Hotspot Location Identification Using Accident Data, Traffic and Geometric Characteristics

Determining the criterion for critical limits is always one of the essential challenges for traffic safety authorities. The purpose of identifying accident hotspots is to achieve high-priority locations in order to effectively allocate the safety budgets as well as to promote more efficient and faster safety at the road network level. In recent years, human, vehicle, road and environment have been recognized as the three main effective elements of the road transportation in the occurrence of accidents. In the present study, with combining the parameters related to accidents, geometric parameters of the accident location and traffic parameters, hotspots were identified by using the superior methods of Poisson regression and negative binomial distribution and based on the combined criteria of frequency and severity of accidents and equivalent damage factors. Then using Time Series Models in ANN, result were compared and validated. The results of ANN models demonstrate that the frequency method of accidents tends toward places with high traffic volume. MATLAB and STATA software were used. Non-native plumbing, curvature, slope, section length and residential area had more significance, and their coefficients indicated the significant effect of these parameters on the occurrence of the frequency and severity of accidents in hotspot locations

Dynamic Analysis and Determination of Maximum Tensile Strain of Bottom Asphalt Concrete for Different Vehicle Velocities

Studying the stress, strain and deformation in pavement under traffic loads is one of the most important areas in pavement engineering. Tensile strain in the bottom of asphalt, leads to the most common type of failure (fatigue); therefore, it is an important parameter to be analyzed. In this study, the pavement structure has been analyzed and then for validation, the output in all elements and points were compared to the field results obtained from University of Pensylvania. The further studies were conducted by 3D program which indicated a good agreement with the results from field and the first finite element-based program. In static and quasi-static loadings, the maximum strain were observed exactly under the load center, while in dynamic loading, unexpectedly,themaximum value occurred behind the load center, and the distance increases by increase of vehicle velocity. This study includes the effect of load speed on tensile strain in asphalt sub-layer

Micro Simulation of the Elderly Population\u27s Effect on Iran\u27s Pedestrian\u27s Walking Flow

Since 1996 to 2006, Iran‟s population structure experienced considerable changes. During the mentioned period, the share of the population under 15 decreased from 39.6% to 28%. Considering this decrease, Iran‟s population was quickly guided to oldness which will have irreversible social and economical repercussions on the country‟s future progress. The main objective of this study is to estimate the effects of the elderly on the moving stream of the other pedestrians in Iran‟s sidewalks, which is done for the first time in Iran using the Micro-Simulation method. The Micro-Simulation model of pedestrians is a computerized simulation procedure in which the moving behavior of each pedestrian such as speed, path, and the direction is considered separately. According to the obtained results from this study, an increase in the percentage of the elderly population can lower the sidewalk\u27s level of service. Also, the decrease of the average motion speed and the free walking space for wider paths is not necessarily less than that of narrow paths; in a way that by increasing the width of a sidewalk, pedestrians‟ total average speed and the average walking space decrease up to a specific width and then, start to increase. This decrease in wider sidewalks is more than that in more narrow ones

Laboratory Evaluation of Alkali-Activated Slag Concrete Pavement Containing Silica fume and Carbon Nanotubes

Engineers and contractors strive to find the best type of concrete pavement for use in various conditions and applications due to poor performance of asphalt pavements in different climatic conditions, rapid erosion of pavement, poor durability and change in performance characteristics during operation and being non-economic during the period of operation compared to concrete pavements, and not being consistent with the sustainable development principles due to the use of oil-based adhesives. The most common use for portland cement is in the production of concrete that has led to production of greenhouse gases, including carbon dioxide, and global warming has been one of its consequences. More attention has been paid to alkali-activated concrete pavement as a solution because of these effects. The present study has investigated the behavior of alkali-activated slag (AAS) concrete pavement containing silica fume and carbon nanotubes (CNTs). For this purpose, silica fume and CNTs were used as additive for active alkali slag concrete, respectively. The flexural strength, compressive strength, tensile strength, chloride ion charge passed and durability against freeze-thaw cycles was decreased and water penetration was increased by adding silica fume and the use of CNTs in concrete has increased flexural strength, compressive strength, tensile strength, chloride ion charge passed and durability against freeze-thaw cycles and decreased water penetration. The addition of CNTs should have an optimum amount of 5%, so that the mechanical properties and durability of concrete will be decreased by adding more of this additive. The best mix design is for alkali activated slag carbon nanotubes (AASN5) sample, the properties of flexural strength (9%), compressive strength (15%), tensile strength (15%) and chloride ion charge passed (38%) of the AASN5 sample have increased compared to AAS for 28-day curing and penetration (33%) and weight loss decreased after freeze-thaw cycle

Numerical Analysis of Concrete Block Pavements and Comparison of Its Settlement with Asphalt Concrete Pavements Using Finite Element Method

Regarding time consuming properties and complex intervention of layers and different materials, it is better to replace laboratory based design and analysis of pavements with quick and powerful software including finite element, finite reduction software and etc. Using finite element software ABAQUS, at first, the paper investigated effects of changes of concrete block thickness in vertical stress and it was validated with experimental results. Also, using this software, effect of asphalt concrete thickness change was studied in vertical strain. And finally, results of finite element model were validated, using experimental data. Regarding that finite element analysis is suitable for crust environments and concrete block pavement does not have such environment, this research tends to compare these two types of pavements, using mathematical equations to analyze settlement. To do this, first, two models were designed, one for concrete block pavement and the other one for asphalt concrete pavement. Subgrade and base layers' models were the same in geometrical point of view and types of materials, but thickness of asphalt and concrete block pavement layers and bedding sand changed, alternatively and based on the obtained relations and diagrams, there has been a chance to equate indices of these two types of pavements

Evaluation of Mechanical Properties and Durability of Concrete Pavement Containing Electric Arc Furnace Slag and Carbon Nanostructures

The destructive effects of global warming have attracted attention to the optimal using of resources and recycling. Therefore, slag has been considered as a solution in various industrial sectors including the road construction. Also, among the new materials, cement carbon nanostructures which can improve the concrete mechanical properties and resistance are used. These nanostructures are produced through Chemical Vapor Deposition method during the cement production process on the type II cement. In this study, it is aimed to improve the mechanical properties and resistance of concrete pavements with slag and cement carbon nanostructures. The results showed that using 66% slag and 5% cement carbon nanostructures (SC66N5) have been shown the best performance in concrete pavements. Increasing the amount of slag and carbon nanostructures enhance the compressive strength, flexural strength, tensile strength, chlorine passing current and durability against freezing and thawing cycles, and decrease permeability and water absorption percentage. The results showed that in SC66N5 28-day sample, the compressive strength (52%), flexural strength (32%), tensile strength (53%), chlorine passing current (88%) and passing ultrasonic pulse velocity after freezing and thawing (7%) are increased with respect to the cement concrete sample. Furthermore, the permeability (46%), water absorption percentage (45%), weight loss after freezing and thawing cycles (78%) are reduced in comparison to the cement concrete sample. The results revealed that using slag and cement carbon nanostructures improve the durability of concrete pavements

Laboratory evaluation of Nano Al2O3 effect on dynamic performance of stone mastic asphalt

A part of different countries’ budget in the world annually is spent on the restoration and reconstruction of pavements damages. Hence, by increasing the quality of hot mix asphalt, the pavement researchers are constantly trying to improve the quality of hot mix asphalt, greatly reduce the incidence rate of damages in the roads and delay the incidence time as much as possible. Many studies show that the quality of hot mix asphalt can be improved by using additives. Nano Al2O3 is studied as an additive in this research and also, in order to improve the hot mix asphalt strength against the damages, the type of stone mastic asphalt is examined. Stone materials gradation used in this study is the average gradation proposed by Asphalt Pavement Regulation of Iran Roads (Publication 234) for stone mastic asphalt with a maximum aggregate nominal size of 20 mm. The bitumen consumed is bitumen 60–70 in Tehran Pasargad Oil Processing Complex. In order to prevent the draindown phenomenon in stone mastic asphalt which occurred according to the space between aggregates, the cellulose fibers with the amount of 0.3% hot mix asphalt weight are used to produce the hot mix asphalt. The effect of Nano Al2O3 additive on dynamic performance of stone mastic asphalt is investigated through dynamic creep test, wheel track test and indirect tensile fatigue test. Results show that addition of different percentages of Nano Al2O3 is capable to improve the dynamic performance of stone mastic asphalt, significantly. Keywords: Stone mastic asphalt, Nano Al2O3, Rutting, Dynamic creep, Fatigu

New Achievement for Prediction of Highway Accidents

Most research has been carried out about crash modeling but little attention to the urban highway. The candidate set of explanatory parameters were: traffic flow parameters, geometric infrastructure characteristics and pavement conditions. Statistical analysis is done by SPSS on the basis of nonlinear regression modeling and during the analysis, principal components are identified to assist the principal component analysis method and more important variables recognized that could exhibit best description of crash occurrence on the basis of available logics. Results indicate that the number of accidents per year increase with: length, pick hour volume and longitudinal slope whereas decreases with radius. Presented models show that crash occurrence is increased with the increase in each of section's length, pick hour volume and longitudinal slope variables whereas it is increased with the decrease of curvature. The remarkable result in this study was the effect of longitudinal slope variable on crash occurrence

Experimental Investigation of High Temperature Behaviour of an Asphalt Binder Modified with Laval University Silica Based on Multiple Stress Creep and Recovery Test

For experimental investigation of the high temperature behaviour of an asphalt binder modified with Laval university silica (LUS-1) nanostructured particle, four different asphalt binders were produced using a mixture of 2, 4, 6 and 8 wt% of this additive and a neat bitumen at 170 °C. The neat bitumen was yielded from crude oil refining and had a penetration grade of 85–100. After a 20 min vibration, the produced mixtures were mechanically mixed for 30 min in a high-shear homogenizer mixer with an angular velocity of 4500 rpm. Then, the modified binders and neat bitumen were subjected to multiple stress creep and recovery (MSCR) test, after the aging process in rolling thin film oven (RTFOT) test. The results of this study, which were in agreement with the results of the dynamic shear rheometer (DSR) test, indicated that LUS-1 could improve the high temperature behaviour of binders. The greatest improvement occurred using 4 wt% of LUS-1, where this improvement was more pronounced at high stress levels. Elevating the levels of stress and temperature led to diminished traffic grade and more viscous behaviour in asphalt binders modified with LUS-1