###### Abstract  
Introduction: Subway-pedestrian collisions are a significant and growing problem, but they are poorly understood. This study presents the first subway-pedestrian collision model with the aim of evaluating the baseline safety performance of an R160 NYC train and track combination and the potential safety effects of drainage trough depth. Methods: A baseline simulation test sample of 384 unique impacts (8 velocities (2-16 m/s), 24 positions (standing jumping and lying), and 2 track types (flat and crossties)) was created in MADYMO. The full simulation test sample (N = 1920) included with various depth drainage troughs (0-1 m). Head injuries and wheel and third rail contacts were evaluated. Results: Limb-wheel contact occurred in 60% of scenarios. Primary and secondary contact HIC\({}_{15}\) showed similar high severity, with an HIC\({}_{15}\) < 2000 (88% risk of AIS 4+) in 29% of results for both train and ground contact. Impact velocity strongly influences primary contact HIC\({}_{15}\) with limited effect on secondary contact. Impact velocities between 6 and 16 m/s showed little change in wheel contact. Increasing the trough depth up to 0.5 m showed a decrease in wheel contact probability with little increase in secondary contact. No further benefits were found above 0.5 m. Conclusions: A subway-pedestrian collision model is presented which predicts that wheel-pedestrian contact risk can be reduced with a 0.5 m drainage trough. The model suggests that slower impact velocities may reduce head injury risk for primary contact; however, this will have less effect on injuries caused by secondary and wheel contact. pedestrian safety; multibody modelling; head injury risk; subway train; rail safety; simulation +
Footnote †: journal: Applied sciences  
from full-scale vehicle impact tests involving either a human dummy or a Post-Mortem Human Surrogate (PMHS), e.g., [16; 17; 18], can be used for model validation. Optimum impact parameters to reduce pedestrian risk have been evaluated using Multibody Modelling (MB), Finite Element (FE) modelling, or coupled FE and MB models, e.g., [19; 20; 21]. Weighted injury costs from multibody injury criteria have been used to assess the effects of vehicle shape and braking on pedestrian injury outcomes [22]. A major challenge in replicating this approach for subway safety is the cost of physical impact tests. Automotive pedestrian ground contact typically involves interaction with a flat surface [2; 20; 23]. Recent street-level tram-pedestrian collision studies utilize flat surfaces for secondary impact [24], or focus only on primary contact injuries [25]. In contrast, secondary contact for subway-pedestrian collisions involve a more complex geometry with different track types. These tracks introduce new dangers such as live electrically charged running rails (third rail), sharp corners, and drainage troughs, which may affect kinematics and run-over risk. Drainage troughs (sometimes colloquially referred to as \"suicide pits\") are channels between the tracks allowing for extra space such that an individual may avoid contact with the train's undercarriage or wheels. Recent analysis of NYC incident reports shows a substantial number of cases with incapacitating injuries including amputation, likely resulting from wheel contact [26]. First used in the London Underground in 1932 [27], drainage troughs are present in many subway systems worldwide. Multiple analyses [28; 29; 30] of the effect of drainage show that troughs show lower fatality rates in stations featuring them. However, a recent paper showed a decline in references to these troughs since 2007 [31]. While empirical evidence suggests that drainage troughs may act as a viable countermeasure in reducing fatality rates, the results of such studies were unable to attribute the reduction in fatality rates to drainage troughs due to the presence of confounding factors [32].