This work introduces the design, architecture, implementation, and testing of a low-cost and machine-learning-enabled device to be worn on the wrist. The suggested wearable device has been developed for use during emergency incidents of large passenger ship evacuations, and enables the real-time monitoring of the passengers’ physiological state, and stress detection. Based on a properly preprocessed PPG signal, the device provides essential biometric data (pulse rate and oxygen saturation level) and an efficient unimodal machine learning pipeline. The stress detecting machine learning pipeline is based on ultra-short-term pulse rate variability, and has been successfully integrated into the microcontroller of the developed embedded device. As a result, the presented smart wristband is able to provide real-time stress detection. The stress detection system has been trained with the use of the publicly available WESAD dataset, and its performance has been tested through a two-stage process. Initially, evaluation of the lightweight machine learning pipeline on a previously unseen subset of the WESAD dataset was performed, reaching an accuracy score equal to 91%. Subsequently, external validation was conducted, through a dedicated laboratory study of 15 volunteers subjected to well-acknowledged cognitive stressors while wearing the smart wristband, which yielded an accuracy score equal to 76%.

The evacuation and abandonment of large passenger ships, involving thousands of passengers, is a safety-critical task where techniques and systems that can improve the complex decision-making process and the timely response to emergencies on board are of vital importance. Current evacuation systems and processes are based on predefined and static exit signs, information provided to the passengers in the form of evacuation drills, emergency information leaflets and public announcements systems. It is mandatory for passengers to wear lifejackets during an evacuation, which are made of buoyant or inflatable material to keep them afloat in the water. Time is the most critical attribute in ship evacuation and can significantly affect the overall evacuation process in case passengers do not reach their embarkation stations in a timely manner. Moreover, extreme conditions and hazards, such as fire or flooding, can prevent and hinder the timely evacuation process. To improve the current evacuation systems onboard large passenger ships, a smart lifejacket has been designed and implemented within the context of the project SafePASS. The proposed smart lifejacket integrates indoor localization and navigation functionality to assist passengers during the evacuation process. Once the passenger location is calculated within the ship, the navigation feature guides the passengers along an escape route using vibration motors attached to the lifejacket. This is done in the form of haptic cues to help passengers reach their destination, especially in low-visibility conditions and in case they are left behind or lost. This can increase passenger safety and reduce the total evacuation time, as well as support dynamic evacuation scenarios where the predefined routes and static exit routes may not be available due to fire or flooding incidents.

Evacuating large passenger ships is a complex and safety-critical process. During an evacuation, the passengers are assisted by exit signs, the public announcement system and the crew, the latter providing instructions for mustering and abandonment. In addition, passengers are required to wear lifejackets that are made of buoyant or inflatable material used to keep them safe in the water. The timely mustering and guidance of passengers to their embarkation stations is of the utmost importance and greatly affects the evacuation time in the case of an emergency. This is especially important in extreme conditions and hazards, such as fire and flooding. Within the context of the project SafePass, a smart lifejacket is designed and implemented, which integrates indoor localization technology and a haptic navigation system that can assist passengers during evacuation. The indoor localization technology reports the passengers’ location within the ship, while the navigation system can negotiate a route and navigate the passenger using vibration motors attached to the smart lifejacket. These actuators vibrate to provide haptic cues to the passenger to navigate them to their destination in low visibility conditions and in the case they are left behind or lost. The smart lifejacket can also help the crew to locate stray passengers, thus increasing the safety of passengers and reducing the evacuation time as a whole.