Statistical analysis of typical elevator accidents in China from 2002 to 2019

The data of typical elevator accidents in China used here were obtained from the Special Equipment Safety Supervision Bureau of State Administration of Market Regulation. Interested readers can find the detailed introduction of the State Administration of Market Regulation (SAMR) of China in [7]. The Special Equipment Safety Supervision Bureau is a subordinate department of the SAMR, which is responsible for supervising the safety of special equipment (such as drawing up the catalogue of special equipment and safety technical specifications, supervising and inspecting the implementation of relevant legal standards for special equipment, supervising and administering special equipment inspection institutions and inspection personnel, organising the investigation and handling of special equipment accidents and conducting statistical analysis, etc.). It is the most common and official source of statistical data for special equipment accidents in China.

However, during data collection and collation, some information on the historical data was missing in the database. To facilitate the statistical analysis of the related data, we filled in the missing information based on the description of the accident process and other existing information, and deleted the cases in which the missing information cannot be analysed based on the existing information, and also deleted the factors containing a large amount of missing information including the industry and the age of the casualties. Eventually, this study collected the data of 412 typical elevator accidents in China for the period 2002 to 2019, each of which has more than one casualty. Thus, the sample’s information of these 412 accidents used for the analysis is as follows:

Date

The parameters and their possible states of the accident samples are shown in Table 1.

This study made a statistical analysis on the data of typical elevator accidents in China for the period 2002 to 2019. After sorting out the data provided by the Special Equipment Safety Supervision Bureau of SAMR, the basic information of the accidents was preprocessed, and the relevant factors shown in Table 1 are obtained. Analyses were made according to the number of accidents, deaths and injuries. Moreover, we adopted the method of descriptive statistics to study the differences between different types of elevators in the typical elevator accident data using occurrence stage, casualty’s identity, accident type and accident causes. The results of the descriptive statistical analysis were shown in Section 3. In Section 4, the statistical results were discussed in detail, and some countermeasures and suggestions to prevent similar accidents were proposed. Conclusions were drawn in Section 5.

According to the classification of elevators in the ‘Catalogue of Special equipment’ [1], the 412 elevator accident cases could be classified into three categories namely lifts, dumbwaiters and escalators (passenger conveyors included). Lift is a compartment mounted on a shaft to raise and lower people or goods to different floors or levels. A dumbwaiter is utilised to carry things from one floor of a building to another. It can only be utilised for carrying goods. Escalator is a moving staircase, which consists of a cycle belt of steps driven by a motor and utilised to transport people between the floors of a public building. The passenger conveyor, which transports people at a horizontal or tilt angle of less than 12° has a similar structure like the escalator, was categorised as an escalator here.

Figure 2 shows categorisation of the 412 elevator accidents:347 occurred in the lift, accounting for 84.22%; 44 accidents occurred in escalator or passenger conveyor, accounting for 10.68%; and 21 accidents occurred in dumbwaiter, accounting for 5.10%. This is similar to the proportion of various types of elevators used by China over the years [3]. According to [9], due to the limited operating areas, the escalators (passenger conveyor included) are mainly used in shopping malls, subway stations and other large-scale public places with large passenger flow. Furthermore, compared with lift, escalators adopt an open working mode, which can reduce the probability of accidents in terms of running speed and equipment characteristics. As for the dumbwaiter, because it is only utilised to transport goods, the frequency of accidents with casualties is even lower. Therefore, the frequency of accidents of above three types of elevators such as high to low lifts, escalators (passenger conveyors included) and dumbwaiters is shown here.

Fig. 2

The 412 elevator accidents analysed here caused a total of 527 casualties, of which 331 died, accounting for 62.81% of the total casualties while 196 were injured accounting for 37.19%. The details are shown in Figure 3. Overall, dumbwaiter has the most serious consequences, with a high death ratio (Deaths/Deaths+Injuries) of 0.95, followed by lift with a death ratio of 0.66 and escalators (passenger conveyors included) with a death ratio of 0.22. Based on the above statistical analysis, although the frequency of dumbwaiter accidents is not high, the consequences are serious, while the frequency of lift accidents is high, but its consequences are serious.

Fig. 3

The whole life cycle of an elevator includes the stages of design, manufacture, installation, maintenance, use, disassembly, etc. In this study, the 412 elevator accidents can be categorised under six stages of occurrence: installation, use, maintenance, rescue, reconstruction and disassembly. The statistical results are shown in Table 2.

The statistical results show that the most accidents (n=238) occur at the use-stage, accounting for 57.77% of the total number of accidents, contributing 50.76% of deaths and 82.14% of injuries. Besides, accidents during use, maintenance and installation stages caused the most casualties. It shows that the probability of injury in the use, maintenance and installation of elevators is high, and the protection of personnel in these stages is the top priority of elevator safety technology and management requirements.

To find out the reasons for the frequent accidents in the above three stages, we checked the official accident reports. It is found that the occurrence of elevator accidents in use stage is mainly related to incorrect use of elevators (n=62), improper self-rescue disposal of people trapped in elevators (n=25), inadequate guardians (n=21), unconfirmed status of elevators before use (n=17), elevator failures (n=80) and improper management (n=45). According to the official accident report, during elevator installation and maintenance, unsafe phenomena such as improper operation (n=94, 61.04%) and failure to take effective safety protection measures (n=31, 20.13%) occur from time to time have become important reasons for the frequent occurrence of elevator accidents in these two stages. For example, on August 2, repairman did not open the ‘overhaul’ lever while repairing an elevator, resulting in his death in the elevator shaft by an upward moving elevator in a community in Zhejiang province [10]. On November 26, 2017, during the installation of an elevator in a hotel in Anhui Province, elevator installers failed to follow the installation procedure provided by the elevator manufacturer, and installation was done improperly without protective measures such as scaffolding, resulting in the death of four installation workers [11].

Figure 4 shows the distribution of stages involved in different types of elevator accidents. As shown in Figure 4, the lift accident involves all six stages, whereas the dumbwaiters and escalators (passenger conveyors included) accidents only involve two stages which are use and maintenance, and this is related to the structural characteristics and use-environment of elevators. Compared with lifts, the installation environment of dumbwaiters and escalators (passenger conveyors included) is safer [9], so accidents do not easily occur as easily as in lifts during construction. While in the maintenance and use stages (cases=65, deaths=34, injuries=47), accidents can be caused by inadequate guardian supervision (n=19, 29.23%), improper operation (n=15, 23.08%), equipment failure (n=13, 20.00%), unlicensed work (n=8, 12.31%) and other factors. Therefore, the safety management of dumbwaiters and escalators (passenger conveyors included) should focus on the use and maintenance stages. As for lifts, as shown in Figure 4 and Table 2, the accident occurred during the installation process of lifts is the most serious one, with a death ratio of 0.89, followed by the rescue stage and reconstruction stage, both with a death ratio of 0.86. And the death ratio of accidents in the disassembly stage is 0.75. According to the accident description in our lift accident sample, the high death ratio was caused by falling (n=204). This is because the use environment of lift is generally high-rise buildings, and more safety protection is required in the installation and reconstruction process. When the workers do not take effective safety protection measures, such as not wearing a full-body safety harness, most of them may die in a falling accident [12]. The results show that the accident consequences in installation, rescue, reconstruction and disassembly of lifts are more serious, and emphasis should be placed on these stages in lift safety management.

Fig. 4

To analyse which people are easily injured and killed in elevator accidents, we have made a statistical analysis of the identity of the victims, as shown in Figure 5. The identity statistics of casualties are basically consistent with the occurrence stages of accidents. Individual inconsistent cases are due to non-maintenance or non-installation personnel mistakenly entering the elevator car or shaft during installation or maintenance, and the casualties in such accidents are called others.

Fig. 5

Figure 5 shows the number of casualties is highest for passengers in lift accidents, with the death of 122 people in total and 122 injured in 169 accidents, which is followed by maintainers and installers. Among them, 71 lift accidents resulted in the death of 64 maintainers and 14 getting injured, and a total of 64 installers getting killed and 9 getting injured in 61 lift accidents. In escalator accidents, passengers are also the ones with the largest number of casualties (34 escalator accidents resulted in 41 injuries and 8 deaths). But the statistical results of dumbwaiter accidents are unusual. The results show that dumbwaiter accidents mainly lead to casualties of operators (n=20, 90.91%). This is because dumbwaiters are only used for carrying goods. According to the accident description in the dumbwaiter accidents sample, the main causes of injury or death of operators are due to the illegal ride in dumbwaiters (n=7, 36.84%), improper operations (n=5, 26.32%) and equipment failures (n=5, 26.32%).

The mechanical structure of the elevator is complex, and the operating environment is quite at high altitudes. Thus, there are many types of elevator accidents. According to the official accident reports, these 412 elevator accidents can be classified into five types: fall, extrusion, collision, shear and others (including electric shock, trapped, tumble, winding and reversal), as shown in Table 3.

Table 3 shows that ‘Fall’ occurred most frequently, and caused the largest number of casualties, reaching 244, constituting 46.30% of the total casualties, followed by ‘Extrusion’. The accident death ratios of fall and extrusion were 0.77 and 0.75, respectively, indicating that the fall and extrusion accidents exhibit not only high probability but also serious consequences which are the two major characteristics of casualties in elevator accidents.

The accident type is closely related to the elevator type, such as reversal and winding, and other accident types only occur in the escalator. Therefore, Figure 6 shows statistics on the accident types according to the elevator category. The overall statistical results are consistent with Table 3. However, there are unexpected findings:

Fig. 6

Figure 6 (b) shows that the frequency of winding accidents in escalators is not high, but the consequences are very serious (death ratio=50%). According to [13], the main causes of winding accidents are step or pallets sagging guard damage of escalators, missing steps, or failure of safety devices.

Figure 6 (c) shows that the type of accident with the most serious casualties caused by dumbwaiter is extrusion (n=16, 72.73%), rather than fall, which is related to the function of dumbwaiters. According to the description of accidents, the casualties in dumbwaiter are mainly related to the illegal use of it to carry people (n=7, 33.33%), improper operation (n=6, 28.57%) and equipment failure (n=5, 23.81%).

Figure 6 (d) shows that the electric shock does not often occur in the lift accident types, but the accident consequences are very serious (the only electric shock accident resulted in one death). For trap accidents, there will be no casualties when passengers are trapped in elevators. But in this work, there are two cases in which the accident type is a trap. According to the original data of the two cases, the main reason is the failure of the elevator emergency rescue alarm function, which leads to the delay in emergency rescue, and if the passenger(s) is not found trapped in time, it will result in the injury and death of the trapped passenger(s).

The occurrence of accidents is usually the result of the interweaving and interaction of many factors, but there is still a direct cause [14]. Based on the official accident report, the direct cause of the 412 cases could be divided according to people, equipment and safety management. The statistical results are shown in Table 4.

Table 4 shows that the largest number of accidents is caused by people’s unsafe behaviours, accounting for 60.68% of the total accidents. And nearly 40% of accidents are caused by elevator defects and inadequate safety management. Then, the specific forms of these causal factors in different types of elevator accidents are counted.