Relationship between Road Network Characteristics and Traffic Safety

The Transportation and Capital Improvement of the City of San Antonio, Texas Department of Transportation (TxDOT) and other related agencies often make several efforts based on traffic data to improve safety at intersections, but the number of intersection crashes is still on the high side. There is no one size fits all solution for intersections and the City is often usually confronted with doing best value option analysis on different solutions to choose the least expensive yet more advancements. The goal of this project was to obtain the relationship between road network characteristics and public safety with a focus on intersections; perform a thorough analysis of critical intersections with high crash incidents and crash rates within the city of San Antonio, Texas, and analyze key factors that lead to crashes and recommend effective safety countermeasures. Researchers conducted the following tasks: literature review, crash data analysis, factors affecting crashes at intersections, and the development of possible solutions to some of the identified challenges. Several variables and factors were analyzed, including driver characteristics, like age and gender, road-related factors and environmental factors such as weather conditions and time of day ArcGIS was used to analyze crash frequency at different intersections, and hotspot analysis was carried out to identify high-risk intersections. The crash rates were also calculated for some intersections. The research outcome shows that there are more male drivers than female drivers involved in crashes, even though we have more licensed female drivers than male drivers. The highest number of crashes involved drivers within the age range of 15 – 34 years; this is an indication that intersection crash is one of the top threats to the young generation. The study also shows that the most common crash type is the angle crash which represents over 23% of the intersection crashes. Driver’s inattention ranked first among all the contributing factors recorded. The high-risk intersections based on crash frequency and crash rate show that the intersection along the Bandera Road and Loop 1604 is the worst in the city, with 399 crashes and 8.5 crashes per million entering vehicles. The research concluded with some suggested countermeasures, which include public enlightenment and road safety audit as a proactive means of identifying high-risk intersections

Evaluation and Enhancement of Carbon Sequestration Potential of Existing Vegetation along Roadsides

The objectives of this study were to evaluate the vegetative composition and carbon sequestration potential of vegetation along a major roadway in Texas. Soil and vegetation were evaluated along IH-35 within Bexar County for composition and carbon content. Three 20 m transects were placed at each site and percent vegetative cover was estimated and above ground plant biomass, and soil was collected from three 0.25 m2 subplots along each transect. Plant and soil samples were analyzed for carbon content. Two non-native grasses, bermudagrass and King Ranch bluestem, were the dominant cover at all sites accounting for \u3e 90% coverage at several sites. Native plants were rare with only one species, western ragweed, accounting for \u3e 5% mean coverage at all sites. Carbon content of plant species was highest for bermudagrass (699 kg C ha-1) and King Ranch bluestem (401 kg C ha-1), and 6 of 7 sites contained significantly more carbon in non-native plants compared to native plants. The highest native plant carbon content was western ragweed with an average of 15 kg C ha-1. Mean soil carbon content ranged from 3.1 to 6.9 kg C m3 -1 among the sites, and significantly (P \u3c 0.05) greater amounts of carbon were recorded in the upper 0-10 cm compared to the 10-20 cm. The photosynthesis rates of Bermudagrass were significantly greater than rates recorded for King Ranch bluestem indicating the former species is highly adapted to hot semi-arid climate of central Texas, but King Ranch bluestem may gain a competitive advantage along roadways during the spring, fall and periods of increased precipitation. The total available area for the vegetation along the IH-35 highway in Bexar County is estimated to be approximately 81.7 ha (201.5 acres). We suggest the area between sites 5 and 6 (25.1 ha; 62 acres) are ideal locations for carbon sequestration using native plant communities including those with larger diameter woody stems such as trees

Multiscale approach for modeling hot mix asphalt

Hot mix asphalt (HMA) is a granular composite material stabilized by the presence of asphalt binder. The behavior of HMA is highly influenced by the microstructure distribution in terms of the different particle sizes present in the mix, the directional distribution of particles, the distribution of voids, and the nucleation and propagation of cracks. Conventional continuum modeling of HMA lacks the ability to explicitly account for the effect of microstructure distribution features. This study presents the development of elastic and visco-plastic models that account for important aspects of the microstructure distribution in modeling the macroscopic behavior of HMA. In the first part of this study, an approach is developed to introduce a length scale to the elasticity constitutive relationship in order to capture the influence of particle sizes on HMA response. The model is implemented in finite element (FE) analysis and used to analyze the microstructure response and predict the macroscopic properties of HMA. Each point in the microstructure is assigned effective local properties which are calculated using an analytical micromechanical model that captures the influence of percent of particles on the microscopic response of HMA. The moving window technique and autocorrelation function are used to determine the microstructure characteristic length scales that are usedin strain gradient elasticity. A number of asphalt mixes with different aggregate types and size distributions are analyzed in this paper. In the second part of this study, an elasto-visco-plastic continuum model is developed to predict HMA response and performance. The model incorporates a Drucker- Prager yield surface that is modified to capture the influence of stress path direction on the material response. Parameters that reflect the directional distribution of aggregates and damage density in the microstructure are included in the model. The elasto-visco-plastic model is converted into a numerical formulation and is implemented in FE analysis using a user-defined material subroutine (UMAT). A fully implicit algorithm in time-step control is used to enhance the efficiency of the FE analysis. The FE model used in this study simulates experimental data and pavement section

Harvesting Energy from Pavement – Electromagnetic Approach

Roadway pavements have a great potential to be a renewable energy source. Because they are continuously subjected to solar radiation and kinetic energy from passing vehicles. In this study, a prototype was developed to harvest passing vehicle kinetic energy by using electromagnetic technology. The prototype was fabricated by mechanical components including top plate, racks, pinions, one-way clutches, shafts, compression springs and generator. The prototype uses deflection generated by passing vehicles and converts it to rotations in shaft that triggers an embedded generator. A performance of the prototype in generating electrical power was evaluated with laboratory tests by using UTM and simulating traffic conditions. The output powers were measured by different magnitudes of the loads, times of loading and times of unloading. The experimental results show promising in generating power by the proposed prototype with a maximum average power of 3.21 mWatt