North American turnout and special trackwork design has evolved in an operating environment in which axle loads have increased significantly but operating speeds have remained modest. Consequently, while trackwork components have become much more robust, turnout geometries and overall system design has remained essentially static for many decades. Implementation of high speed rail (“HSR”) in North America will necessitate a radically different approach to turnout engineering. While there is much to be learned from European and Asian experience with high speed, it is anticipated that vehicle designs and mixed freight access will result in much greater axle loads. The combination of operating speed and loading will present unique challenges. Critical design elements for North America’s new generation of HSR turnouts will include: a) Compound geometries to optimize ride quality and safety while keeping overall lengths within manageable limits. b) Fastening and horizontal support systems to withstand high dynamic lateral loads. c) Dampening systems to attenuate high frequency vibration. d) Detailing such as rail seat canting and kinematic gauge optimization to enhance ride quality and increase component life. e) High modulus vertical support systems. f) Drive and locking systems specifically tailored to long HSR layouts. Regulations governing the layout and maintenance tolerances of North American turnouts will also have to be re-examined with the advent of high speed rail. Complex geometries and rapid transient loading will render the conventional approach of limiting speeds based on calculated imbalance ineffective. Accurate and rational assessment of operating safety will demand the application of dynamic numeric modeling to the entire vehicle / turnout system.

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