Development of the Thruway Authority’s multi-year program is based on the following goals/guidelines:
Maintain pavement and bridges in good condition; Maintain safety/correct safety critical elements; Minimize costs to the extent possible;
Implement projects that significantly enhance customer service/operations or efficiency;
Maximize or exhaust the safe remaining life of every bridge;
Recognize differing functions of mainline, overhead, and ramp bridges and prioritize work accordingly; and
Address prioritized reconstruction needs and capacity improvements. Currently lifecycle costs are considered during scoping. In the future, whole life management of assets is expected to be more tightly integrated into decision making and operations.
5.0 Whole Life Management
This chapter introduces the principles of life cycle management and the resulting Whole life management process adopted by NYSDOT. Whole life management considers the most economical approach to manage inventories of assets by applying cost effective investment strategies. Whole life management applies the principles of life cycle cost analysis to program management practices. Just as traditional life cycle costing leads to the selection of the most cost effective alternative for a project, whole life management leads to the selection of the most cost effective strategies for managing multiyear, multiasset investment programs.
5.1 LIFECYCLE
COSTCONSIDERATIONS
All physical assets deteriorate with age and use. As assets deteriorate there are appropriate treatments which can be applied to slow or repair that deterioration. In general, treatments can be categorized by their impact and cost:
Preventive maintenance treatments typically arrest deterioration without significantly improving condition or provide a modest improvement in condition. These treatments are only applicable to assets that are still in relatively good condition. Examples of preventive maintenance treatments include crack sealing, thin pavement overlays, and waterproofing concrete.
Corrective maintenance treatments generally involve repairs to specific elements or aspects of an asset. These treatments are used for assets which are in fair to good condition, but in need of specific repairs. Examples of corrective repairs include concrete repairs on bridges and bump grinding.
Rehabilitation is required for assets which still have a potential for significant remaining service but have a substantial number of components in need of repair, or major components in need of substantial repair. Examples of rehabilitation treatments include bridge deck replacement and multi-course pavement overlays.
Replacement/reconstruction is required when an asset has reached the end of its service life and can no longer be extended though repair or rehabilitation.
type is the proper treatment for the distress in the asset is called the “window of opportunity.”
Figure 5.1 illustrates the window of opportunity concept for pavements. As a pavement deteriorates there is a period of time, a window of opportunity, to perform a lower cost treatment before the distress becomes too severe and a more expensive treatment is required to properly repair the pavement. This concept is true for each treatment window the pavement passes through, as untreated distress continues to advance.
Windows of opportunity are treatment specific. For example, the window of opportunity for a preventive maintenance overlay on pavement is approximately 3 years, while the window of opportunity for a more extensive treatment like mill and inlay is between 5 and 10 years. This does not mean the preventive maintenance overlay will only last for three years. It is simply the time period in which a preventive maintenance overlay is the appropriate treatment for the pavement. If applied within the window of opportunity the preventive maintenance overlay should last 7 years or more.
Figure 5.1 Pavement Performance Windows of Opportunity
9The dollar amounts shown in Figure 5.1 represent the ratio of typical costs between treatments which are appropriate in each window of opportunity. In general, the cost of treatment increases exponentially between categories. For example, the typical cost of a thin overlay on a good pavement is approximately $75,000 per lane-mile. The cost to mill and place two layers of asphalt on the same pavement when it reaches fair condition is typically $250,000 to $400,00 per lane-mile. The typical cost to rehabilitate that pavement if it reaches poor condition is $1 to $5 million per lane-mile. Because major work is necessary to recover the condition of poor assets, cost of preservation treatments, even applied multiple times over the assets life, are several times less expensive than postponing that work and replacing the asset prematurely.
This same concept applies to bridges, but is more complex as each component of the bridge deteriorates along its own curve and each has independent windows of opportunity. NYSDOT’s whole life approach to managing bridges recognizes the causality of robust cyclical and preventive maintenance programs and prolonging the service life as well as slowing the rate of deterioration of structures.
Conceptually, the effects of a systematic maintenance program can be graphically represented as shown in Figure 5.2. The red line shows the straight-line deterioration of a theoretical bridge which receives no maintenance. The blue line demonstrates the additional service life possible through timely application of maintenance. The shadowed segments represent the four windows of opportunity for bridges, while the colored bars show how many of NYSDOTs bridges currently are in each window. Finally the hatched area to the right shows the relative cost difference between typical treatments necessary to address conditions within each window.
Figure 5.2
10Figure 5.2 was developed based on NYSDOT bridge inventory and inspection data