Deterioration of the railway structure of ballasted tracks is unavoidable and can result in extensive costs for the track owner. Since the railway is one of the most important infrastructures and transport systems it has to be maintained and in order to foresee the deterioration of the track; the phenomena has to be understood and described in an engineering way. Through the years a lot of research has been carried out and a lot of different models have been formulated.

The aims of this work are to present a ‘state of the art’ overview of existing track deterioration models and their properties and, with the models as a base, put together a model that predicts average deterioration cost for different vehicle types. Relations between track-vehicle parameters on one hand and wear and rolling contact fatigue (RCF) on the other are investigated through simulations. Finally, a computer software package is designed as to implement a model proposal to track deterioration.

For the understanding of track deterioration it is necessary to link vehicle properties – mainly forces – to the process of deterioration. Though other factors such as time and environment also affect the track construction, it is the traffic that causes much of the damage. In this report four main mechanisms are considered: (1) deterioration of the track geometric quality due to settlement; (2) component fatigue; (3) wear of rails and (4) rolling contact fatigue of rails.

The literature survey resulted in description and evaluation of a total of 21 models for track deterioration and some models for allocation of costs on vehicles for track access charging purposes. Only a few models tried to describe a more complex picture, involving several parameters and mechanisms. It is further concluded that most models dealing with settlement takes the load to a power between 1 and 5.

Based on the literature survey a model proposal is presented that could be used to determine the cost of track deterioration for different vehicle types regarding deterioration of track geometric quality (both vertical and lateral), component fatigue, and rolling contact fatigue as well as abrasive wear of rails. The set of equations in the model is built into an Excel® environment software called DeCAyS – Deterioration Cost Associated with the Railway Superstructure. The model uses high-frequency wheel loads and wear number as main input for each vehicle type. It is proposed that track force measurements according to the UIC code 518, together with complementary data and simulations, should be used as sources for input. The high-frequency part of the wheel load is accounted for by the unsprung mass of the vehicle. It is also possible to enter measured data on high-frequency forces directly into the software.

By assuming a traffic volume and the total cost per deteriorating mechanism, the track deterioration was determined for different vehicle types. The outcome is that there are very large differences between vehicles and their ability to cause damage to the track structure.

An extensive series of simulations in the dynamic multibody simulation software GENSYS® have given output results on (quasi-static lateral forces, track shift forces and) approximated friction energy loss (the so-called wear number) for two different axle loads and a number of combinations of axle distance, wheel-rail friction and stiffness in wheelset guidance on 4-axle bogie vehicles. These results are examples of a set of data used as input to the deterioration model in particular regarding the friction energy loss and the associated rail wear.