Development of performance models and maintenance standards of urban pavements for network management.
Authors:   , Osorio Lird Alelí 
Published: October 2023

Urban pavements in developing countries often provide users with low level of services and result in negative impacts on the population and economy. Two main causes of deferring maintenance actions for urban pavements in developing countries were identified: an institutional organization that limits the optimization of resources assigned to urban pavements because current regulations may not be clear on the responsibilities and faculties of agencies in charge of urban pavement management, and; the lack of effective technical-economic tools that may help agencies in the decision-making process as an updated management system adapted to prevailing urban pavements maintenance requirements. Although the current state-of-the-art and the-practice of PMSs presents great developments in the last decade for interurban pavements, effective tools developed for urban pavement management are still a missing part of current practices. Compared with the management of interurban roads, the management of urban pavements is a comprehensive task given the complexity of urban networks, the coordination with various services and the variable traffic demands. Given this scenario for urban pavement management, there is a need for better understanding urban pavements performance for network management. An overall condition index that combines most relevant distresses affecting urban pavements performance is required for network analysis due to several pavement condition indices available were developed for interurban road networks (highways, express corridor, etc.); moreover, several performance models have been developed for particular distresses, and some of them for pavement condition indexes of interurban pavements. Then, their direct application to urban networks (streets, avenues, etc.) is not representative and their adaptability for these conditions requires previous adjustments and calibration. This research was focused on the network level analysis of urban pavements, towards the development of practical and sustainable technical tools to be further integrated into an Urban Pavement Management System (UPMS). The main objective was to calibrate an Urban Pavement Condition Index (UPCI) and Performance Models, technical components required for an UPMS, based on data collected in urban networks in Chile. UPCI for asphalt and concrete pavement, based on objective measures of surface distresses and evaluations of an expert panel was successfully calibrated and validated with a confidence level of 95%. Multilineal regressions were performed to obtain the UPCI models. Three UPCI models were obtained for asphalt pavements with manual and automated data collection. The distresses resulted significance in asphalt pavement condition are fatigue cracking, transverse and reflection cracking, deteriorated patches, rutting, and potholes for manual data collected. IRI replaces potholes in the condition equation for automated data collected. One UPCI model was achieved with successfully validation for concrete pavements with manual data collection. The distresses representative of concrete pavement condition are longitudinal, transversal and oblique cracking, corner breaks, deteriorated patches, faulting, and deteriorate joints and cracks. Deteriorated patches have an important effect in the UPCI value for all UPCIs calibrated, where utility cuts are frequently observed, resulting in low quality patches and high probabilities of premature deterioration. This conclusion supports the primary hypothesis that special condition evaluation guidelines and indicators are required for urban pavements. Distress evaluation guidelines for asphalt and concrete pavements considering manual and automated surveys were developed and satisfactory validated with a 95% of confidence level through repeatability and reproducibility analysis. This guideline proposes an evaluation methodology for the distresses included in the UPCI. Based on the field evaluation carried out during the research, recommendations about the frequency and sampling for pavement condition evaluation are given for different network hierarchies: primary, every 2 year, the complete network; secondary, every 4 year, the complete network, and; local, every four years samples of homogeneous sections. Performance models were performed based on probabilistic trends of UPCI observed during field evaluations for asphalt and concrete pavements. Five field evaluation campaigns were developed in three regions of Chile during a three-year analysis period for the calibration and validation of performance models. The climates included were dry, Mediterranean and humid. The probabilistic trend over time of data collected was analyzed using Markov chains with Monte Carlo simulation that facilitates the analysis of the deterioration trend with only two points of the curve condition over time, allowing the simulation of pavement performance within the timeframe of the research. Fourteen performance models were calibrated for different combination of three climates, two pavement types and three hierarchy networks, considering a pavement life cycle of 25 years. Twelve of them were successfully validated with a confidence level of 95%. The models of asphalt in humid climate and concrete in dry climate need further analysis for their validation, considering more data collection in these climates. Hierarchies based on grouped functional classification were used: Primary Network (Express and Troncal streets), Secondary Network (Colectors and Services) and Local Network (Local and passages). Additionally, a comparative analysis was performed between the real equivalent axles demanding the sections and the equivalent axles admitted by their structures, in sections of Mediterranean climate. In other climates, the data was not enough to perform this analysis. Five models were obtained for asphalt pavement in mediterranean climate: three for the hierarchies and two for the design analysis. The latest two are recommended to use when information about traffic and structure is available. On the contrary, the models developed based on the hierarchy networks are recommended. Two performance models resulted for asphalt pavements in dry and humid climate: Models for humid climate presents higher deterioration rate than model for dry climate. However, both models present a shorter service life than their design. Likewise asphalts, five models were obtained for concrete pavements in mediterranean climate. Considering the models resulted from the analysis of the design, the deterioration trend does not present big differences within the two conditions analyzed. Therefore, for concrete pavements is recommend the use of the models calibrated based on the hierarchy networks. Two models resulted for concrete pavements in dry and humid climate: Both cases present a long service life; however, on the contrary of what is expected, the dry climate presents a deterioration more accelerated than humid climate. This behavior is probably a consequence of differences in construction standards and maintenance policies, noticed in interviews carried out with agencies of both regions. Finally, suitable P&M&R standards for urban pavement based on the urban pavement condition index and their performance models were developed for asphalt and concrete pavements. Three different standards are proposed for primary, secondary and local networks. The practical tools calibrated in this research can be easily implemented and used by local agencies, and simply adaptable over time and to different scenarios. The results of the study were developed with field data collected in Chilean cities; however, the results may be adapted and adopted in other countries for urban pavement management.