2. The time stream of costs over the life of a roadway depends upon the intervals at which rehabilitation is carried out. If the rehabilitation strategy and the traffic are known, the time stream of costs can be estimated (15 points). Using a life cycle model which predicts the economic life of highway pavement on the basis of the effects of traffic and other factors, an optimal schedule for rehabilitation can be developed. For example, a time stream of costs and resurfacing projects for one pavement section is shown in the figure below. As described in the previous example, the routine maintenance costs increase as the pavement ages, but decline after each new resurfacing. As the pavement continues to age, resurfacing becomes more frequent until the roadway is completely reconstructed at the end of 35 years. $743k Reconstruction 744 742 740 154 $152k Resurfacing $152k Resurfacing 152 150 148 8 Expenditure in Thousands of 1967 Dollars $(4+0.15x)k x is the number of years from resurfacing Routine Maintenance Routine Maintenance 0 5 10 15 20 25 30 35 Years Time Stream of Costs over the Life of a Highway Pavement (costs are plotted to-scale) Evaluate an alternative maintenance plan by assuming routine maintenances only take place every other year but cost about twice the yearly maintenance schedule - i.e., the bi- yearly maintenance cost is estimated by $(9+0.3x)k, where x is the number of years from last resurfacing. Assuming inflation rate of 1.8%. 00 (0 NO 6 4 2 2. The time stream of costs over the life of a roadway depends upon the intervals at which rehabilitation is carried out. If the rehabilitation strategy and the traffic are known, the time stream of costs can be estimated (15 points). Using a life cycle model which predicts the economic life of highway pavement on the basis of the effects of traffic and other factors, an optimal schedule for rehabilitation can be developed. For example, a time stream of costs and resurfacing projects for one pavement section is shown in the figure below. As described in the previous example, the routine maintenance costs increase as the pavement ages, but decline after each new resurfacing. As the pavement continues to age, resurfacing becomes more frequent until the roadway is completely reconstructed at the end of 35 years. $743k Reconstruction 744 742 740 154 $152k Resurfacing $152k Resurfacing 152 150 148 8 Expenditure in Thousands of 1967 Dollars $(4+0.15x)k x is the number of years from resurfacing Routine Maintenance Routine Maintenance 0 5 10 15 20 25 30 35 Years Time Stream of Costs over the Life of a Highway Pavement (costs are plotted to-scale) Evaluate an alternative maintenance plan by assuming routine maintenances only take place every other year but cost about twice the yearly maintenance schedule - i.e., the bi- yearly maintenance cost is estimated by $(9+0.3x)k, where x is the number of years from last resurfacing. Assuming inflation rate of 1.8%. 00 (0 NO 6 4 2