IMPROVING SPIRAL GEOMETRY OF EXISTING TRACKS

This paper discusses two problems encountered during planning for field tests of a type of improved spiral, referred to as a K spiral. The first problem is that the spirals selected as test sites have shapes that are so far from the original design shapes that it would not be feasible during routine track lining to bring them back either to their original design shapes or to the corresponding simple K spiral shapes. This problem has been solved by a generalization of the K spiral design method. Illustrations are given of generalized K spiral shapes that are close enough to the existing shapes so that they can be achieved during routine track lining. The second problem was found by computer simulation of movement of an Acela vehicle over a generalized K spiral. Simulation at curve balancing speed predicts that dynamic response to the generalized K spiral will be much better than dynamic response to the corresponding traditional spiral. But, simulation with the vehicle's speed raised to give 9 inches of cant deficiency predicts that dynamic response to the initial choice of generalized K spiral will be worse than dynamic response to the traditional spiral. The generalized K spiral can be adjusted to give performance at 9 inches cant deficiency that is comparable to the performance of a corresponding traditional spiral. For the covering abstract see ITRD E123761.