Relationship Among Traffic Intensity, Intersection Geometry, And Users' Behavior

Even though the parts of a road traffic system are interrelated and influence each other, the problems of road safety are directly associated with the geometry and the equipment of streets, particularly in sites where conflicting movements exist, as at intersections. Principles and measures are discussed aiming to decrease the intensity of conflicts in intersections. The examination of accident causes has to be performed in homogeneous parts from various options (geometry of the alignment, pavement condition, traffic conditions, road’s equipment and environment, presence of grade intersections and entries in settlements) and not at individual sites. In the city of Xanthi, Northern Greece the number of accidents with victims is not high, due mainly to the behavior of road users, who does not raise the private car in a role of protagonist. The geometry of road network is susceptible to improvements in relatively few intersections; however interventions could be made for the control of its operation with careful signing and recantation of unfavorable impacts from forced signaling choices

Characterization of pavement subgrade soil using gyratory compaction

A parameter used to carry out the quality control of unbound compacted soil materials is the maximum dry unit weight obtained from a standard or modified Proctor test. However, these tests are far from simulating the field compaction mechanism produced by roller equipment. The gyratory compactor has been put forward as a new laboratory equipment to determine the compaction curves in the Highway Construction and Pavements Laboratory accommodated in the Polytechnic School of Democritus University in Xanthi Greece. Results of Proctor and modified compaction curves as well as those obtained from the gyratory compactor are presented in the current paper. The controlled variables in the gyratory compactor were the vertical pressure, the gyration angle, and of course the number of gyrations. The compaction curves are more or less similar disregarding the rate of gyration and gyration angle. The dynamic compaction yielded better results compared to those obtained by the gyratory compactor. The difference between the two compaction modes was greater at low moistures. Three different moistures were used. In any case, the dynamic method led to higher dry density values. California Bearing Ratio specimens prepared with dynamic or gyratory compaction have lower values with an increase in moisture contents and were generally greater in the case of dynamic compaction

Design of flexible road pavements as affected by drainage conditions

Road pavement use is determined primarily by the vehicle type that will use the facility. Climatic conditions affect the behavior of pavement materials, as well as the sizes of traffic loads. The relative strength loss in a layer due to its drainage characteristics and the total time it is exposed to near-saturation moisture conditions is represented by drainage coefficients. The Transportation Laboratory of Democritus University of Thrace in Xanthi Greece has developed an algorithm for a computer-based procedure towards the calculation of the layer thickness of flexible pavements. The design equation used is that described by the American Association of State Highway and Transportation Officials. The present work deals with the effect of drainage on the total thickness of the structure as it directly influences the cost of large infrastructure projects like roads. The output of different cases solved is presented in table and schematic form. Changes in technology related to pavement design and construction practices will necessitate revisions to currently used computing techniques. There is a need for computerized methodologies for thickness design of flexible asphalt pavements (granular base course) for a wide variety of pavement uses providing users the capability to conduct structural analysis of special pavement structures. Improvements in computing times which will affect in a way the cost of computerized methods available to engineers are to be suggested in the near future. Empirically supported pavement designs used nowadays in Greece require modifications based on regional experience and on a better assessment of the drainage conditions prevailing in each area crossed by a roadway project. Since design considerations constantly change, it is obligatory to shift towards more sophisticated design methods

Imaging RAGE expression in atherosclerotic plaques in hyperlipidemic pigs

Background: Receptor for advanced glycated end product (RAGE) expression is a prominent feature of atherosclerosis. We have previously shown in apoE null mice uptake of a radiolabeled anti-RAGE antibody in atherosclerotic plaque and now evaluate RAGE-directed imaging to identify advanced plaques in a large animal model. Methods: Nine hyperlipidemic (HL) pigs were injected with 603.1 ± 129.5 MBq of 99mTc-anti-RAGE F(ab′)2, and after 6 h (blood pool clearance), they underwent single-photon emission computed tomography/computed tomography (SPECT/CT) imaging of the neck, thorax, and hind limbs. Two HL pigs received 99mTc non-immune IgG F(ab′)2, and three farm pigs were injected with 99mTc-anti-RAGE F(ab′)2. After imaging, the pigs were euthanized. The aorta from the root to bifurcation was dissected, and the innominates, proximal carotids, and coronaries were dissected and counted, stained for H&E and RAGE, and AHA-classified. Results: On pathology, 24% of the arterial segments showed AHA class III or IV lesions, and these lesions were confined almost exclusively to coronaries and carotids with % stenosis from 15% to 65%. Scatter plots of %ID/g for class III/IV vs. I/II lesions showed almost complete separation. Focal vascular uptake of tracer visualized on SPECT scans corresponded to class III/IV lesions in the coronary and carotid vessels. In addition, uptake in the hind limbs was noted in the HL pigs and corresponded to RAGE staining of small arteries in the muscle sections. Correlations for the vascular lesions were r = 0.747, P = 0.001 for %ID vs. %ID/g and r = 0.83, P = 0.002 for %ID/g vs. % RAGE staining. Conclusions: Uptake of radiolabeled anti-RAGE antibody in coronary and carotid fibroatheroma and in the small arteries of the hind limbs in a relevant large animal model of atherosclerosis supports the important role of RAGE in atherosclerosis and peripheral artery disease as a target for imaging and treatment

Significance of Fines in Hot Mix Asphalt Synthesis

According to their size, aggregates are classified in coarse grained, fine grained, and fines. The determination of fines content in aggregate materials is very simple and is performed through the aggregate washing during the sieving procedure to define the gradation curve. The very fine material consists of grains having a size lower than 63 μm. The presence of fines directly influences the composition and performance of concrete and asphalt mixtures (e.g. asphalt content, elasticity, fracture). The strength and load carrying capacity of hot mix asphalt (HMA) results from the aggregate framework created through particle-particle contact and interlock. Fines or mineral filler have a role in HMA. The coarse aggregate framework is filled by the sand-sized material and finally by the mineral filler. At some point, the smallest particles lose contact becoming suspended in the binder not having the particle-particle contact that is created by the larger particles. The overall effect of mineral filler in hot mix asphalt specimens has been investigated through a series of laboratory tests. It is clear that a behaviour influenced by the adherence of fines to asphalt film has been developed. The optimum bitumen content requirement in case of stone filler is almost the same as that for fly ash. It has been found that the percentage of fly ash filler is crucial if it exceeds approximately a value of 4%

Influence of aggregate gradation on hma mixes stability

The load transfer capacity of pavements is to a great extend influenced by aggregates. About 85% of the total volume of hot mix asphalt (HMA) mixtures consists of aggregates; thus, they are greatly influenced by aggregate properties like angularity (shape), roughness (texture), and gradation. Aggregate gradation controls the structure of voids. Current specifications for aggregate properties in HMA pavements require the aggregate blend to fall within a specified range of gradation values. Although the abovementioned requirement has ensured the construction of high quality HMA pavements, the properties are largely empirical and they are not based on performance-related tests. Marshall Stability is in principle the resistance to plastic flow of cylindrical specimens of a bituminous mixture loaded on the lateral surface. It is the load carrying capacity of the mix at 60oC. Aggregates with different gradations from the broader area of Xanthi, Northern Greece, have been used to prepare specimens for stability testing of hot asphalt mixtures in the laboratory. The research focused on the evaluation of the influence of aggregates in the overall stability characteristics of the mixtures. The maximum stability value has been obtained with an open-graded mixture having 5% asphalt and aggregate size 2.36 mm. However, the stability of the dense graded mixture is higher than this maximum value