Background: Various preventive maintenance treatments are employed by highway agencies to restore pavement condition and retard future deterioration. For specific climate conditions and traffic levels, the performance of the restored pavement will depend not only on the type of maintenance treatment, but also on the existing pavement condition when these treatments are applied. However, these relationships are not well documented. Without this information, the determination of the optimal timing for applying a specific preventive maintenance treatment is a difficult task.

Research is needed to develop a a guide for determining optimal timing of pavement preventive maintenance treatments. However, recognizing the lack of sufficient data to develop such a guide, a methodology for determining the optimal timing for the application of pavement preventive maintenance treatments needs to developed to serve as a basis for developing such a guide when needed data becomes available.

Objective: The objective of this research is to develop a methodology for determining the optimal timing for the application of preventive maintenance treatments to flexible and rigid pavements. The research will also create a user-friendly tool to facilitate use and implementation of this methodology for the variety of pavement maintenance situations encountered by highway agencies; demonstrate the applicability of the methodology and the suitability of the implementation tool using data from a limited number of projects or other means; and develop a plan, for use by highway agencies, to collect the data needed to support the proposed methodology. For the purpose of this research, preventive maintenance is defined as a planned strategy of cost-effective treatments to an existing roadway system that preserves the system, retards future deterioration, and maintains and improves the functional condition of the system (without substantially increasing structural capacity). This research is not concerned with treatments of appurtenances.

Tasks: Accomplishing this objective will require at least the following tasks.

Phase I: (1) Collect and review information on the timing, selection, and performance of preventive maintenance treatments of flexible and rigid pavements. This information may be obtained from published and unpublished reports, contacts with public- and private-sector agencies, industry organizations, and other domestic and foreign sources. For each identified preventive maintenance treatment, summarize the information assembled. (2) Based on the results of Task 1, identify appropriate preventive maintenance treatments for ranges of climatic conditions, traffic levels, and pre-treatment pavement conditions for consideration in this research. (3) Recommend and describe a methodology for identifying the optimal timing for application of preventive maintenance treatments, and prepare a plan for further refining it. The methodology shall consider the cost-effectiveness and performance of each maintenance treatment. (4) Prepare and submit an interim report that documents the research performed in Tasks 1, 2, and 3, and propose a revised work plan for Phase II. Following review of the interim report by the NCHRP, the research team will be required to make a presentation to the project panel. Work on Phase II of the project will not begin until the interim report is approved and until the Phase II work plan is authorized by the NCHRP.

Phase II: (5) Refine and document the methodology developed in Phase I for determining optimal timing for preventive maintenance treatments. (6) Create a user-friendly tool to facilitate use and implementation of the methodology for the variety of pavement maintenance situations encountered by highway agencies. The software shall be capable of handling data trends and includes a section on user costs. (7) Demonstrate the applicability of the methodology and the suitability of the implementation tool using data from a limited number of projects or other means. (8) Develop a plan, for use by highway agencies, to collect the data needed to support the proposed methodology. (9) Submit a final report that documents the entire research effort.

Status: The research has been completed and a final report has been received and distributed to NCHRP sponsors (i.e., state departments of transportation). The report is published as NCHRP Report 523. The methodology for determining optimal timing for preventive maintenance treatments--presented in the form of Visual Basic-driven Excel spreadsheet and designated OPTime--and related user's guide are available on the NCHRP website as supplemental material.

Product Availability:  NCHRP Report 523.