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Publication Number:  FHWA-HRT-13-038    Date:  November 2013
Publication Number: FHWA-HRT-13-038
Date: November 2013

 

Reformulated Pavement Remaining Service Life Framework

Chapter 8. Strategy Selection

INTRODUCTION

In order to select the most appropriate corrective pavement construction strategies, many considerations must be taken into account, beginning with the pavement condition subject to other constraints such as budget, bridge height clearance, guard rail adjustment, buried utilities, etc. At the network level, the objective is to characterize the current and future condition state of pavements included in the system that require corrective treatments. At the project level, the objective is to provide detailed decisions on what corrective construction treatments are needed for each project identified from the network-level analysis.

The current challenge to SHAs is to create a rational basis to move from a worst-first to a best-first allocation of available agency repair resources. Research has shown that application of corrective construction treatments at the proper time can extend the time until more costly treatments are required. These types of treatments are applied before too much damage has accumulated; hence, the pavements are not in the worst condition. To find these favorable pavement conditions at the optimum time requires knowledge of how a pavement will respond to the prescribed treatment plan based on its current condition.

There are also situations within a pavement network where pavements in a worse condition state should be allowed to continue to deteriorate. This decision is appropriate for pavements that have accumulated significant structural damage but are still smooth and provide adequate service otherwise.

NETWORK ANALYSIS

At the network level, the objective is to characterize the current condition state of pavements included in the system that require corrective treatments. Since network-level data tend to be more aggregated and less specific, the performance models used to predict performance can have greater variability. Likewise, strategy selection may be broken down into broad categories using a standard set of cost assumptions based on the treatment type.

Recommended practice at the network level is to use LCC concepts as a means to optimize the selection of construction projects in the next cycle and forecast future construction needs. These concepts are based on considering multiple streams of future construction activities driven by the prediction of future changes in pavements. Optimization is an objective function whose performance is based on measured field conditions and main factors that are sensitive to future construction activities. In a simple system, optimization is achieved when the best performance of the system is obtained using the available budget.

The pavement performance concept considers the time-history of a chosen functional aspect of a pavement. Serviceability has been used in the past where scale is used-the lower the number, the worse the pavement condition. Using this type of scale, the objective function could maximize the area under of the serviceability-time history curve. If a numeric such as IRI is used, then optimization of the objective function should focus on minimizing the area under the IRI-time curve since IRI uses an increasing scale where higher numbers indicate pavements in worse condition.

The limitations of construction strategy selection at the network level are determined by the sophistication of the system processes. It is not uncommon that the construction cost assumptions used in the network optimization planning process do not match those developed from project-level design considerations. Continual improvements are being made to field data collection techniques, construction cost models, and new performance prediction curves. Modern automated field data collection systems are capable of providing greater amounts of data with increased specificity that approaches what used to be considered project-level data. This increased data availability requires updates to the construction triggers, threshold limits, and performance curves used by SHAs in their network-level strategy selection process.

Strategy selection at the network level are primarily determined by computer algorithms capable of accounting for all of the factors included in the simulation of future pavement condition states and performing the millions of calculations for impact of alternative strategy scenarios needed for optimization of available budgets.

PROJECT ANALYSIS

Project-level analysis is based on indepth considerations of pavement conditions after a network-level planning process has identified a pavement segment in need of corrective construction. The first level consideration determines the construction need as well as maintenance, restoration, resurfacing, rehabilitation, or reconstruction needs. The most significant difference between network and project-level strategy selection is that project-level decisions are based on human interpretations of available data and information as opposed to reliance on automated computer algorithms.

At the project level, LCCA can be supplemented with cost engineering considerations specific to each project site. Cost engineering concepts require more intensive inputs on the resulting affects of alternative design considerations than those generally available at the network level. This level of consideration is based on a cost-benefit analysis of alternative construction treatments centered on a greater range of treatment options.

Project construction programming is the last chance to integrate other related infrastructure construction needs into managing pavement assets. In urban areas, the timing of new utility cuts into a pavement structure should be coordinated with repaving events. Having a utility company perform changes to a pavement structure less than 3 years since the last construction event is often an indication of lack of coordination between publically funded city/regional departments. Studies on the impact of the repair of utility cuts in pavements have shown that they return the pavement to less than as new condition and can advance deterioration of the surrounding pavement structure.(10)

 

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