c. Incorporate behavioral science, training, biology and physiology, human performance and capacity into safety codes and design.


a. Research the state of practice and best practices related to safety systems (e.g., hazard detection, notification, ventilation, fire suppression, emergency egress, and system integration). Develop appropriate minimum safety system requirements to incorporate into national-level guidelines and standards.

b. Compare international underground safety codes and guidelines with those applicable in the United States to identify inadequacies and guide future practice, recognizing existing efforts in this area (e.g., by FHWA).

Underground space can be as safe, attractive, stimulating, functional, productive, and healthy as similar-use surface space. Negative perceptions about underground space, however, can be as difficult to overcome as complex safety and technical challenges. Acceptance and use of underground space may increase with greater convenience and comfort of use (e.g., by incorporating better connectivity among underground systems that limit pedestrian travel time and lengthy vertical movements by stairs, escalators, or elevators). More intuitive understanding of safety in the underground by its occupants will also increase acceptance.

Safety in the underground is achieved by avoiding, transferring, or reducing risks associated with naturally occurring phenomena (e.g., gases, radiation, extreme temperatures, water, and lack of oxygen) and human activity (e.g., fire, smoke, hazardous materials, intentional or accidental explosions, structural failure, or simple human failure). Safety is more challenging with increasing infrastructure complexity. Human factors engineering becomes essential to increasing the ability of people to operate and occupy the underground safely.

Safety codes are often written in response to incidents or litigation and are not flexible enough to accommodate evolving technologies. Safety is created operationally or through technical solutions, but it is dependent on designing and operating beyond mere compliance with often inadequate codes. The few federal-level safety regulations for underground infrastructure mostly apply to construction rather than to operational usage of most facilities. State-level fire safety codes do not fully address underground structures and will likely be inadequate when different occupancy types are combined in one underground space (e.g., public transportation and commercial).

Capital construction and operational risk mitigation costs for underground space can be substantial and could preclude an underground project from being started, or could result in improper system maintenance. Human factors engineering can help to minimize costs associated with avoiding or transferring risk, for example, by identifying ways to reduce risk through safety regulations and education when technological solutions are not feasible. Innovation in design and

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