# Influence of the Analytical Segment Length on the Tram Track Quality Assessment
## 1 Introduction
Both approaches resulted in segments of variable length along the network. Newer studies have suggested that the decision on track segment length needs to be based not only on the track technical parameters but also on the economic and operational aspects of track maintenance [19]. Many cities worldwide that have retained the traditional tram systems dating back to before the First World War are trying to upgrade their maintenance procedures by introducing TQIs. However, they are facing several problems. The main one is documenting the tram infrastructure in digital databases, which is the prerequisite for any effective track segmentation, geometry evaluation, and maintenance planning. In addition, the actual knowledge of the track condition is limited to a small number of maintenance employees, and most of them do not have any tools for collecting, systemizing, and integrating the data covering the design, construction, operation, and further maintenance of the tracks. Such data could be stored in databases which would provide data for conducting the assessment of the track quality and maintenance needs [20; 21]. Operators of most European urban rail systems carry out the track geometry quality assessment based on controlling the individual measured values of track geometry parameters concerning the permissible values prescribed by internal regulations [22]. Such is the case with tram operators in the Republic of Croatia, ZET in the City of Zagreb, and GPP in the City of Osijek. Both operators control the quality of the tram track by using the same internal regulations, where only the most significant permissible deviations of track geometry parameters immediately after track construction and before reconstruction are defined [23]. Applying the best practices of the track quality evaluation established for classic ballated rail on tram networks would be most desirable. However, the procedures described in the literature [13; 14; 15; 24] cannot be applied to tram tracks. The main reason for this is the questionable cost-effectiveness of procuring sophisticated track-recording cars for small tram networks consisting of only a few tens of kilometers of tracks. If the measurements are executed with manual tools, such as measuring rods or by manually operated track geometry trolleys, i.e., in unloaded track conditions, the maximum permitted values of the TQIs cannot be utilized. The other reasons are significant differences in track design requirements and exploitation conditions (the track location, geometry design parameters, construction elements, vehicles, and traffic characteristics) between the tram and conventional ballasted rail tracks [22], defined as the critical geometry degradation influential factors [5; 6]. These differences are primarily the consequence of small distances between the tram tracks and the surrounding facilities and requirements for the rational use of urban traffic areas. These requirements often include narrow-gauge tracks, tight horizontal curves of only 18(20) meters' radius, and a lack of transition curves and cant. For this reason, the tram vehicles are of smaller dimensions and weight (the tram axle load is usually twice as small) and with different undercarriages than conventional trains. The latter is particularly pronounced in the case of modern low-floor terms. The differences are also reflected in the tram traffic-flow characteristics given the movement priority and speed. Tram speed is low and very variable along the route due to the small stop distance. Such distances usually vary from 250 to 500 (800) meters, and include crossings where tram vehicles do not have priority to pass. Additionally, due to a lack of space in the densely built-up urban centers, trans often must share the lanes with road vehicles and therefore adjust (primarily reduce) their speed [25]. For the same reason, the tram tracks' superstructure is often built on continuously reinforced concrete slabs, with continuously welded grooved rails enclosed in pavement construction [26].