Some metro lines are considering more efficient ventilation schemes. Ideally, filtered fresh air is introduced at the beginning of a tunnel and the air is extracted at the other end before the next station is reached. In effect, the air is moved by the piston effect of the running trains. This also removes some of the braking heat trapped within the system. In Vienna, for example, the metro line operates a ventilation system that forces as many as three air changes per hour for each running tunnel section between two stations; in some stations the supply and the exhaust air is filtered. This is vitally important, as the multi-layer underground railway network consists of five, mostly underground, routes that cross over in the stations on different levels every three to five minutes. As a result, large number of braking and accelerations oc- cur creating large amounts of railway dust in the tunnels, stations and BUSINESS FOR SALE Business Opportunity in beautiful Truckee, California. Dennis Dodds & Associates, Inc. was established in 1982 by the current owner. The firm is full service offering Residential Design, Structural, and Civil Engineering services with a well – established customer base and excellent location. Located in the beautiful Sierra Nevada Mountains, Truckee is surrounded by world class skiing and is renowned for its year round outdoor activities. The housing industry is strong, as Truckee has become a targeted destination for high earners able to work remotely. There is a mix of high end new construction and thousands of vacation homes in need of updates. Owner financing available. If interested or would like further information, please Email Dennis at email@example.com.
neighboring equipment rooms. Consequently, the tracks are cleaned during night shifts by a mobile tunnel cleaning train. Some European lines started looking at improvements to their tunnel fan systems as well. Advances in the design and construction of more energy-efficient fan systems have come a long way and are comple- mented by new filtering systems that more efficiently capture dust particles in the air. The fan systems in the U.S. would likely follow the same path, but this will take time. In Europe, the energy is more expensive and urban metro lines have been forced to devise more sus- tainable, energy-efficient solutions that are easier to maintain. Driverless-train systems would likely become inevitable in the years ahead and could ultimately have the greatest impact on the micro-dust problem. Metro lines in Vienna, Hamburg, and Paris have already made significant investments in driverless systems that incorporate platform screen doors at each station. In addition to contributing to lowering the air dust at stations and its impacts on passengers, the screen door systems provide for much safer rail operation as they significantly lower risks of accidents. A driverless train can stop within a tenth of an inch of its destination, enabling the glass front to maintain a seal as the screen door opens. Phased Approach. Regardless of the approach to minimizing micro- dust in a rail tunnel setting, periodic maintenance cycles can provide owners with an opportunity to incorporate a phased, yet sustainable so- lution. By doing so, they can minimize the initial financial impact and achieve gradual improvements to air quality for workers and patrons while enhancing safety and lowering maintenance costs. BERND HAGENAH is principal engineer on HNTB’s National Tunnel and Underground Team, has a background in physics and a doctoral degree in mechanical engineering. Hagenah is based in the firm's New York City office and serves as an accomplished resource to the firm's clients and projects across the nation. Hagenah is internationally known as one of the world's top technical experts and thought leaders in tunnel ventilation and aerodynamics. He previously served as senior consultant and international project manager for another tunnel consulting firm in Switzerland. HNTB’s tunnel ventilation practice has subject matter experts in rail aerodynamics, fluid dynamics, and rail-facility systems operation and integration; they are located in Seattle, Oakland, and New York.
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