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Permanent deformation is the primary failure mode for the asphalt concrete (AC) pavement in urban environment. It is mainly caused by a combination of heavy traffic load, low vehicle speed and channelised traffic. A rut prediction model would therefore be a valuable tool for planning maintenance scheduling and selecting an appropriate asphalt material. This study uses the PEDRO (Permanent deformation in asphalt concrete layers for roads) model to evaluate the rutting performance of flexible pavements in dedicated bus lanes and intersections in urban areas. For this purpose, three road sections along a bus lane in Malmö, Sweden, were selected. To achieve this, AC cores from the road sections were tested using a Shear Box Tester to characterise the asphalt mixtures. Traffic data such as axle load, tyre configuration, speed, and lateral wander distribution of vehicles, and climate data were measured for the selected sections. Field measurements were carried out to assess the structural conditions of the pavements and to measure transverse profiles. This study introduced a procedure for the evaluation and local calibration of the PEDRO rutting model. The results revealed that the prediction of the transverse profiles are generally in good agreement with the rut measurements. [ABSTRACT FROM AUTHOR]

Road agencies are looking for efficient pavement management tools to maintain adequate service levels and preserve the asset value. The traffic speed deflectometer (TSD) allows to continuously assess the structural condition of the pavement while moving at traffic speeds, thus overcoming the typical drawbacks of traditional non-destructive testing equipment. However, managing the huge amount of data deriving from TSD surveys is challenging, and there is no established method to use those data for identifying the remaining service life (RSL) of the pavement network. This study aimed at developing a new practical and reliable methodology to assess the RSL of motorway pavements at the network level from TSD measurements. The methodology is based on the use of the surface curvature index SCI300 and includes the temperature adjustment, the definition of a representative SCI300 value for each pavement section and the estimation of the residual fatigue resistance (considering bottom-up cracking as the critical distress). The methodology was implemented using the deflection data deriving from a TSD survey carried out on about 400 km of motorway pavement. The obtained RSL predictions can be used to identify the structural ranking of different pavement sections and guide budget forecasting, according to the actual maintenance and rehabilitation priorities. [ABSTRACT FROM AUTHOR]

The response of asphalt material depends on the rate of loading and varies from elastic to plastic. Therefore, the behaviour of flexible pavement would also be different along the entire length of a road because of truck speed changes due to the existence of police checkpoints, bus stations, speed bumps, intersections, horizontal and vertical curves, and climbing lanes. The objective of this study is to investigate the effect of truck speed on the performance of flexible pavement. Thus, analyses were conducted for various truck speeds (1–75 km/hr) on three different pavement structures and three traffic levels using AASHTOWare Pavement ME Design 2.5.5 for the local conditions of Izmir, Turkey. The analysis results of the study manifested that a reduction in traffic speed (75–1 km/hr) on a road resulted in higher pavement distress. According to the results, reducing truck speed from 25 to 1 km/hr resulted in a rapid increase in AC rutting, alligator cracking and top-down cracking by 13.3 mm, 10.6% and 1473.8 m/km, respectively. It is expected that the outcomes of this study would promote the local calibration of the mechanistic-empirical pavement design guide (MEPDG) and pavement design in Turkey and the region. [ABSTRACT FROM AUTHOR]

Wet pavement surface on rainy days poses a challenge for traffic safety as it greatly impacts the safe driving speed and increases the hydroplaning risk. This study proposed a new approach to analyse and mitigate hydroplaning risk on roadways based on spatial-temporal water conditions and hydroplaning speeds. A theoretical analysis was conducted to predict the spatial-temporal water film depth under dynamic rainfall profile, considering the effects of roadway slope and pavement surface texture. The tire-water-pavement interaction model was then used to predict hydroplaning speeds of vehicles driving on different traffic lanes. According to the hydroplaning and traffic flow speeds, the spatial and temporal pattern of roadway hydroplaning risk was analysed. Considering traffic flow speeds, rainfall intensity, roadway geometry, and surface condition, the probability of hydroplaning occurrence at different times of rainfall and separate traffic lanes can be estimated using the proposed approach. Finally, the variable speed limits (VSL) approach was proposed to mitigate hydroplaning risk, which can be determined based on the hydroplaning threshold probability and the design speed limit of the roadway section. [ABSTRACT FROM AUTHOR]

The traditional practice for pavement structural capacity evaluation is mostly dependent on the falling weight deflectometer (FWD) measurements. However, this practice has several challenges due to its stationary nature. Recently, a Rolling Weight Deflectometer (RWD), capable of measuring the pavement deflections at regular traffic speeds, has been introduced into the market. This research aims to develop a finite element (FE) model simulating pavement structural response under the moving RWD loads. This model could be further utilised for accurately estimating pavement layers mechanical characteristics. The model was successfully validated utilising the RAPTOR (a commercially available RWD) data collected on the National Center for Asphalt Technology (NCAT) test track. A good correlation between the simulated and the measured values was found – yielding an average root mean square percentage error (RMSPE) of approximately 2.40% between the RAPTOR and the FE deflections. [ABSTRACT FROM AUTHOR]

The paper presents a comparison of friction coefficients and MPD (Mean Profile Depth) parameters of EAC (Exposed Aggregate Concrete) pavements with a maximum aggregate size of 8, 11 and 14 mm. In order to obtain for all tested EAC pavements the same conditions that simulate the phenomenon of polishing, tests were performed using a FAP (Friction After Polishing) machine in laboratory conditions. Macrotexture measurements were made on the surface of each sample using an Elatexure laser profile. In addition, three types of coarse aggregates were selected based on their resistance to polishing, which was determined on the basis of PSV (Polished Stone Value). Based on ANOVA, a significant influence of maximum aggregate size on both the friction coefficient and the MPD parameter was demonstrated. Along with the increase in the aggregate maximum grain size in EAC, the increase in MPD value was recorded. Despite of this fact, no effect of resistance to the polishing of aggregates with PSV from 48 to 52 on skid resistance was demonstrated. However, the decision to apply individual solutions should take into account road classification in the road network system, traffic volume and speed limits. [ABSTRACT FROM AUTHOR]

A road's performance is influenced by several factors. Owing to the limited availability of structural data, road agencies are forced to use rutting and fatigue cracking data as a substitute for structural bearing capacity to identify rehabilitation treatment options. However, this approach fails to assist in the development of investment strategies to reduce the life-cycle cost of the road asset nor will it maximise the safety of vulnerable road users. The introduction of traffic speed deflectometer (TSD) has made it more affordable for many road agencies to collect deflection data. The use of TSD has created a knowledge gap on methodology/mechanism as road agencies are yet to identify the best means of utilising and incorporating these structural data at network-level analysis. The structural deterioration model is a critical input in the pavement management system for predicting pavement rehabilitation needs. A practically implementable concept was adopted in this study to develop the models. These deterioration models were developed by utilising five years' time series TSD deflection data as a function of other readily available data. This study successfully established structural deterioration models that will enable road agencies to incorporate available TSD data in the pavement management system for developing investment strategies. [ABSTRACT FROM AUTHOR]

Aggregate-binder adhesiveness is a property that can affect the service life of asphalt pavements. In order to reduce the effects of the loss of adhesion between aggregates and binders over time, lime or amine-based anti-stripping agents are commonly used. The objective of this paper is to evaluate the impact of using an amine-based anti-stripping agent on the fatigue life of asphaltic pavements. Stiffness characterisation, the Simplified Viscoelastic Continuum Damage model, and the software FlexPAVE™ were used. Two different layered structures were analysed: one with a 0.10 m asphalt layer thickness, and another with a combination of two 0.05 m asphalt layers, with the same 0.10 m total asphalt layers thickness. The 10 years fatigue simulation was considered with 1,000,100 total ESALs traffic volume, single wheel loading of 40 kN, traffic speed of 60 km/h, and constant temperature of 20°C. It was concluded that mixtures with anti-stripping agent and/or granitic aggregate showed better fatigue behaviour than mixtures with neat binder and/or phonolitic aggregate. All investigated pavements showed bottom-up predicted crack initiation. It is more recommended to use the mixtures with amine-based anti-stripping agent on the bottom asphalt layer and mixtures with neat binder on the top layer. [ABSTRACT FROM AUTHOR]

Texture is required on pavements to provide safe and comfortable ride performance for users. This paper provides the first meaningful analysis of a long-term study of texture data obtained using TRACS (TRAffic Speed Condition Survey) at a site in the UK. TRACS data were collected annually, over a 2 km stretch of motorway from 1995 to 2019. A new data analysis approach utilising time series data with spectral analysis and spatial filtering procedures is presented. The results reveal that the approach enables legacy TRACS laser profile Sensor Measured Texture Depth (SMTD) data to be used to determine long term rates of change in road surface macrotexture. Thus, the technique has unlocked the potential for SMTD data collected annually for 7000 km of the Strategic Road Network in the UK, to inform road maintenance programmes by extrapolation. Additionally, results expose a systematic periodicity occurring each year within the SMTD data studied, corresponding to longitudinal oscillations with wavelengths between 33 and 62 m. The time-invariant periodicity of these oscillations suggests that it is 'imprinted' in the early life of the pavement. 'Imprinting' may theoretically arise with cyclic tyre loading applied by the suspension systems of heavy vehicles or during road construction. [ABSTRACT FROM AUTHOR]

A non-destructive testing method suitable for network-level pavement structural evaluation is the traffic speed deflectometer (TSD) test. However, the analysis of TSD measurements still needs a proper parameter back-calculation procedure, which requires an accurate and efficient forward calculation model. As a first step to solving this issue, a nonlinear spectral element model which can simulate TSD tests of asphalt pavements is developed. The model is used to investigate the characteristics and parameter sensitivity of the response of asphalt pavements caused by the TSD loading. The results indicate that the vertical deflection curve along the direction of movement observed on the asphalt pavement surface is slightly asymmetric, and the maximum deflection appears behind the centre of the loading area. In addition, the slope curve of vertical deflection is highly sensitive to the magnitude of the applied force, the moduli of the base layer and subgrade, and the thicknesses of the asphalt layer and base layer. Furthermore, the slope curve is relatively sensitive to the glassy modulus of the asphalt layer. Because of its good predictive capability and high computational efficiency, the proposed model has the desired characteristics to be used as the computational kernel for parameter back-calculation procedures of TSD measurements. [ABSTRACT FROM AUTHOR]

Pavement structural condition evaluation plays an important role in assessing rehabilitation needs and making prudent investment decisions. Recently the use of Traffic Speed Deflectometer (TSD), is being considered for pavement structural evaluation especially for network level pavement management applications. Among various TSD data measurements and indices, Surface Curvature Index (SCITSD), is a widely-used index for assessing the structural condition of the AC layers. Since asphalt modulus is temperature sensitive, measured deflections and consequently the computed SCITSD are also affected by pavement temperature at the time of testing. For consistent pavement evaluation, SCITSD computed across sections and over time should be adjusted to a reference temperature. This study presents an applied method for adjusting SCITSD to a reference temperature. The method was based on a model developed from a dataset built from responses computed with dynamic-viscoelastic analyses under TSD moving load in a wide range of pavement properties. The method was field evaluated with TSD data from three locations within the US and one location each in Europe and Australia. The results showed that the proposed method can reasonably adjust SCITSD to a reference temperature which enables its application in pavement structural assessment and subsequent use in pavement management activities. [ABSTRACT FROM AUTHOR]

Bearing capacity is a key index in pavement management systems in many countries, which reflects the essential material properties of asphalt pavements. Many stationary measuring methods have been undertaken in the past; current assessment of the bearing capacity tends towards fast and continuous measurements at traffic speed for a network analysis. The conventional evaluation using stationary loads do not represent real traffic loading condition; therefore the results will inevitably lead to discrepancies from reality. A specific computational program SAFEM based on semi-analytical finite element method is proposed to overcome the difficulty. The reliability and efficiency of the SAFEM is proved by verification with commercial FE software ABAQUS and field measurements. The variation tendency of the back-calculated bearing capacity has a quite good negative linear relation with the number of loading cycles in the experiment. The investigation shows this proposed assessment system is a feasible option for the fast and reliable analysis of the pavement bearing capacity at a network level for road administrations. [ABSTRACT FROM AUTHOR]

Two traffic speed deflection devices (TSDDs) that measure surface deflections at posted traffic speeds (up to 80–96 kph) were evaluated through a recent Federal Highway Administration project that included field trials at the MnROAD facility. Four geophones were embedded near the pavement surface to measure surface deflections during field trials at each of three MnROAD cells. In addition, the MnROAD facility counted with numerous other sensors such as strain gauges to measure pavement responses and thermocouple trees to collect pavement temperature at various depths. For the implementation of TSDDs in any network-level pavement management system, it is important to utilise a proper analytical model that can accommodate moving load and viscoelastic properties of pavement layers in the simulation of TSDD measurements. The 3D-Move software was chosen for this purpose. The viscoelastic properties used for the asphalt concrete (AC) layer include dynamic modulus and damping coefficient as a function of frequency relevant to the temperature at the time of the MnROAD field trials. The field trials and available data represented realistic field case scenarios to validate once more 3D-Move specifically for TSDD measurements. The proposed dynamic analytical model provided a good match with a variety of independent pavement responses that included surface deflection bowls (measured using embedded geophone sensors) as well as horizontal strains at the bottom of the AC layers (measured using MnROAD sensors). [ABSTRACT FROM PUBLISHER]

This article uses the limits of agreement (LOA) method to compare the falling weight deflectometer (FWD) and the traffic speed deflectometer (TSD), two pavement structural evaluation devices. The TSD measures deflection slope, whereas the FWD measures deflection. For this reason, measurements were converted to the surface curvature index (SCI) and the base damage index (BDI), which can be obtained from each device. The SCI and BDI agreement between the two devices was then evaluated. Although the relationship between the calculated SCI and BDI using both equipments is reasonably close to the line of equality, there is a significant variation and a bias in this relationship. For example, for an average SCI or BDI value of 300 μm, the bias was 30 μm (FWD values lower than TSD values), and the LOA was 380 μm. [ABSTRACT FROM AUTHOR]

Mechanistic-empirical pavement design guide (MEPDG) uses axle load spectra and the number of axle applications to characterise traffic loads for pavement design. Alberta Transportation installed weigh-in-motion (WIM) systems at six highway locations to characterise traffic loads in Alberta for MEPDG design. Seasonal and regional trends in traffic characteristics of the six WIM sites were investigated and compared with the default values in the MEPDG for the years 2009 and 2010. Truck traffic classification (TTC) and axle load distribution factor (ALDF) for the WIM sites showed deviations from the MEPDG defaults. Seasonal variations were also evident in the distribution of different classes of truck throughout the year. Differences are attributed to cold climate conditions and special truck traffic in Alberta because of local industries. Influence of the differences between site-specific traffic characteristics and the MEPDG defaults on the performance of both flexible and rigid pavements for Alberta conditions was investigated through a sensitivity analysis. It was found that the flexible pavement performance is sensitive to TTC and ALDF, and the rigid pavement performance is most sensitive to ALDF. [ABSTRACT FROM AUTHOR]

This study presents a revised approach to conceptualising and analysing data from the traffic speed deflectometer (TSD) which enables full deflection bowl predictions. The approach was successfully applied to TSD surface velocity measurements collected at seven test sites as part of recent Australian trials. More than 1500 deflection bowls produced from the TSD data were validated against approximately 600 40- and 50-kN falling weight deflectometer (FWD) deflection bowl profiles. Overall, the results showed a clear correlation between the shape and magnitude of deflection bowls predicted by both methods. Estimates of maximum deflection (d0) and structural curvature index (SCI300) from both methods were also compared, showing a strong correlation. The results suggest that the TSD device has significant potential to be used to collect measurements of pavement deflection bowls at highway speeds which are comparable with FWD deflection bowl measurements. [ABSTRACT FROM AUTHOR]