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The focus of this research is to develop a systematic method for ascertaining the level of service (LOS) of gravel roads in the US. To date, such a method does not exist in the highway capacity manual (HCM). In this research, a methodology comprising eight criteria that affect gravel road traffic operations is developed. For each criterion, a rating is assigned. It is either "Good", "Fair" or "Poor". The results of each individual criterion rating are combined to develop an overall LOS rating. Furthermore, a non-parametric machine learning technique, namely the classification and regression tree (CART) modeling structure, is employed to quantify the contribution of each criterion to the overall gravel roads' LOS. As a case study, the developed methodology is implemented to assess traffic operations of gravel roads in Laramie County, Wyoming. The studied gravel road network is compiled and managed in a Geographic information system (GIS) shapefile prepared for the purpose of this research. That is to provide decision-makers in local agencies a computerized tool to efficiently track the performance of their gravel road network. Roughly 63.5% of the gravel road segments are operating at an LOS "Fair", while 19% are operating at an LOS "Poor" and unexpectedly 17.5% are operating at an LOS "Good". All gravel roads assessed are low-volume roads with 400 vpd or less. The developed methodology is intended to benefit traffic engineers, decision-makers, and any other stakeholders. The gravel road LOS methodology was developed and applied to Wyoming's conditions. Minor adjustments might be needed for implementation in other jurisdictions. [ABSTRACT FROM AUTHOR]

Mechanistic-empirical pavement design guide (MEPDG) or Pavement ME Design requires traffic inputs in three levels based on the availability of data and the importance of the project. The availability of site-specific (Level 1) traffic data is generally limited due to expensive cost and the accuracy of Level 3 average is unsatisfactory, and therefore the intermedium level (Level 2) traffic data need to be developed. Using multiple years of weigh-in-motion (WIM) and vehicle classification data from Oklahoma, this paper starts with a comprehensive check of the traffic data quality, and generates site-specific traffic inputs that are required in Pavement ME Design. Cluster analysis is then applied to develop homogeneous groups for each traffic input. Subsequently, decision tree model and multinomial regression model are developed for the selection of appropriate traffic clusters under given site design conditions. In addition, a case study is included to evaluate the variations of pavement performance at various levels of traffic inputs. [ABSTRACT FROM AUTHOR]

Pavement resurfacing is a maintenance activity that is undertaken to enhance the service life of pavement. This pavement resurfacing activity involves laying a new layer of asphalt concrete over existing pavement after certain time. Due to engineering factors, economic variables and uncertainty in forecasting, the pavement resurfacing decision process is a complicated activity. Various optimization approaches currently used are simplified models for finding optimal frequency and resurfacing intensity within pavement maintenance framework. In this research, artificial bee colony algorithm is proposed to solve this pavement resurfacing optimization problem. This algorithm mimics the collective behaviour of bees while searching for nectar. In this approach, various scenarios are generated, optimality of each case is evaluated, and the information thus generated is used in subsequent evaluation until global optimality is reached. The effectiveness of proposed method is demonstrated through a numerical example. The solution obtained is similar to the exact solution reported in literature. The results indicate optimal resurfacing values can be obtained with little computational effort with proposed approach. The main advantage of proposed algorithm is removal of specification of trigger values for maintenance decision. [ABSTRACT FROM AUTHOR]

The mechanical performance of epoxy asphalt concrete has been well reported in existing studies. This study investigated the surface characteristics of asphalt concrete, including the permeability, friction coefficient, moisture damage resistance and surface texture. The permeability test, dynamic friction test, Cantabro test, Hamburg test and laser texture scanning test were carried out for such investigations. Test results show that the permeability of the epoxy asphalt concrete was very low, which is desirable for protecting the steel deck. The friction coefficient can satisfy the requirement for steel deck bridge according to the Pendulum Number. However, it was found that the skid resistance could be a concern when the vehicle speed is higher than a certain level according to the dynamic friction test. The results suggested to control the traffic speed when epoxy asphalt concrete is applied as steel bridge pavement. In terms of the raveling and stripping, it was found that the epoxy asphalt mixture has an excellent anti-stripping performance based on the Cantabro test and Hamburg wheel tracking test results. The yield point was not reached after 20,000 loading cycles at 60 °C in the immersed Hamburg wheel tracking test. The mean profile depth of the epoxy asphalt concrete is 0.305 mm, much lower than conventional asphalt concrete indicating a very fine surface texture. [ABSTRACT FROM AUTHOR]

The objective of this research is to investigate the pavement response of road-bridge transition section without slab under impact load caused by vehicle bumping. The three-dimensional (3D) finite element models (FEM) of road-bridge transition section without slab were developed to simulate the response under impact load. The influence of different parameters (damping ratio, step height, vehicle speed as well as axle load) on the pavement response was investigated. Results indicated that an obvious increase of pavement response was observed with the step height and axle load rising. On the contrary, the rise of vehicle speed and damping ratio led to the decrease of pavement response. In addition, the pavement under impact load exhibited larger response as compared to under static load. Therefore, the phenomenon that static load was considered only in the traditional pavement structure is defective. Finally, the correction coefficients of design index for highway asphalt pavement were proposed to consider the influence of impact load. [ABSTRACT FROM AUTHOR]

In China, the research on asphalt pavement deterioration was hindered by a lack of comprehensive investigations on field data collection of pavement performance within its service life. The problem of traditional methods that yield inadequate data can be addressed using a combination of the Pavement Mechanistic-Empirical (PME) system and matter-element analysis (MEA). Measured data for the rutting of a road section in the Shaanxi province was employed as the validation data in this study. The input parameter for PME was localized, and a decay model based on the predicted results of PME was established by the MEA method. The results from PME indicate that the predicted results of rutting show a ''lagging" characteristic when compared with the measured data. Some optimization measures are employed to process the predicted results of PME so as to better fit the measured data. The predicted data for rutting resistance can be considered essential data for the MEA method to investigate the decay tendency of the rutting of asphalt pavement in its design life. A case study indicates that the rutting resistance of asphalt pavement will deteriorate from excellent to good, good to medium, medium to inferior, and inferior to bad in 13.8 months, 32.5 months, 43.8 months, and 55.2 months, respectively. The combination of PME and MEA proves to be appropriate to evaluate rutting potential in project level pavements. Follow-up research can be carried out on the developing trend of pavement damage, so as to better determine the maintenance time for a chosen road section. [ABSTRACT FROM AUTHOR]

The recent preparation of the Operation and Maintenance (O&M) Manual for Palestinian municipalities is an important step to guide them towards preparing and implementing their O&M priority-based plans, considering scare resources. During the course of preparation of the Manual, the proposed procedures were applied at ten pilot municipalities. This study aims to explore the outcome of the implementation of the 2014 O&M road maintenance plans at these municipalities. To achieve this, analysis of the outcome of a questionnaire designed to collect relevant information from these municipalities was conducted. The results show that seven of the targeted municipalities used the prioritization criteria proposed in the O&M Manual. Despite that the remaining municipalities had the liberty to slightly change the relative weight of the indicators, sensitivity analysis was conducted and indicated robustness of the indicators. The average percentage of roads' lengths of the actually maintained to the planned was 35%, suggesting that the plans were ambitious and need to be more rational. Most of the allocated funds for road maintenance came from the municipalities own budgets, indicating need to have more financing by the government to ensure the integrity of the municipal road infrastructure assets. The results also indicated that 95% of the maintenance works were executed through external contracts, and that the municipalities need to be supported and equipped to conduct the basic road maintenance works. [ABSTRACT FROM AUTHOR]

The traffic input parameters in the Mechanistic Empirical Pavement Design Guide (MEPDG) are: (a) general traffic inputs, (b) traffic volume adjustment factors, and (c) axle load spectra (ALS). Of these three traffic inputs, the traffic volume adjustment factors specifically monthly adjustment factor (MAF) and the ALS are widely considered to be important and sensitive factors, which can significantly affect design of and prediction of distress in flexible pavements. Therefore, the present study was undertaken to assess the sensitivity of ALS and MAF traffic inputs on rutting distress of a flexible pavement. The traffic data of four years (from 2008 to 2012) were collected from an instrumented test section on I-35 in Oklahoma. Site specific traffic input parameters were developed. It was observed that significant differences exist between the MEPDG default and developed site-specific traffic input values. However, the differences in the yearly ALS and MAF data, developed for these four years, were not found to be as significant when compared to one another. In addition, quarterly field rut data were measured on the test section and compared with the MEPDG predicted rut values using the default and developed traffic input values for different years. It was found that significant differences exist between the measured rut and the MEPDG (AASHTOWare-ME) predicted rut when default values were used. [ABSTRACT FROM AUTHOR]

Instrumentation embedded in pavements is increasingly being used to measure the critical responses and monitor performance of specially-constructed experimental pavement sections or in-service pavements under controlled wheel loading or live traffic. On the other hand, nondestructive tests (NDT), such as falling weight deflectometer (FWD) testing, are routinely performed to evaluate pavement layer structural properties based on deflections measured on the surface of the pavements. In cases where measurements from the pavement surface only are not sufficient to infer pavement layer modulus values, e.g. rolling wheel deflectometer (RWD) tests typically with only one deflection measurement or complex geometries, a procedure that combines measurements from the embedded instruments and surface deflections would provide an alternative to the traditional backcalculation of pavement layer moduli.This study presents an inverse analysis procedure integrating finite element (FE) models and a population-based optimization technique, Covariance Matrix Adaptation Evolution Strategy (CMA-ES), to determine the pavement layer structural properties. Tests using a lightweight deflectometer (LWD) were conducted on instrumented three-layer scaled flexible pavement test sections. The time histories of the LWD load, surface deflection underneath the LWD load, subgrade deflection and vertical stress were recorded and used in the inverse analysis. While the common practice in backcalculating pavement layer properties still assumes a static FWD load and makes use of only peak values of the load and deflections, dynamic analysis was conducted to simulate the impulse LWD load. Results of the inverse analysis show that consistent pavement layer properties can be obtained based on the LWD surface deflection data and measurements of the embedded instrumentation. [ABSTRACT FROM AUTHOR]

Since the 1990s the Leutner shear test has become the most important device for testing the interlayer shear bond of asphalt pavements. The test device was originally designed by R. Leutner in the late 1970s, but since different countries and laboratories have made modifications or have built their own equipment. Besides others the gap width between the shearing rings has been a matter of modification. Recently this question also appeared in the process of European standardization. This paper shows the results of a laboratory study in which the gap distance was varied between 0 and 5mm. It was found that the influence of the gap width depends on the asphalt concrete type of the two layers (mixture type, max. aggregate size, and binder content). In most cases the gap width is negligible, in some cases maximum shear force and stiffness value decreases with increasing gap width. In addition to the shear values at the interface, shear tests were conducted in the material itself. Therefore, the difference between in-layer and interlayer shear properties and behavior is also discussed in more detail. [ABSTRACT FROM AUTHOR]

Utilization of local and alternative materials (such as steel slag) is one of the main aims of the road building. This concerns both developed and developing countries. One can obviously notice changes and the rise of requirements for road pavements and materials applied. This occurrence observed lasting recent years is mainly the result of the growth of the intensity of road transportation. It is an important task to meet the more stringent requirements without excessively increasing the costs. Problems resulted from the limited accessibility of mineral aggregates appeared with the considerable growth of financial expenditures on road construction as well as logistics and transportation problems in delivery of aggregate from quarries located on the south of Poland to northern and eastern regions. This study is devoted to the applicability of using limestone aggregates, available in central and northern Poland, in the asphalt mixtures. Laboratory tests showed that limestone aggregate may be successfully used in High Modulus Asphalt Concrete for base and binder courses of road pavements. This result is also confirmed by full scale testing using a Heavy Vehicle Simulator. [ABSTRACT FROM AUTHOR]

The scope of this study is to evaluate the mechanical performance of the polymer modified mastic asphalt with 4% montan wax (Asphaltan A) additive. The impact of wax modification on binder, binder/filler mixtures, and mastic asphalt was investigated in the laboratory. Wax modified binder properties were determined using dynamic mechanical analysis (DMA), Fourier transform infrared (FTIR) spectroscopy and conventional tests (softening point, penetration, elastic recovery, breaking point, viscosity, and storage stability). The bending beam rheometer (BBR) was used for determining low temperature creep compliance and the tensile stress restrained specimen test (TSRST) for determining low temperature fracture. The fatigue cracking behavior of mastic asphalt was investigated using Superpave Indirect Tensile Test (IDT). Based on hot mix asphalt (HMA) Fracture Mechanics the influence of wax on the asphalt mixture resistance to fatigue and brittle cracking has been evaluated. The addition of wax to the polymer modified binder resulted in a viscosity reduction at higher temperatures, indicating a possible lower production and laying temperature as compared to asphalt without wax additive. DMA and BBR results showed some increase in stiffness and a more elastic response of the wax modified binder at medium and low temperatures. The TSRST fracture temperature was higher for the mastic asphalt containing wax, indicating a certain negative impact of wax modification. [ABSTRACT FROM AUTHOR]

The use of recycled asphalt pavement (RAP) in hot-mix asphalt leads to significant environmental and economical benefits. The major benefits are realized through reduced demand for new or virgin aggregates and asphalt binders. A limited amount of research has been performed to investigate the effects of RAP on the low temperature fracture characteristics of asphalt mixtures. However, this is an important subject, since the inclusion of RAP in Hot-Mix Asphalt (HMA) has the potential to increase mixture stiffness and brittleness unless properly compensated for. Most design procedures for mixtures consisting of RAP recommend an asphalt binder grade adjustment to compensate for the aged binder through the use of a softer virgin binder. This study evaluates the validity of this grade adjustment procedure in the context of four RAP materials using mixture fracture testing. The RAP materials used in this study were chosen from a larger database of materials to represent a wide variety of binder aging levels. Various fracture tests for asphalt concrete were identified through literature review. The disk-shaped compact tension (DC(T)) test, as standardized in ASTM D7313-07b, was used in this study to characterize mixture fracture energy. DC(T) fracture tests were conducted on various asphalt mixtures, namely: a control mixture with no RAP, manufactured with PG 64-22 asphalt binder; four mixtures containing 30% RAP from different sources, with an adjusted virgin binder grade of PG 58-28, and; a reference mixture containing no RAP, manufactured using PG 58-28 binder. The test results indicate significant reduction in the fracture energy of asphalt mixtures with 30% RAP and no virgin binder grade compensation. The reduction in fracture energy was surprisingly consistent between the four RAP sources irrespective of the significantly different RAP binder stiffnesses that were determined to be present in these mixtures through binder recovery and testing. However, when the RAP mixtures were produced using a softer virgin binder (PG 58-28), the measured fracture energy was higher than the control mixture. The study provides some assurance that adequate cracking resistance can be maintained in mixtures containing 30% RAP when designed properly, and demonstrates how fracture testing with ASTM D7313-07b can be used in the design and control of RAP mixtures, particularly where cracking is of concern. [ABSTRACT FROM AUTHOR]

The Netherlands is a densely populated country. As a result environmental issues related to road traffic are taken very serious. This paper discusses the mechanistic design of porous asphalt surface mixtures, PA. The environmental advantages of PA are that it dramatically reduces traffic noise. A disadvantage of PA is that the presence of pores reduces the strength of the mixture which is reflected in the materials vulnerability to ravelling. And, to make matters worse, the open structure makes the material vulnerable to aging which further enhances the ravelling vulnerability. Ravelling has a negative effect on noise emission, implying that the main advantage of PA is gradually lost as the development of ravelling damage progresses throughout the service life of PA. Furthermore ravelling of PA is the main reason for PA maintenance. In this paper a mechanistic mixture design approach for PA surfacings and open graded thin surfacings is discussed. The procedure is based on meso scale material mechanics in which the in-mixture response to wheel loadings is simulated and used for further durability determination. The development of the theory summarised and the paper comes to a conclusion by validation of the procedure on the basis of full-scale ravelling tests. It is concluded that the mechanistic design of silent porous surfacing layers is feasible today and that this may well contribute to the introduction of durable and silent road surfacings on a wider scale. [ABSTRACT FROM AUTHOR]

Solid waste management is the thrust area. Of this various waste materials, plastic waste, and municipal solid waste are of great concern. Use of disposed plastics waste is the need of the hour. On the other side, the road traffic is increasing. The traffic intensity is increasing. The load bearing capacities of the road are to be increased. The studies on the improvement of road strength using polymer modified bitumen (PMB) for flexible pavement are being carried out by different schools. Virgin and recycled polymers are being used for these studies. But when higher percentage of plastics waste was used, the polymer got separated from the blend. Hence a new innovative technique was developed the author and the heated stone aggregate was first coated with plastics generated from wastes like carry bags, films, foams, and multi layers and the plastics waste coated aggregate (PCA) was used as the raw material for flexible pavement. PCA is then mixed with 60/70 or 80/100 bitumen and the mix is used for road construction. PCA + Bitumen mix showed better binding property. It had less wetting property. Its voids were much less. The sample showed higher Marshall Stability value. By this process a road of 1km length and 3.75m width of single lane can consumes 10,00,000 carry bags and the road strength is increased by 100% and there is no pothole formation. The roads laid using PCA + Bitumen mixes are performing well. Performance studies were carried out for plastic road of different ages and reported in this paper. [ABSTRACT FROM AUTHOR]

The article offers information on the U.S.-China Workshop on Research and Education Collaboration in Transportation Infrastructure held in Washington, D.C. on January 23, 2011. The workshop, themed "Asphalt Pavement Technology in China," was organized jointly by the International Association of Chinese Infrastructure Professionals and the Research Institute of Highway of China. Topics discussed focused on the area of pavement and traffic engineering.