# Long-Term Monitored Road Degradation Functions as a Tool to Increase Quality of Pavement Design
## 1 Introduction  
The sustainability of the road network is under ever-increasing economic, environmental and social pressures. Road infrastructure users are demanding higher and higher benefits from road administrators for their private as well as public financial resources. This represents, in particular, a combination of ensuring higher road safety level, acceptable time availability of destinations, but also economic efficiency in the processes of road infrastructure management by administrators. At the same time, new regulations related to environmental protection and efforts to actively implement finance in terms of value for money are constantly emerging. These, as well as other regulations and restrictions, challenge the whole sector to find new or improve existing solutions that have innovative features. Their goal is to move the whole society forward and at the same time in terms of sustainability rules, they will not generate adverse effects for future generations. The general concept of road infrastructure sustainability is well defined and its basic characteristics are recognized worldwide. Nevertheless, there is scope for its partial parts to be modified, while the aim is to ensure a higher quality of the whole model. Among the most important processes within the sustainability model include pavement management systems (PMS). Their task is to optimize the performance of roads during their expected service life and, thus, especially to ensure the time optimization of construction interventions in the road [1, 2]. Achieving this state cannot only bring significant financial benefits, but also reduce the demands on the environment and satisfy the user demand for quality road infrastructure. The starting point for the successful applicability of PMS is the use of pavement performance forecasting model (PPFM) functions. It determines the planned performanceof new roads and the residual life of existing roads, during their life cycle. For these two components of the sustainability model, a mutually complementary relationship applies, where PPFM directly evaluates and expresses the pavement condition in a presentable form. At the same time, all tasks associated with monitoring the condition of roads contribute to the improvement of PPFM. As can be seen from Figure 1, due to its great importance, the pavement performance forecasting model must be able to work efficiently with a large group and several types of data. Due to the different transport, climatic and construction characteristics of the managed road network, these data require their own approaches for collection, processing and, of course, their interpretation. This also applies to their basic part, which they are degradation models of residual road performance. They represent the so-called indicator of road quality [5] presented as a combined mathematical-graphical expression of the decline in road performance over time. The absence or poor quality of these functions greatly weakens the whole meaning of the pavement management system. Administators, without information about the exact development of the road condition in the future, applied maintenance and repair work solely on the basis of the current quality of the road, or made their own estimates of future development based on an expert estimate. This procedure, of course, often led to bad managerial decisions, which were accompanied by low financial efficiency. From this reason degradation models have already become an essential part of the road management system and their regular application can achieve the sustainability of the entire process of repairs, maintenance and reconstruction of the road network [6; 7; 8]. Figure 2 illustrates the general concept of application of corrective pavement treatment as a function of pavement condition. Figure 1: The position of the pavement management system in the general philosophy of the pavement sustainability [3; 4].