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Combined bridge-tunnel scenarios of driving on mountainous city expressways occur when bridges and tunnels frequently alternate during driving. The complex nature of these driving scenarios imposes crucial requirements on the drivers' eye movement characteristics. This paper attempts to clarify these characteristics using descriptive statistics and the box graph method, registering the pupil diameter, blink duration, fixation, saccades, and fixation loci at different tunnel locations, bridges, and ramps. Realistic driving experiments were performed on the road segment spanning from the Nanchang tunnel to the Liujiatai tunnel freeway in Chongqing, China. Eye movement data were collected for 21 drivers. The experimental results showed that, while driving in the tunnel, the maximal pupil diameter of the participating drivers was approximately 4.0mm as the driving mileage and the number of tunnels increased, and the maximal visual load on the drivers in the tunnel tended to be stable. At the second tunnel exit, the ramp, the middle section of the first bridge, and the third tunnel exit, the driving load was the highest, while the fixation duration was shorter for nighttime driving. The fixation duration was the longest for the diversion road of bridge B1 to the ramp during the day, and the fixation times were the longest at the beginning and end of the test road. The drivers more often paid attention to the speed dashboard while entering tunnels during daytime driving (compared with nighttime driving)., Author(s): Jingrong Bai [1]; Qinghai Lin (corresponding author) [2]; Huiyun Bi [1]; Boming Tang [1] 1. Introduction The special geographical environment and geological conditions of mountainous cities necessitate the use [...]

Noise from elevated railway bridges in urban areas has been causing severe environmental issues. To find the peak frequency of sound energy and thus develop targeted countermeasures for noise mitigation, policymakers need a better understanding of the noise characteristics of urban railway bridges during train passage. This study approaches this issue by combining transient dynamic analyses and acoustic finite element simulation. Our frequency characteristic analysis focused on two primary noise sources: wheel-rail noise and bridge-borne noise. We built a spatial noise model that predicts the radiated noise of urban railway bridges in both the active and planning stages. The results show that the wheel-rail noise peaked at 800 Hz, 1600 Hz, and 3150 Hz, while the bridge-borne noise peaked at 40 Hz, 50 Hz, 80 Hz, and 125 Hz. The validation results demonstrated that the developed noise spatial prediction model extended well to similar urban railway bridges. [ABSTRACT FROM AUTHOR]

At present, tuff aggregates as asphalt pavement mixtures have insufficient water damage resistance; hence, modifying and evaluating the related properties of tuff asphalt mixtures are necessary. In this study, cement and a liquid antistripping agent were selected as admixtures, and tuff and limestone mixtures without admixtures were selected as control. The surface energy for the SBS-modified asphalt polymers and aggregates in the mixtures was evaluated by using surface energy theory. The adhesion work and the spalling work of the polymer–aggregate interface was calculated, and a factor k was proposed to predict the water damage resistance of the tuff mixture with admixtures. The prediction values were compared with those of the macroscopic water stability test for the mixture. The results of this research showed that the factor k after adding admixtures was improved, and the increase range was from 7.14% to 47.62%. The admixture scheme with the best improvement was that with 2% cement content, in which the k value increased by 21.57% and 47.62% compared with that of the limestone and tuff mixtures without admixtures, respectively. The tested water stability indexes and the predicted factor k under different admixture schemes exhibited a good positive correlation, and the correlation equations were obtained by linear fitting. Thus, it was feasible to use the factor k characterizing the water damage resistance of tuff mixtures using surface energy theory. [ABSTRACT FROM AUTHOR]

The effect of filler modification on polyurethane (PU) properties was investigated by experimental and molecular dynamics simulation. Ultra-thin wearing course (PUTWC) was prepared using PU composite as a binder. The results indicated that, compared with composite with mineral powder, the tensile strength and elongation at break of PU composite (PUNC) containing CaCO3 increased by 32.7% and 15.8%, also exposed an appropriate viscosity. Stronger interaction energy and smaller free volume distribution existed in PUNC interface, which was obviously related to the PU soft segment. Additionally, prepared PUTWC using the single-layer paving method and PUNC of 1 kg. (m2)−1 showed high-skid resistance. [ABSTRACT FROM AUTHOR]

To improve the water damage resistance performance of a tuff asphalt mixture, a tuff mixture with cement and a liquid anti-stripping agent was used as the research object, and limestone and tuff mixtures without additives were selected as contrast samples. Through an improved boiling test and a water stability test before and after aging, the modification effect of the tuff mixture with additives of different types and contents on water damage resistance was evaluated to obtain the appropriate type and content of additives. On this basis, the other road performance measures of the selected mixture were further evaluated by immersion rutting and beam bending tests to verify the modification effect of the additive on the tuff mixture. Results showed that adding the appropriate cement content to the tuff mixture provided excellent resistance to the water damage effect. An optimal content of 2% cement additive in the mixture was obtained, and its high-temperature anti-rutting and low-temperature bending performance were also verified. Adhesion between tuff aggregates and asphalt polymer under water conditions was significantly improved and close to that of limestone aggregates. The modification effect of water stability after mixture aging was better than that of the anti-stripping agent. The residual stability and freeze–thaw splitting strength ratio of 2% cement content mixture were increased by about 21.5% and 16.7%, respectively, compared with those of the tuff mixture control. [ABSTRACT FROM AUTHOR]

Polyurethane mixture, made of waste rubber particle, aggregate, and polyurethane adhesive, has low raveling resistance which affects the durability of the mixture. The objective of this study is to enhance the raveling resistance of polyurethane mixture. The content of polyol in the hydroxyl component was determined by Fourier transform infrared spectroscopy. The suitable curing conditions for polyurethane adhesive to enhance the raveling resistance were selected by the orthogonal experiment and mechanical tests. The relationship of the raveling resistance with crosslink density and elastic modulus was tested and calculated through the wear test. The results showed that when the ratios of the isocyanate component to the hydroxyl component were 1:3.2, 1:6.3, and 1:9.5, respectively, the isocyanate component was excessive. The ranking of the significance of the influence factors, from high to low, was first the curing temperature, then curing time, and finally the blending ratio; within the ranges of blending ratio, curing temperature, and curing time selected in this study, the appropriate blending ratio was 10:2, and the curing time was 6 h. For the polyurethane mixture involved in this study to obtain high raveling resistance, if a crosslinking agent or a new polyurethane adhesive is added, the tensile strength and tensile elastic modulus should be in the range of 3.02 to 3.27 MPa and 5.50 to 6.02 MPa, respectively; when using the FS2 polyurethane adhesive directly, the suitable curing conditions for the mixture are 90 °C and 6 h or 80 °C and 6 h. The results from this study could be beneficial for obtaining a high raveling resistance for the polyurethane mixture. [ABSTRACT FROM AUTHOR]

Research on the aging process of styrene-butadiene-styrene block copolymers (SBS) block copolymers modifier has practical significance in guiding the recycling of SBS-modified asphalt pavement. The objective of this study is to investigate the aging process of SBS modifier under various oxygen and thermal conditions to address the variations of physical properties and chemical reaction during the service life of recycled asphalt pavement (RAP). In the proposed testing process, SBS modifier was thermal oxidative and vacuum thermal aged at different temperatures and time prior to blending with base asphalt to prepare SBS-modified asphalt. SBS modifier was first dissolved by carbon tetrachloride (CCl4) and then tested through infrared (IR), gel permeation chromatography (GPC), and thermogravimetric (TGA) tests to investigate the variations on microstructure and chemical compositions of aged SBS modifier. The effect of aged SBS modifier on performance of SBS-modified asphalt was evaluated by comparing the mechanical and chemical properties of base and SBS-modified asphalts. Based on the results of the experimental program, appearance variation, modifying effects, and chemical reaction of SBS modifier under oxygen condition were obviously different from that of vacuum condition. The chemical reaction of SBS modifier was not significant at vacuum and high temperature condition, instead, a small amount of degradation was observed. Degradation of mechanical performance of SBS-modified asphalt was mainly caused by aging of base asphalt. Therefore, the SBS modifier in the RAP was suggested to be considered in the mixture design. [ABSTRACT FROM AUTHOR]

With the development of the highway industry and new materials, long-afterglow luminescent material as a new energy storage and environmental protection material has gradually been applied to night lighting. In this study, SrAl2O4:Eu2+ , Dy3+ long-afterglow materials were prepared by the solid-state reaction method. The luminescent properties were improved by changing the process parameters. The single-factor test results indicated that the luminescent properties were highest when flux content, calcination temperature, calcination time, and doping ratio of Eu and Dy were 5%, 1,300°C, 2 h and 1∶1 , respectively. Then, long-afterglow materials with high luminescence were prepared by adding a pore-forming agent. The structural characteristics and optical properties of the products were analyzed. X-ray diffraction (XRD) and scanning electron microscopy (SEM) analysis indicated that the addition of pore-forming agent did not change the crystal structure of the material but changed the surface morphology of the long-afterglow materials. The surface morphology of the products changed from flat and dense to a convex structure after adding pore-forming agent, and some connected pore structures were produced. The afterglow performance of products was continuously improved with the increase of pore-forming agent content. Finally, luminescent coatings were prepared by combining with fluorine-containing resin, and the performance was studied. The stability of luminescent coatings decreased with the increase of the filler:binder ratio, and the best ratio was 0.5∶1. The luminous performance of coatings was best when the amount of long-afterglow phosphor was 40%. The luminescent coatings had good adhesion with the road surface, and the luminescence could last for more than 7 h in a dark environment. [ABSTRACT FROM AUTHOR]

As classical traffic noise prediction models lack a deeper consideration of the impact of the gradient, the characteristics of longitudinal gradients from multiple roads were collected as data in the mountain city of Chongqing county, which was chosen as the entry point, to study the noise characteristics for a wide range of road gradients and to build a traffic noise prediction model based on artificial neural networks (ANNs). The field data consisted of traffic volumes, heavy-vehicle ratios, average vehicle speeds, road gradients, and corresponding equivalent sound pressure levels. An optimal ANN model was determined and compared with two classical models. The results demonstrated that a one-hidden-layer ANN model was suitable for traffic noise prediction in mountain cities and presented better predictive performance than the conventional models. The best-performing ANN model yielded a determination coefficient of 0.9447 and a mean-squared error of 0.2708 dBA. Moreover, this study confirmed that road gradients were significant for constructing traffic noise prediction models. [ABSTRACT FROM AUTHOR]

In this paper, a comprehensive study of structural evaluation methods for jointed concrete airfield pavements is presented. A specially prepared concrete test pavement, consisting of six slabs with different size voids beneath the slabs at corners incorporated by variably spaced dowel joints, is loaded by the falling weight deflectometer (FWD) test system. By analyzing these FWD measurements with the finite element model, the usefulness of the FWD as a tool for measuring various important pavement properties is assessed. Based on the deflection basins measured by FWD, the resilient modulus of the foundation can be calculated, load transfer efficiency at joints of pavement can be determined, and the size of voids beneath the slab can be detected. Field measurements made at an in-service airfield pavement indicate that the FWD is a suitable device for the structural evaluation of jointed concrete airfield pavements.

The application of photocatalysts on pavement engineering to degrade automobile exhaust has become a hot topic for researchers. However, the effect of photocatalysts on pavement materials has not been fully investigated. The primary purpose of this study is to explore the effect of a typical photocatalyst titanium dioxide (TiO2) on the chemical structure and properties of asphalt through laboratory experiments and molecular dynamics (MD) simulation. Performance tests indicated that the physical properties of asphalt modified by TiO2 changed more significantly compared with that of calcium carbonate (CaCO3) and silica (SiO2), which might be due to the smaller particle size of TiO2. Atomic force microscopy (AFM) and Fourier infrared spectrum (FI-IR) analyses demonstrated that the addition of TiO2 resulted in a smoother asphalt surface and a disappearance of the bee structure. Using TiO2 would not accelerate the aging process of asphalt. Moreover, the MD simulation results indicated that a more significant interaction existed between TiO2 and asphalt than that of CaCO3 and SiO2 , which resulted in a tighter asphalt molecule and smaller free volume distribution in the TiO2-asphalt system. [ABSTRACT FROM AUTHOR]

The properties of asphalt and aggregate in the warm-mix asphalt (WMA) containing recycled asphalt pavement (RAP) are critical to the mixture performances. This study quantified the effects of the morphological properties of WMA-containing RAP through the gray correlation analysis. The properties of asphalt and aggregate involved in this study included RAP content, two-dimensional morphological properties of recycled coarse aggregate, three-dimensional angle of recycled coarse aggregate, and surface free energy of recycled asphalt. The high-temperature performance represented by dynamic stability, low-temperature indicated by maximum bending strain, and moisture susceptibility characterized by the tensile strength ratio were chosen as the criteria for evaluating the impacts of different factors. The results showed that the RAP content had the greatest influence on high-temperature performance, followed by recycled asphalt's surface free energy (SFE), and aggregate sphericity. The irregular shape factor of aggregate particles significantly influenced the mixture's low-temperature properties. The SFE of asphalt was pivotal to the moisture susceptibility, and samples with higher SFE of asphalt presented better moisture damage resistance. [ABSTRACT FROM AUTHOR]

Mountainous freeways with high bridge and tunnel ratios are a new type of road that rarely contain many special road sections formed by various structures. The crash characteristics of the road are still unclear, but it also provides conditions for studying how various road environments affect traffic. In view of the various structures and differences in the driving environments, a scenario-based discretization method for such a road was established. The traffic-influence areas of elementary and composite structures were proposed and defined. Actual data were analyzed to investigate the crash patterns in an entire freeway and in each special section through statistical and comparative research. The results demonstrate the applicability and validity of this method. The crash rates were found to be the highest in interchange and service areas, lower in ordinary sections, and the lowest in tunnels, being mostly attributed to collisions with fixtures. The crash severity on bridges and bridge groups was significantly higher than that on the other types of road sections, being mostly attributed to single-vehicle crashes. The annual average daily traffic and driving adaptability were found to be related to crashes. The findings shed some light on the road design and traffic management implications for strengthening the traffic safety of mountainous freeways. [ABSTRACT FROM AUTHOR]

The application of photocatalyst in pavements has received comprehensive attention in recent years due to its ability to decontaminate nitrogen oxides (NOx). However, it's remarkable that NOx also accumulated extensively in parking lots. The purpose of this study is to develop a movable photocatalytic plate (remarked photocatalytic KT plates) coupled with high activity to purify NOx. Firstly, the type of photocatalytic KT plates was determined according to NO removal experiment in laboratory. Then the plates were employed in the parking lots for removing NOx. One sample T-test, normality test and paired sample T-test methods for NOx concentration variation were conducted to determine the appropriate comparative means of dates under both dark and illuminated conditions. The difference of NOX concentration between dark and illuminated conditions was obtained to evaluate the photocatalytic removal efficiency. The results indicated that NO removal efficiency in laboratory and parking lots were 51.31% and 9.2%, respectively. [ABSTRACT FROM AUTHOR]

The service radius of public parking garage is related to the supply of parking spots and parking behavior characteristics of drivers. However, the empirical and statistical methods in the optimization of public parking garage have limitations. Based on the theory of value engineering and satisfaction, an optimization model for public parking garage service radius is established, which satisfies the requirements of both drivers and owners. Then, an amended model is proposed by using accessibility theory and the principle of moment balance. This model, in consideration of city resistance and walking impedance, is modified from the circular service scope to an irregular polygon, which is more suitable for the actual situation. Finally, the method is verified by a practical example. The results suggest that the optimization model of the service radius and the optimization method of service scope can not only balance the needs of drivers and public parking garages’ owners, but also improve the operation efficiency of parking garages, so that they are more fit for the actual situation of parking service areas. This paper provides new ideas and methods to determine public parking garage service radius and service scope. [ABSTRACT FROM AUTHOR]

In the experiment, a heat-reflective coating (HRC) was applied to the surface of asphalt pavement. The coating temperature reduction principle and the mechanism to mitigate the urban heat island effect (UHI) were explored by analyzing the material characteristics and features of atmospheric absorption spectrum. HRC features a good waterproof ability, strong oil resistance, abrasion resistance, and aging resistance. When it was painted on the surface of the dense-graded asphalt concrete, the pavement temperature could be reduced by approximately 9°C in hot seasons. The comprehensive pavement performance was evaluated through the following tests: antiskid, accelerated abrasion, freeze-thaw cycle, and permeability. The results show the asphalt concrete pavement with adopting HRC has a strong abrasion resistance, a good resistance to temperature fluctuation, and significantly reduces water damage. The skid-resistant ceramic granular should be added in the dense-graded asphalt pavement with HRC, which was shown to greatly improve the antiskid capability. [ABSTRACT FROM AUTHOR]