given by China Rail's official ticketing website (www.12306.cn) [5] and the official web sites of civil aviation management agency [6] .

Destination Evacuation (T 3 )
Focus on how to evacuate emergency rescue personnel to various disaster relief sites quickly after batches of emergency rescue personnel and material are transferred across regions, so that emergency rescue work can be carried out rapidly. During this period of time, it is proposed to use the path and duration obtained from online map planning as a reference, and the shortest time is still used as the criterion to select the optimal path.

Case study
Combining the location of the emergency and the grouping of rescue personnel, based on the available transportation, such as the information of the transportation hubs like the airport and railway stations around the incident, the information of the transportation such as aircrafts, trains, and cars, etc. For county roads and road condition information, as well as relevant air tickets, train tickets and other ticket information, the emergency management department shall take the lead in coordinating reliable information sources and data interfaces with relevant departments.
This article takes the total time from the stations to the place where the incident occurred for important rescue teams in all provinces (municipalities and autonomous regions) as the evaluation index. Due to the randomness of the emergencies, it's really a complex and hard work to determine the task area for every rescue team at the first timing. So, the destination is set to a fixed location, as the epicenter or the center of the disaster city. It should be noted that the emergency rescue forces are currently mobilized across regions in China, usually with provinces as the unit.
Based on the above assumptions and analysis rules, the forces assembled in the past rescue operation of Wenchuan Earthquake on May 12, 2008 and the fighting against COVID-19 in Wuhan during the first half year of 2020 will be analyzed and judged in order to obtain some conclusions. Limited by pages, typical operating point from near and far in all directions are selected in this article.

Case 1 Rescue action of Wenchuan Earthquake, 2008
In the giant 2008 Wenchuan Earthquake (May 12 th , 2008) with a moment magnitude of 7.9 in Sichuan, China, 160,000 emergency rescuers arrived in the disaster-stricken area for earthquake relief from more than 27 provincial administrative regions. The wide area involved, the amount of force mobilized, and the speed of investment all set a historical record for the Chinese and even the whole world disaster resistance.
Since China had not yet established an extensive high-speed rail network that year, civil aviation was the main mode of trans-regional transshipment. However, high-speed rail has extended in all directions in most capital cities in China nowadays. The optimal cross-regional transportation mode and time of 8 typical rescue teams are shown in the following table with Serial number from 1 to 8. Stage and total delivery time can be estimated as shown in Table 1. In Table 1, △ represents transportation by train, ☆means by aircraft and ○ means by highways. It can be seen from the table that aircrafts have great advantages in transportation of 1,000 kilometers or even more than 600 kilometers just like Shaanxi compared with Beijing and Shanghai.

Case 2 Fighting against COVID-19 in Wuhan, 2020
For public health incidents, the rescue coordination process is quite different from other types of incidents. For example, after Wuhan was "closed", aircrafts became almost the only way to get in and out of Wuhan. According to the official report from CAAC, civil aviation transported a total of 302 medical teams, and medical and other rescue personnel (about 38,200, including 3321 sent by the Air Force of PLA) accounted for nearly 90% of the total number of emergency rescue personnel for aiding to fight against epidemic in Hubei during the fight against the epidemic [7][8][9] .
Considering that key hospitals, especially intensive care hospitals, are located in the urban area, the travel time from the airport is often less than one hour. Therefore, the transit time for the third stage is set to 1 hour. Stage and total delivery time can be estimated as shown in Table 2.