# Influence of the Analytical Segment Length on the Tram Track Quality Assessment
## 5 Conclusions  
The track geometry quality assessment can be performed in two ways, by comparing the individual measured values of the track geometry parameters concerning the allowable tolerances or by calculating the TQI along the track segment of a specific length. The established TQIs are mainly intended to assess the track geometry quality for high-speed and conventional standard-gauge railways and broad-gauge railways, where track geometry data are collected by track recording vehicles in loaded track conditions. They are commonly calculated as standard deviations or average or weighted values over a 200m long track segment. A comparison of the five narrow-gauge tram-track geometry parameters recorded on the Osijek tram network with a manually operated trolley in unloaded track conditions with the prescribed permissible tolerances defined for measured values collected in loaded track conditions showed that the measured values of individual tram-track geometry parameters are significantly lower. This is especially true for horizontal alignment and longitudinal levels, where the application of prescribed tolerances in track quality assessments could lead to the conclusion that the track quality is good or that these parameters do not affect the calculated value of TQI. Additionally, the heterogeneity of tram-track geometry degradation influential factors cannot be adequately considered by analyzing the fixed 200m long track segments. From the above, several questions arose: (1) how to assess the tram-track geometry quality by using measurements collected in unloaded track conditions; and (2) whether and how a change of the analytical segment length affects the track geometry assessment. The goal of the investigation presented here was to answer these questions by performing the track quality assessment on the Osijek tram network using two essentially different TQIs, W and J indices. The calculation of the W index was based on the ratio of geometric values that exceeded permissible tolerances. Permissible tolerances (explicitly defined for this investigation as Alert Limits) were established in coordination with the tram track manager and considering the experience gained with track geometry quality analysis of tram networks with similar characteristics. The calculation of the J index was based on weighted standard deviations of track geometry parameters. Both TQIs were calculated for the entire 27.5 km of operational narrow-gauge tram track on consecutive 200-, 100-, 50-, and 25m-long analytical track segments. The following conclusions were made:  
1. Track segmentation has a significant role in assessing the tram track quality based on track geometry deviations or irregularities and planning track maintenance or reconstruction;
2. By reducing the length of the analytical segment, the resolution of the tram-track geometry quality analysis grows, which means that it is possible to determine the sections of the tracks with insufficient quality more precisely by increasing the number of the analytical segments;
3. Both TQIs can be effectively used for tram-track geometry quality assessment. However, the W index, based on a weighted value of geometry deviations over an analytical segment, is less sensitive to a reduction in the segment length than the J index based on the standard deviation of geometric parameters-the decrease in the analytical segment length enlarges the number of segments with extreme values of W. At the same time, the J value uniformly decreases;
4. The segmentation process must be aligned with the tram track maintenance and reconstruction procedures. It should consider the following aspects affecting the choice of analytical segment length: which track repair/reconstruction technology will be applied; the allocated funds; and how the planned work will impact public and personal traffic along with the track segments.