Statistical inference for Markov deterioration models of bridge conditions in the Netherlands

The focus of this paper is on the statistical estimation of parameters in various types of continuous-time Markov processes using bridge condition data in the Netherlands. The parameters in these processes are transition intensities between discrete condition states. These intensities may depend on the current state and on the age of the structure. The likelihood function for the observed transitions is derived and an outline of the steps to determine the parameters which maximize the likelihood function is given. The results of the fitting procedure are presented in the form of the expected bridge condition over time and the random time to the final state. For each type of Markov process, the quality of fit is compared to that of the other types. The influence of the inspector on the condition process is also discussed.