Urban Road Repair Structural Design of Urban Roads

Municipal engineers are faced with the difficult task of managing the urban roadway network. Maintaining this significantly large and expensive infrastructure requires effective planning and design. However, the majority of currently available design tools were developed originally for analyzing highway pavements. Little attention has been given in the past to urban road related issues. The environment under which urban roads operate is uniquely different from highways. Traffic in urban roads is slower and involves braking and turning maneuvers, which introduces critical loading conditions to a pavement surface. Heavy urban buses is another traffic element contributing to the critical loading conditions in urban roads specially at intersections, near loading stations and along Transitways (dedicated bus lanes). Urban road users and businesses are very sensitive to traffic disruptions specially those associated with maintenance operations. The presence of utility pipes and the need to reach them by cutting the road for maintenance purposes or for adding new services, also affect the performance of urban roads. All of these unique characteristics suggest the need for urban pavement analysis beyond that developed for highways. Review conducted by a multi-disciplinary research team assembled at the National Research Council of Canada, revealed a number of deficiencies in the adopted practices. However, the most significant weakness relates to the theoretical construct that supported earlier developed systems for pavement analysis. Inadequacies of these systems made their use in carrying out road engineering tasks such as material selection, structural design and performance prediction unreliable and less effective. This paper addresses these inadequacies while focusing on critical elements of pavement analysis such as modeling of pavement materials, the road pavement structure and traffic loading. The paper also discusses a new approach to pavement analysis, which benefits from recent developments in material science and engineering mechanics, to demonstrate its effectiveness in addressing urban road engineering requirements. The success of the proposed new approach lies in its ability to accurately determine the state of stress associated with realistic traffic loading conditions, an essential element in producing the information necessary for making correct design decisions. Of particular importance is the ability of the new approach to account for pavement inservice condition while predicting performance, a factor completely ignored in current pavement analysis exercises aimed at selecting the appropriate rehabilitation measure and proceed with its design.