sustainability Article Influence of Evacuation Walkway Design Parameters on Passenger Evacuation Time along Elevated Rail Transit Lines Using a Multi-Agent Simulation Zihua Pan 1,2,* , Qingchao Wei 1, Olav Torp 2 and Albert Lau 2 1 School of Civil Engineering, Beijing Jiaotong University, Beijing 100044, China; [email protected] 2 Department of Civil and Environmental Engineering, Norwegian University of Science and Technology, 7491 Trondheim, Norway; [email protected] (O.T.); [email protected] (A.L.) * Correspondence: [email protected]; Tel.: +86-152-0134-3069 Received: 30 September 2019; Accepted: 29 October 2019; Published: 31 October 2019 Abstract: Passenger evacuation on elevated railway lines has always been an important issue for elevated rail transit safety management, because it is challenging to evacuate passengers efficiently in the event of man-made calamities and natural disasters. Therefore, an evacuation walkway has been designed as a primary solution to assist passenger evacuation during an emergency on elevated rail transit lines. However, investigations on how evacuation walkway designs influence passenger evacuation time are still limited. This study established two evacuation scenarios of interval evacuation on elevated rail transit lines and put forward a new evacuation time measurement method, based on the concept of ‘evacuation time for passengers leaving the evacuation walkway risk zone’. Then, the evacuation time for 90 combinations of entrance widths and walkway widths was simulated by a multi-agent evacuation simulator, Pathfinder, considering 1032 passengers being evacuated both unidirectionally and bidirectionally. The results show that the entrance width and walkway width have a combined effect on passenger evacuation time. An increase in the walkway width from 0.7 m to 1.5 m may potentially reduce the evacuation time by 54.5% in unidirectional evacuation, and 35.2% in bidirectional evacuation. An increase in the entrance width results in a noticeable evacuation time fluctuation when the walkway width is 0.7 and 0.8 m for both evacuation scenarios, while in a bidirectional evacuation, a noticeable fluctuation also can be observed when the walkway width is within the range of 1.4–1.5 m. According to the study, a potentially good design parameter combination for a newly built evacuation walkway is 1.3 m and 1.4 m for the walkway width and entrance width, respectively. The findings from this study may provide a useful reference in the optimization of the design of evacuation facilities and improvement of passenger evacuation safety in rail transit systems. Keywords: passenger safety; Maglev transit; evacuation time; multi-agent simulation; evacuation walkway; parametric design 1. Introduction Due to the increase in man-made accidents and natural disasters, passenger evacuation in a rail transit system has became a more prominent research issue for emergency response planners, transport engineers and policymakers [1–6]. It is challenging to evacuate a mass volume of passengers in a well-organised and highly-efficient way in a rail transit system because of the uncertainty of accidents and complex nature of individual characteristics [7–9]. Passenger evacuation in rail transit systems can be hard to predict, because the types and locations of accidents that occur in rail transit are unpredictable [10]. In many cases, passengers are required to evacuate quickly in a difficult-walking Sustainability 2019, 11, 6049; doi:10.3390/su11216049 www.mdpi.com/journal/sustainability Sustainability 2019, 11, x 6049 FOR PEER REVIEW 22 of of 18 17 walking environment, e.g., through a tunnel with low visibility or a viaduct with limited walking spaceenvironment, [11,12]. 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