Given the high volume of people using today's public transportation systems, passenger safety has taken on even greater importance in engineering design. This trend has also driven more technical innovation to achieve the same levels of safe ridership using less energy and with reduced cost. Jet fans are ideal mechanical systems for emergency ventilation of unidirectional road tunnels; the arched roadway tunnels provide ample space for installation, and this equipment can he operated to transport smoke in the direction of traffic flow - thus enabling stranded motorists to evacuate under clear air in the opposite direction. The application of jet fan systems to multidirectional rail tunnels is not as straightforward, but it can produce significant savings in terms of both energy usage and capital cost, without diminishing passenger safety. The purpose of this paper is to demonstrate how jet fan systems can be applied to rail tunnel networks as mitigating factors against traditionally large, expensive and high energy-consumption fen facilities. This paper covers the key aspects of jet fen implementation - including spatial allowance, operational modes, high-temperature exposure and economic impacts -through presentation of a sample rail tunnel network and analysis of hypothetical emergency ventilation scenarios.
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