MEASUREMENT OF VERTICAL TRACK MODULUS FROM A MOVING RAILCAR

Track performance and maintenance requirements are strongly related to track modulus – the ratio between the rail deflection and the vertical contact pressure between the rail base and track foundation. This work seeks to develop an on-board, real-time, non-contact track modulus measurement system that functions at track speed. Measuring track modulus from a moving rail car is nontrivial because there is no stable reference for the measurements. The proposed system is based on measurements of the relative displacement between the track and the wheel/rail contact point. A laser-based vision system is used to measure this relative displacement. Then a mathematical model is used to estimate track modulus. This paper addresses new findings as a continuation of the University of Nebraska-Lincoln and Federal Railroad Administration research presented at AREMA 2005. These new findings include recent system upgrades and hundreds of miles of new test results from revenue service. System upgrades include a new passive loading vehicle, a simplified calibration system, and the real-time processing of data. Results are presented from field testing in revenue service at different locations, on various types of track, and in different weather seasons. In addition, the effect of speed is analyzed and special track transition