Report: Safety Framework for the European Hyperloop Network

This article gives a brief summary of the report on hyperloop safety written by Delft Hyperloop. For the full report, click the button below!

Safety is the most important criterion for passenger transportation and thus the hyperloop. The hyperloop is a new mode of transportation with the potential to solve challenges currently faced by the transportation sector. Airports are reaching expansion limits and railways are becoming congested. Furthermore, passenger transportation contributes significantly to global warming. Vehicles in the hyperloop, called pods, travel through near-vacuum tubes and levitate through the use of (electro)magnets. The magnetic levitation and low-pressure environment greatly reduce the drag experienced by the pod. The hyperloop is therefore able to reach speeds over 1000 km/h while consuming minimal energy.

Introduction

For a new mode of transportation, such as the hyperloop, to be feasible and accepted by the public, its safety must be analyzed and proven during the development phase. Currently this has not yet been done in a sufficient degree and shared publicly. This report aims to create a top-level safety concept for the European hyperloop network. As the hyperloop presents itself as a sustainable alternative for short to medium-haul aviation, a high safety target needs to be pursued. This results in the following safety target:

The European hyperloop system shall have at least the level of safety of European commercial airlines in terms of passenger fatalities per passenger kilometer.

An extensive framework focused on prevention, mitigation and intervention is used to reach the hyperloop safety target. Extensive analyses are performed to create a complete and cost-effective safety system. The implementation of appropriate safety measures will ensure all safety goals are achieved. This report uses the general hyperloop system to assess safety and refrains from using specific design choices, thereby allowing all hyperloop parties to use the results, iterate on the assessments and accelerate the development of the hyperloop.

Safety concept

To achieve the envisioned safety target, an elaborate safety system must be implemented in the hyperloop. In collaboration with industry experts, various safety issues have been analyzed. A few critical components of the safety system will be discussed, including fire safety, the communication system, perceived safety and emergency evacuation.

Fire safety

Hyperloop pods travel at high speeds through near-vacuum tubes. The low pressure environment prevents fire from breaking out in the tube. Where possible, subsystems with an increased fire hazard can be located inside the near-vacuum environment, thereby limiting the available oxygen. However, inside the pods themselves, fire and smoke pose a significant threat. The sealed-off nature of the pods further increases the fire hazard. Several safety measures can be implemented to reduce the occurrence and impact of fires.

If a fire breaks out despite the preventive control measures, various safety measures are implemented to mitigate the impact. A water mist system uses fine water sprays to cool the flames and surrounding gases. Moreover, oxygen is displaced through the process of evaporation. The batteries are placed inside compartments with a halon-gas system. This system floods the compartment with fire suppressing agents when a dangerous situation is detected.

Communication system

The autonomous pods of the hyperloop are in constant communication with each other, the control center and the outside world. All this information is transferred using the communication system. A Light Fidelity, or Li-Fi, system is proposed to handle the data communication inside the hyperloop system.

The speed and closed-off environment of the hyperloop create challenges for the communication system. Due to the high speeds, pods often switch between communication cells. This process is called a handover. A high frequency of handovers increase the chance of handover failure, resulting in a temporary communication loss. The communication system should therefore have reliable handover capabilities. Furthermore, the steel tube prevents wireless signals from reaching the pod. To circumvent this problem, the communication system combines both wired and wireless solutions.

The optical spectrum offers an almost unlimited bandwidth at extremely high speeds. Optical wireless communication uses this spectrum to transfer data at short-to-medium range distance. Light Fidelity is proposed as the optimal communication technology. Li-Fi rapidly modulates the intensities of light sources, such as LEDs, to transmit a binary signal. Photodetectors pick up this signal and convert it to data. This creates a high speed and low latency communication system.

Reliable hyperloop communication is ensured by using Li-Fi. However, the information should also be protected from external threats. Safety measures to improve the cyber-security will therefore need to be implemented. By using separate networks for entertainment, information and safety purposes, the system-critical data is shielded. The installation of optical fibers along the infrastructures prevents hackers from physically intercepting communication signals.

Perceived safety

The hyperloop is a new mode of transportation using revolutionary technologies and automated vehicles. For this mode of transportation to be widely used, the acceptance of these technologies is crucial. Design choices and safety measures can be used to increase the level of perceived safety and thus positively influence the acceptance of the hyperloop.

Providing passengers with information about the hyperloop increases the trust in the system. In turn this will make the hyperloop more approachable to the general public and increase the acceptance to use it. The information can be supplied to the passengers through information screens and voice assistants. The design of the hyperloop can be used to increase the feeling of safety by designing the interior to be as spacious and open as possible, within the constraints of the hyperloop system. Furthermore, light colors, comforting round shapes, visible safety features and elements that connect the passenger to the outside world can be used to improve perceived safety.

The automated pods function without on-board staff. In current modes of transportation, personnel performs many tasks besides operating the vehicle. Examples include informing passengers, communicating with the control center and assisting during emergencies. Safety measures such as emergency intercoms, a closed-circuit television (CCTV) system and a reliable communication system will be implemented to take over the role of on-board staff and optimize pod safety.

Emergency evacuation

The hyperloop uses a controlled and low-pressure environment to offer reliable and energy-efficient travel. The controlled environment is maintained by a steel tube with a limited number of exits. Emergency evacuation is therefore more difficult compared to other forms of guided transportation. The concept of combined evacuation, with pod and in-tube evacuation, is proposed to ensure safety during emergencies.

Emergencies can be classified under either in-pod or brick-wall emergencies. In-pod emergencies threaten the safety of passengers in a pod but do not affect the functionality of the system. During an in-pod emergency, pods should reach an emergency exit as quickly as possible. Implementing internal safe havens at regular intervals ensures passengers can evacuate the pod in an efficient manner. Brick-wall emergencies prevent pods from reaching their destination. Furthermore, pods are unable to reach the nearest safe haven. For passengers to safely exit the hyperloop system during brick-wall emergencies, in-tube evacuation is used. This method of evacuation requires a locally pressurized tube through which passengers can walk towards the nearest emergency exit. Nearby pods can pick up passengers to speed up the evacuation process.

Combined evacuation enables emergency evacuation at all times by joining internal safe havens and in-tube evacuation into one concept. Moreover, combined evacuation limits the additional infrastructure that is necessary. Combining this concept with an elaborate evacuation plan will allow passengers to swiftly exit the system and thus ensures safety during emergencies.

Conclusion

This safety framework looks at safety from various angles. Using the outcomes of the analyses, safety measures have been bundled into three safety packages: the recommended, additional and maximum package. A net risk assessment has been performed to analyze the effectiveness of these packages. From this analysis, the recommended safety package with the addition of electromagnetic shielding proved to reduce the risks in the hyperloop significantly and achieve the safety target as set by Delft Hyperloop.

Safety is a complex topic and an integral part of the hyperloop system. This report contains the first publicly shared concept for the hyperloop safety system. However, many topics beyond the scope of this framework still have to be looked at or analyzed in greater depth before the hyperloop will be approved for passenger transport. Examples of these topics are simulations of fire inside the pod to determine the available safe egress time, an assessment of the emergency exit frequency and a more in-depth scenario analysis. The recommendations can be used to improve the safety concept and thereby speed up the creation of a safe hyperloop system.

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