Comparison of Pavement Performance Models for Urban Road Management System

The key factors for effective pavement management system (PMS) are timely preservation and rehabilitation activities, which provide benefit in terms of drivers’ safety, comfort, budget and impact on the environment. In order to reasonably plan the preservation and rehabilitation activities, the pavement performance models are used. The pavement performance models are usually based on damage and distress observations of rural roads, and can be applied to forecast the performance of urban roads. However, the adjustment of the parameters related to traffic volume, speed and load, climate conditions, and maintenance has to be made before adding them to PMS for urban roads. The main objective of this study is to identify the performance indicators and to suggest pavement condition establishment methodology of urban roads in Vilnius. To achieve the objective, the distresses (rut depth and cracks), bearing capacity, and international roughness index (IRI) were measured for fifteen urban roads in service within a two-year period. The distresses, rut depth and IRI were collected with the Road Surface Tester (RST) and bearing capacity of pavement structures were measured with a Falling Weight Deflectometer (FWD). The measured distresses were compared to the threshold values identified in the research. According to the measured data, the combined pavement condition indices using two methodologies were determined, as well as a global condition index for each road. The analysed roads were prioritized for maintenance and rehabilitation in respect to these criteria. Based on the research findings, the recommendations for further pavement condition monitoring and pavement performance model implementation to PMS were highlighted.

Deterioration Pattern of Flexible Pavement with the Help of Falling Weight Deflectometer

Maintenance and repair of the highway network system are major expenses in the state budget. For this reason, various concerned organizations are pointing out the need for developing an intelligent and efficient pavement performance model that can prioritize pavement maintenance and rehabilitation works. Such models can forecast the remaining pavement service life and pavement rehabilitation needs, and can help in the formulation of pavement maintenance and strengthening programmes which will reduce the road agency and road user costs. The flexible pavement performance or deterioration models involve the complex interaction between vehicles, environment, structure and surface of the pavement. Performance models relating to the pavement distress conditions like, cracking, ravelling, potholing, and roughness are analysed and developed by various researchers. Understanding the deterioration pattern of the flexible pavement is very important in order to take the decision for strengthening the pavement. The remaining life of the pavement depends on various factors such as Traffic, Environment and climatic conditions hence keeping in mind these factors. the thesis presents the pattern of the deterioration of remaining life of pavement. The thesis emphasis on determining the remaining life of pavement by conducting the FWD test. The FWD test is conducted on the same pavement for three time at regular interval to verify the remaining life of the flexible pavement.

DEVELOPMENT OF PAVEMENT PERFORMANCE MODEL FOR PROPER REHABILITATION AND MAINTENANCE USING FIRST ORDER MARKOV CHAIN

The development of pavement performance model is an important step in prediction the future condition of pavement section and accordingly identifying the right road rehabilitation and maintenance in the right time for the right section. The first order Markov chain probabilistic model is used to predict the degradation of flexible pavement in Palestine. A pilot study is conducted on part of the road network in Nablus City. Visual road condition assessment is performed, and the Pavement Condition Index (PCI) is used in rating pavement sections by dividing the roads each 100 m length. The prediction of the pavement condition rating for each section in the first five to ten years of section age will enhance the applying of preventive maintenance strategy and consequently urges the Local Governmental Units to use the limited allocated budgets specified for pavement maintenance in a cost-effective manner by applying maintenance actions such as crack sealing, surface patching, micro-surfacing, milling and overlay, etc.

Economic Effects of Lifting the Spring Load Restriction Policy in Minnesota

Spring load restrictions (SLR) regulate the weight per axle carried by heavy trucks during the spring thaw period. This policy aims to reduce pavement damage caused by heavy vehicles and extend the useful life of roads, but it also imposes costs on the trucking industry. A cost/benefit study, based on the results of surveys of industry costs, a pavement performance model, and a freight demand model, concludes that the benefits of lifting the existing SLR policy outweigh the additional costs. The cost of additional damage should be recovered from those who benefit from the change in policy.

Effects of ‘road friendly’ suspensions on long-term flexible pavement performance

This paper examines the effects of ‘road friendly’ heavy goods vehicle suspensions on long-term flexible pavement performance. A deterministic ‘whole-life pavement performance model’ (WLPPM) is used to calculate pavement damage due to realistic traffic and environmental loading. The traffic is modelled first as a fleet of steel-sprung heavy goods vehicles and second as a fleet of ‘road friendly’ air-suspended vehicles. The pavement life predictions are compared for the two cases and with results from a simple road damage analysis based on the ‘fourth power law’. It is concluded that changing to a fleet of ‘road friendly’ vehicles would not significantly affect the life or maintenance costs of thicker asphalt pavements (motorways and trunk roads) where the mode of failure is permanent deformation (rutting). However, the life of thinner pavements (minor roads) that fail by fatigue damage and pot-holing would be increased significantly if the vehicle fleet changed to road friendly suspensions. Predictions from the simplified fourth power law approach tend to significantly overestimate the benefits of road friendly suspensions for major road conditions compared to the WLPPM predictions. It is concluded that the potential economic benefits in England and Wales of converting to air suspensions may be only 30 per cent of those predicted by the authors of the EC ‘road friendly suspensions’ regulations.

Effects of Spatial Repeatability On Long-Term Flexible Pavement Performance

The effects of spatial repeatability of dynamic tyre forces on the long-term performance of three typical British pavement constructions are investigated. Long-term pavement performance is calculated using a ‘whole-life pavement performance Model’ (WLPPM). The WLPPM is capable of predicting deterministic pavement damage due to realistic traffic and environmental loading, throughout the life of the pavement. Particular attention is given to modelling dynamic tyre forces and patterns of loading applied to the pavement by a typical fleet of heavy vehicles. A method is described for simulating vehicle fleets with varying degrees of spatial repeatability using a small number of dynamic tyre force histories. Results indicate that thinner pavements are most sensitive to the level of spatial repeatability exhibited by the vehicle fleet. Pavement damage predictions made without assuming an appropriate level of spatial repeatability can be in error by 20–150 per cent, the higher values being for thinner pavements that fail by fatigue damage.

A Model of Whole-Life Flexible Pavement Performance

A new ‘whole-life’ pavement performance model (WLPPM), which is capable of making deterministic pavement damage predictions due to realistic traffic and environmental loading, has been developed. A vehicle simulation is used to generate dynamic tyre forces that are a function of distance along the road. These dynamic tyre forces are then combined with the appropriate pavement primary response influence functions (stress, strain and displacement) to give primary response histories at regularly spaced points along the pavement. The primary response histories are then transformed into pavement damage (fatigue and permanent deformation) using an appropriate damage model. The result is an increment of damage at each point along the pavement due to a single vehicle pass. The pavement surface profile is then updated to reflect permanent deformation damage and the layer material parameters are changed to reflect fatigue damage. The procedure is then repeated for the next vehicle pass. Particular attention is given to modelling strength variations in the pavement and dynamic tyre forces. The model is used to investigate the relationship between ‘hot spots’ (due to peak dynamic loads), ‘weak spots’ (due to initial pavement stiffness variations) and long-term pavement damage.