Evaluation of Sperling’s Index in Passenger and Freight Trains Under Different Speeds and Track Irregularities

The two factors of track irregularity and train speed affect the dynamic behavior of rail vehicles and can lead to an increase in dynamic forces, a decrease in ride comfort, and derailment in some cases. In this paper, the effect of train speed increase and different conditions of track irregularity on ride comfort and ride quality are investigated. For this purpose, first, two freight and passenger train models have been modeled in UM software, and then the effect of train speed increase and track irregularities (different US federal classes) have been studied with Sperling’s index. A freight train with the model of 18-100 and 3-piece bogie and a TGV high-speed train with 10 wagons were simulated. The results showed that in Sperling’s index, with the increase in the train speed and irregularity amplitude, the value of ride comfort and ride quality generally increased. For example, in the passenger train and irregularity classes 5 and 4, with the increase in train speed from 10 to 100 m/s, the Sperling’s index values changed from 0.66 to 1.99 and from 0.78 to 2.25, and increased 200% and 188%, respectively. In other words, at a speed of 10 m/s, passengers' comfort is just noticeable, while at a speed of 100 m/s and class 4, the situation is more pronounced but not unpleasant and the system should be monitored.