Teresa Iuele

Recycling PEMs back to TLPAs: Is that Possible Notwithstanding RAP Variability?

Porous European mixes, PEMs, are porous asphalts which when compacted have an air void content usually in excess of 20%. PEMs points of strength are reduction of splash and spray, mitigation of outdoor noise, optimization of skid resistance at high speeds in wet conditions. Conversely, PEMs have quite low bearing properties, clogging, variation of volumetrics over the time, variation of noise, texture, friction, and permeability performance over the time. Furthermore, at the end of their lifecycle many issues arise: RAP variability, uncertainties on the potential for high percentage recycling, potential for recycling a surface layer back to a surface layer. Based on the abovementioned facts, objectives and scopes were then focused into the analysis of the feasibility of a two-layer porous asphalt (TLPA) by recycling from-PEM RAP, when highly variable rap stockpiles are involved. The following main issues were addressed: mitigating the clogging and its related consequences (acoustic and drainability performance over the time); preserving traditional (bearing properties, skid resistance) and premium (silentness, drainagebility) performance; recycling high percentages of from-PEM RAP. Materials selection was followed by mixtures production. Traditional and advanced tests on RAP and recycled mixes were carried out. RAP variability was examined and a method for facing its consequences was proposed. Mechanical performance was adequate and environmental compatibility was achieved. Functional performance resulted very promising. Results are encouraging about the possibility of achieving a satisfactory level of surface performance. Practical applications and perspectives in rehabilitation, maintenance, and research are outlined.

Effect of Asphalt Mix Properties on Surface Texture: An Experimental Study

Pavement surface characteristics play an important role in accident occurring, especially in wet conditions: the optimization of surface performance starting from hot mix asphalt (HMA) design phases is a fundamental requirement in road construction techniques. Although such relevance, the prediction of surface properties based on HMA composition and construction still calls for further research. Indeed, there is not a clear framework for a mix design oriented to surface properties. In the light of the abovementioned facts authors efforts were focused into the analysis of the most significant factors influencing pavement surface macrotexture, by analyzing the main variables of existing macrotexture prediction models. Many experimental mixes were designed and produced. Some statistical correlations between macrotexture data and mixes grading and volumetric properties were also carried out. Outcomes of this study are expected to benefit both practitioners and researchers.

Methodological Approach for Evaluation of Roundabout Performances through Microsimulation

In the literature, there are many methodologies that allow the evaluation of roundabout performances (Capacity, Levels Of Service, etc.): analytical models (HCM, HBS etc.), statistical models (TRRL, SETRA) etc. Each technique considers some aspects of the roundabout in comparison to others (geometric elements, vehicular flow and behavioral parameters). Obtained results are often not comparable among themselves because of distinctive peculiarities of each method. Today, the best way to solve this problem is by using a refined simulation software of vehicular circulation. However, along with a more and more refined analysis of microsimulation software algorithms, it is frequently necessary for each user (researcher, engineer, planner, etc.) to know the real sensitivity of these packages with regard to the most important key parameters. In this paper the Authors introduce the results of a wide survey conducted on an ample range of virtual roundabout scenarios by the use of a modern simulation software. Each scenario describes a fixed roundabout phenomenon using the following variables: geometric elements (inscribed circle radius, circulatory roadway, central and splitter islands etc.); characteristics of the traffic flow (dynamic traffic assignment, approach speed, circulatory speed and reduced speed zones, etc.); behavioral features (priority rules, minimum gap, minimum headway, etc.). The results are presented from the evaluation of stop-line delays.

Permeable Wearing Courses from Recycling Reclaimed Asphalt Pavement for Low-Volume Roads: Optimization Procedures

The recycling of reclaimed asphalt pavement (RAP) in hot-mix asphalt (HMA) is an important opportunity in regard to transportation infrastructure construction and maintenance because it helps to achieve more sustainable road transport systems (reduction of waste production and reduction of resource consumption). In particular, totally recycled HMAs can be a good alternative for road paving even if performance can be an issue. As is well known, the type of low-volume road pavement (gravel, coarse rocky soil, crushed aggregate, cobblestone, concrete block, or some type of bituminous seal coat or asphalt pavement) depends on traffic volume, native in-place soils, and the need to control surface and depth erosion. The objectives and scope of this research were confined to the formalization of strategies and technical procedures for recycling RAP from porous asphalt concretes to obtain permeable wearing courses for low-volume roads. Different solutions were investigated. High percentages of RAP were used in the recycling process, and traditional and advanced tests on RAP and recycled mixes were carried out. RAP variability was examined, and a method for facing its consequences was proposed. Mechanical performance was adequate. Recycling porous European mixes could be a proper way to achieve environmental sustainability in pavement construction, as the functional performance results are very promising and encouraging. Practical applications and perspectives in rehabilitation, maintenance, and research are outlined.

Conversion of a Semi-two Lanes Roundabout into a Turbo-roundabout: A Performance Comparison

In the last years, as regards the functional design of at-grade intersections, near to classic layouts (signal-controlled junctions, roundabouts, etc.) a new solution has born: the “turbo-roundabout”. It is a canalized multilane oval intersection with a non-traversable or partially traversable center island and with a spiral circulatory carriageway. This kind of roundabout is also characterized by a predictable lane use: some direction flows are physically separated by curbs. Several roundabouts with spiraling circular carriageways were built in northern Europe (in particular in Netherlands) and they have further allowed to extend the notable advantages of this functional solution against multilane roundabouts, such as: 1) no lane changing on the circulatory carriageway; 2) no need to yield to traffic flow on more than two lanes; 3) low driving speed along the through movement because of raised lane dividers and, consequently, a high reduction of accident risk. In this paper a careful literature review on turbo-roundabouts is proposed. Furthermore, the Authors examine the potentialities offered by the transformation of an existing semi-two lanes roundabout into a “virtual” configuration of a turbo-roundabout. In particular, they also evaluate and compare the performance parameters in the two configurations by using a microsimulation software. The case study roundabout is placed in the city of Cosenza (Southern Italy) and it is characterized by great problems of congestion during peak hours. Experimental measures of traffic flows (O/D matrixes), critical gaps, queue lengths and approaching and circulating speeds represent input data for calibration procedures. Afterwards, derived calibration parameters are used as input variables for the new configuration of the intersection as a turbo roundabout. The Authors highlight that the conversion of the existing roundabout into a virtual turbo roundabout determine an increase of capacity together with a minimization of the queue lengths.

Experimental Investigation on Surface Performance and Acoustic Absorption

Porous European mixes and open-graded friction courses are wearing courses with well-known advantages in terms of noise reduction due to the balance between generation factors (surface texture) and absorption properties. Unfortunately, noise-oriented mix design still calls for further research and the relationship between composition and acoustic performance is mainly unknown. Consequently, the objective of this paper was to study the relationship between acoustic absorption coefficient and pavement surface performance (surface texture and drainability). The acoustic absorption coefficient was measured according to the ISO 13472-1. Acoustical absorption coefficients were analysed by taking into account contract specifications and requirements. Surface texture was investigated according to the standards ISO 13473-1; ISO/CD TS 13473-4; ISO 13473-3. In order to assess the overall state of the surface, also drainability was measured in the same points. Results were compared and analysed in terms of averages and standard deviations, studying in-depth how acoustic absorption properties vary as a function of surface texture and drainability, for a given friction course. A theoretical framework based on texture and acoustic properties was formulated. Results showed that the maximum acoustic absorption (f = 800–1000 Hz) was well correlated with drainability and Sand Height; some texture indicators (profile-based) resulted well correlated with several parameters derived from acoustic absorption spectra and/or macrotexture performance.

Surface Performance Characterization of Single-Layer Surface Dressing: A Macrotexture Prediction Model

Bituminous surface treatments (seal coats, chip seals, etc.) are pavement wearing courses created using asphalt binder and aggregate. They can be applied to an existing pavement or to a base course. They can act as a waterproof, skid resistant layer, sealing cracks and raveled surfaces and increasing reflection properties of road surfaces. Their expected life ranges from two to five years and are widely used in flexible pavements maintenance and rehabilitation because of reduced costs and the easiness of application. One of the most important characteristics of bituminous surface treatments is their macrotexture (initial and over time). Indeed, it affects tire-pavement interaction in wet and dry conditions and can interact with other characteristics and distress (aggregate embedment, loss of cover aggregate, streaking, bleeding, etc.). This paper focuses on the evaluation of surface performance of laboratory slabs, produced through a single-surface dressing. Macrotexture depth was measured by the Sand Patch method. A laser profilometer was also used to survey slabs texture and both aggregate descriptors and texture levels were evaluated. Finally, skid resistance and drainability data were measured by means of the British Pendulum Tester and the Belgian Permeameter, respectively. Aggregates of different size were selected in order to investigate on the relationship between aggregate dimensions and surface performance. A model was developed, implemented and validated. Results are expected to benefit both practitioners and researchers.

Erratum to “Investigating the Transferability of Calibrated Microsimulation Parameters for Operational Performance Analysis in Roundabouts”

Microsimulation models are widespread for the analysis of roundabouts operational performance providing realistic modelling of vehicle movements. These models are based on many independent parameters to describe traffic and driver behaviour, which need to be calibrated in order to better match field data. In practice, despite the well-recognized importance of calibration and validation processes, simulation is conducted under default values because of difficulties in field data collection and deficiency in available guidelines. These issues can be faced by using transferability methodologies that allow applying the parameters calibrated for a case study to other similar locations. Therefore, this paper investigates the suitability of the transferability procedure adopting both the application-based and estimation-based approaches, by considering two roundabouts and a microsimulation tool. A Genetic Algorithm technique was used to determine the best estimates of these model parameters. After that, the authors compared field-measured with simulated queue lengths, considering four different scenarios. The results show that the application of Wiedemann 99 parameters calibrated for the first case study to the second one allows reducing the RMSNE more than 50%, thus confirming an acceptable level of transferability of these parameters between the two case studies.