Title

INCREASING SPEEDS THROUGH THE DIVERGING ROUTE OF A TURNOUT WITHOUT INCREASING LEAD LENGTH

Document Type

Journal Article

Publication Date

2004

Subject Area

planning - route design

Keywords

Wear, Turnouts, Speed, Simulation, Ride quality, Performance, Optimization, Optimisation, New Jersey Transit, Geometry, Computer simulation

Abstract

Presented are the results of Phase I of an FRA-sponsored study on low-cost means to increase safe speeds through turnouts by way of a retrofit or upgrade. Turnout lead length and frog angle were considered fixed, eliminating costs in relocating the frog or switch points. After in-depth research and dynamic simulation testing, it was determined that the best approach was to optimize existing American Railway Engineering and Maintenance of Way Association (AREMA) turnout geometry. This required a new diverging switch rail and reshaping both the curved stock and closure rails. This low-cost modification applies to most existing turnouts and is expected to improve ride quality and decrease wear without detriment to current maintenance practices. The optimization of a conventional AREMA #20 turnout with straight switch points is discussed as an example. The best vehicle performance in simulations was achieved by a design having a very low entry angle. Vehicle behavior at a speed of 51 mph was significantly improved over the AREMA straight point design at its speed limit of 36 mph, as well as that of the AREMA curved point design at its limit of 50 mph. Also, simulated vehicle performance was nearly as good as for a #20 tangential turnout that has a 20 ft longer lead length. Finally, there was improved performance at speeds as high as 60 mph without exceeding any established safety limits. From these results, a turnout with the reshaped geometry has been constructed and is scheduled for installation on New Jersey Transit.