Experimental study on individual walking speed during emergency evacuation with the influence of ship motion

Highlights

• The impact of ship motion on human walking speed was experimentally investigated.

• The ship’s rolling motion reduced the normal walking speed by 3.8%–10.3%.

• The farther away the rolling centre is, the smaller the human walking speed.

• The athwartship fast walking speed was 0.8%–4.9% faster than fore-aft fast walking.

• During voyage, the reduction ratio of the human walking speed was 86.0%–96.2%.

Abstract

Ship motion is an important influencing factor in passenger ship evacuation that affects the entire evacuation process by reducing an individual’s walking speed. This study aims to quantify such effects in ship berthing and sailing operations by collecting experimental data to support passenger ship evacuation decisions. The study utilized Dalian Maritime University’s training ship to conduct human walking experiments to study the influence of ship motion on passengers’ normal and fast walking speeds. It was found that during the berthing period, an individual’s normal walking speed was 1.28–1.68 m/s, and the fast walking speed was 1.50–2.14 m/s. During the sailing, the ship’s rolling motion reduced the normal walking speed by 3.8%–10.3% and the fast walking speed by 3.7%–14.0%. Due to the influence of ship rolling, the higher the deck and the farther away the rolling centre is, the smaller the athwartship and fore-aft walking speeds. Athwartship walking was slightly faster than fore-aft walking. Similarly, in the normal walking mode, the athwartship walking speed was 1.6%–3.7% faster than fore-aft walking, while in the fast walking mode, the athwartship walking speed was 0.8%–4.9% faster than fore-aft walking. Furthermore, during the berthing period, the average walking speed of the younger group was 24.1% higher than that of the older group. Finally, during the sailing, the speed reduction ratio of an individual’s walking speed was 86.0%–96.2%, and the value decreased as the deck height increased.

Introduction

Passenger ships are an important part of the maritime transport industry, and their importance grows in recent years, given that the large cruise vessel market has been rapidly developed [1], [2]. Although serious accidents involving passenger ships are rare, possible consequences can be catastrophic [3], [4]. This has been demonstrated by the accidents in history, such as the sinking of Ro-Ro passenger ship “Sewol” near Screen Island in 2014, which caused the loss of 304 passengers and crew, including 8 dead or missing [5], [6]. In an accident of this kind, the effective evacuation of passengers is the last resort to reduce loss [2], [3], [7]. Existing evacuation analyses do not always meet a satisfactory level; the accidents of the high-speed passenger catamaran “St. Malo” and the cruise vessel “Costa Concordia” are illustrative examples [7], [8]. Some researchers argue that if the effects of ship motion and listing on personnel behaviour are not taken into account, evacuation analysis may be less realistic to provide appropriate evacuation guidance [7], [8], [9].

An individual’s walking speed is crucial for safety evacuation analysis as it greatly affects the results [10]. In the study of land-based evacuation, experiments on an individual’s walking speed have been carried out extensively [11], [12], [13], [14]. On ships, an individual’s walking speed depends not only on the age, gender, height, and mobility of passengers but also on external factors, such as ship motion and listing [6], [10], [15]. As shown in Fig. 1, a ship will oscillate in six degrees of freedom in the ocean, with the most common motions being roll and pitch. Since the length of a ship is larger than its width, in general, its roll is greater than its pitch [16], [17]. The impact of ship motion on an individual’s walking speed is so obvious that those with experience onboard have observed that the “swing gait” of seafarers will continue for a while after returning to the land [18]. Also, at a specific ship rolling angle ($\theta$), the farther the distance (D) from the ship rolling centre, the greater the roll amplitude (radian) is, as shown in Fig. 2. Therefore, under normal circumstances, a ship’s bridge rolls more than its engine room. In the process of ship rolling motion, to maintain body balance, people in different positions of the ship must adjust their posture or gait, which will affect their walking speed.

In this study, to understand the influence of ship motion on an individual’s walking speed, a series of experiments were conducted on the training ship “Yupeng” of Dalian Maritime University, China. The experimental data, including that during berthing and sailing, was collected and used to analyse the degree of influence of ship rolling motion on an individual’s walking speed, the difference between athwartship and fore-aft walking speeds, the relationship between normal and fast walking speeds, and the walking speed difference between different decks. The findings provide useful insights to support, expand, and verify the existing and/or newly developed passenger ship evacuation models and simulation software. Furthermore, they also provide reliable experience data that can help crowd management during passenger evacuation.

This study was conducted under natural conditions, however, it was not possible to fully control the ship motion and weather conditions which inevitably reduced the level of control (i.e., ship rolling angle) over the experiment. However, reducing the experimental control is helpful to understand an individual’s walking speed under the real ship motion, which is very effective in solving real problems [17].