First define a finite number of condition states e.g. for an index with 5 as the best possible value, Condition State 1 is 4-5, Condition State 2 is 3-3.9 etc. Place all of your points from the pavement management database into their respective condition states. Then find the sum of the miles (or km) in each condition state. Then you need to find the number of miles transitioning from one state to another. 

Pij = Total miles from State i to State j / Total miles in State i

Pij should be greater than or equal to 0 for all i and j

Summation of Pij in each row of the matrix should be 1

Hi professor Bazlamit ,

You could use a multiattribute objective value function and after that some stochastic model.

Pavlov

Thanks Professor Pavlov. I think both suggestions are valuable. However, professor Reza seems to relate more to the situation. I appreciate the input from both of you. I do recommend that others take a look at the Multi-attribute objective value function . I had used it in decision analysis of alternative solutions

I agree with all above which share the same principles of identifying an optimum condition and then a decision method that represents or simulate the deterioration of the selected pavement structure which also dependent how fast is expected to deteorieteroriate taking into consideration traffic loading frequency and weather