Ranking and Determining the Factors Affecting the Road Freight Accidents Model

The tremendous growth of population, particularly in developing countries, has led to increased number of travels, especially those with load and freight specifications. Hence, expanding the present facilities or developing new networks or systems concerning freight and transportation is an essential issue. Among the various transportation systems, road freight has secured a significant place in sub-urban transportation, as it is responsible for transporting loads, decreasing transportation costs, and increasing the safety of highway users. Besides these advantages, poor and nonstandard design and performance of sub-urban highways and transport fleet and equipment leads to the increased number of accidents and inefficiency of these facilities.  Based on these facts, the primary aim of the present study is to probe into the factors affecting road freight accident severity. For this purpose, the data obtained from road freight accidents occurring in 2016, 2017, and 2018 in Gilan Province, Iran, were used for analyzing the frequency, ranking and determining the factors, and creating models for accident severity. The results indicated that in accordance with the accident severity model in 2016, several factors such as the season of autumn, daytime light, drivers aged from 18 to 60, and pickup trucks have impacted the on-road freight accident severity. While, in 2017 the severity was affected by factors like rural road, freight trucks, non-faulty passenger cars, motorcycles, and pedestrians. When considering the effective variables in 2018, it was  found that such factors as the accident time (usually occurring between 12 p.m. to 6 p.m)., rural and major roads, freight trucks, non-faulty motorcycles, and the careless driving without due care and attention to the front were the variables affecting road freight accidents. Moreover, not following safety guidelines during freighting is the most effective variable in road freight accidents

Time transfer and significance of vertical land motion in relativistic geodesy applications: a review paper

Determination of the Earth’s gravity field and geopotential value is one of the fundamental topics in physical geodesy. Traditional terrestrial gravity and precise leveling measurements can be used to determine the geopotential values at a local or regional scale. However, recent developments in optical atomic clocks have not only rapidly improved fundamental science but also contributed to applied research. The latest generation of optical clocks is approaching the accuracy level of 10−18 when facilitating atomic clock networks. These systems allow examining fundamental theories and many research applications, such as atomic clocks applications in relativistic geodesy, to precisely determine the Earth’s gravity field parameters (e.g., geopotential values). According to the theory of relativistic geodesy, the frequency difference measured by an optical clock network is related to the gravity potential anomaly, provided that the effects of disturbing signals (i.e., tidal and non-tidal contributions) are filtered out. The relativistic geodesy principle could be used for a practical realization of global geodetic infrastructure, most importantly, a vertical datum unification or realization of height systems. This paper aims to review the background of relativistic (clock-based) geodesy and study the variations of optical atomic clock measurements (e.g., due to hydrology loading and land motion)

Quality description in GPS precise point positioning

GPS processing, like every processing method for geodetic applications, relies upon least-squares estimation. Quality measures must be defined to assure that the estimates are close to reality. These quality measures are reliable provided that, first, the covariance matrix of the observations (the stochastic model) is well defined and second, the systematic effects are completely removed (i.e., the functional model is good). In the GPS precise point positioning (PPP) the stochastic and functional models are not as complicated as in the differential GPS processing. We will assess the quality of the GPS Precise Point Positioning in this thesis by trying to define more realistic standard deviations for the station position estimates. To refine the functional model from systematic errors, we have 1) used the phase observations to prevent introducing any hardware bias to the observation equations, 2) corrected observations for all systematic effects with amplitudes of more than 1cm, 3) used undifferenced observations to prevent having complications (e.g. linearly related parameters) in the system of observation equations. To have a realistic covariance matrix for the observations we have incorporated the ephemeris uncertainties into the system of observation equations. Based on the above-mentioned issues a PPP processing method is designed and numerically tested on the real data of some of the International GNSS Service stations. The results confirm that undifferenced stochastic-related properties (e.g. degrees of freedom) can be reliable means to recognize the parameterization problem in differenced observation equations. These results also imply that incorporation of the satellite ephemeris uncertainties might improve the estimates of the station positions. The effect of troposphere on the GPS data is also focused in this thesis. Of particular importance is the parameterization problem of the wet troposphere in the observation equations.QC 20130218</p

Remarks on the quality of GPS precise point positioning using phase observations

GPS processing, like every processing method for geodetic applications, relies upon least-squares estimation. Quality measures must be defined to assure that the estimates are close to reality. These quality measures are reliable provided that, first, the covariance matrix of the observations (the stochastic model) is well defined and second, the systematic effects are completely removed (i.e., the functional model is good). In the GPS precise point positioning (PPP) the stochastic and functional models are not as complicated as in the differential GPS processing. We will assess the quality of the GPS Precise Point Positioning in this thesis. To refine the functional model from systematic errors, we have 1) used the phase observations to prevent introducing any hardware bias to the observation equations, 2) corrected observations for all systematic effects with amplitudes of more than 1cm, 3) used undifferenced observations to prevent having complications (e.g. linearly related parameters) in the system of observation equations. To have a realistic covariance matrix for the observations we have incorporated the ephemeris’ uncertainties into the system of observation equations. The above-mentioned technique is numerically tested on the real data of some of the International GNSS Service stations. The results confirm that undifferenced stochastic-related properties (e.g. degrees of freedom) can be reliable means to recognize the parameterization problem in differenced observation equations. These results also imply that incorporation of the satellite ephemeris uncertainties might improve the estimates of the station positions.QC 2012050

Developing a model for predicting the number of freight accidents involving death and injury Using Genetic Planning

Today, due to the importance of transportation in developing countries, addressing the issues related to transportation safety planning has also become increasingly important. One of the important issues in the field of safety planning is the synchronization of safety planning with the stages of transportation planning and predicting large-scale accidents is one of its components. The purpose of this research is to present a mathematical model for predicting the number of severe road traffic accidents along with transport planning and determine the most appropriate planning stage for building macro level accident prediction models. In this paper, by examining the factors affecting accidents, the macro model is presented using genetic programming method. For this purpose, data from the years 2011 to 2014 were used as baseline data and statistics from year 2015 were used to validate the model. Based on the data of each planning step, separate models were developed and after comparison between them, the model based on travel production variables was identified as the optimal model. The results show that among the data corresponding to the transport planning stages, the variables of the trip generation stage are the most appropriate data set for modelling of predicting road freight accidents

Solving the Direct and Inverse Geodetic Problems on the Ellipsoid by Numerical Integration

Taking advantage of numerical integration, we solve the direct and inverse geodetic problems on the ellipsoid. In general, the solutions are composed of a strict solution for the sphere plus a correction to the ellipsoid determined by numerical integration. Primarily the solutions are integrals along the geodesic with respect to the reduced latitude or azimuth, but these techniques either have problems when the integral passes a vertex (i.e., point with maximum/minimum latitude of the arc) or a singularity at the equator. These problems are eliminated when using Bessel's idea of integration along the geocentric angle of the great circle of an auxiliary sphere. Hence, this is the preferred method. The solutions are validated by some numerical comparisons to Vincenty's iterative formulas, showing agreements to within 2 x 10(-10) of geodesic length (or 3.1 mm) and 4 x 10(-5) as seconds of azimuth and position for baselines in the range of 19,000 km.QC 2012041

Reality measure of the published GPS satellite ephemeris uncertainties

The international GNSS service (IGS) started publishing the precise ephemeris files in the form of the standard products #3, version C (the sp3c files) in which the GPS satellite orbits and clocks and their uncertainties were available since 2004. Incorporating these uncertainties into the GPS observation equations results in a better stochastic model of the processing system. The reality of these uncertainties is questioned and studied in this paper. Precise point positioning (PPP) model, statistical tests and variance component estimation (VCE) techniques are employed for this study. The results confirm the efficiency of the proposed method in the assessment of reality of the published ephemeris uncertainties

Mantle viscosity derived from geoid and different land uplift data in Greenland

The Earth’s mass redistribution due to deglaciation and recent ice sheet melting causes changes in the Earth’s gravity field and vertical land motion in Greenland. The changes are because of ongoing mass redistribution and related elastic (on a short time scale) and viscoelastic (on time scales of a few thousands of years) responses. These signatures can be used to determine the mantle viscosity. In this study, we infer the mantle viscosity associated with the glacial isostatic adjustment (GIA) and long-wavelength geoid beneath the Greenland lithosphere. The viscosity is determined based on a spatio-spectral analysis of the Earth’s gravity field and the land uplift rate in order to find the GIA-related gravity field. We used and evaluated different land uplift data, i.e. the vertical land motions obtained by the Greenland Global Positioning System (GPS) Network (GNET), GRACE and Glacial Isostatic Adjustment (GIA) data. In addition, a  combined land uplift rate using the Kalman filtering technique is presented in this study. We extract the GIA-related gravity signals by filtering the other effects due to the deeper masses i.e. core-mantle (related to long-wavelengths) and topography (related to short-wavelengths). To do this, we applied correlation analysis to detect the best harmonic window. Finally, the mantle viscosity using the obtained GIA-related gravity field is estimated. Using different land uplift rates, one can obtain different GIA-related gravity fields. For example, different harmonic windows were obtained by employing different land uplift datasets, e.g. the truncated geoid model with a harmonic window between degrees 10 to 39 and 10 to 25 showed a maximum correlation with the GIA model ICE-6G (VM5a) and the combined land uplift rates, respectively. As shown in this study, the mantle viscosities of 1.6×1022 Pa s and 0.9×1022 Pa s for a depth of 200  to 650  km are obtained using ICE-6G (VM5a) model and the combined land uplift model, respectively, and the GIA-related gravity potential signal

Mantle Viscosity Derived From Geoid and Different Land Uplift Data in Greenland

The Earth's mass redistribution due to deglaciation and recent ice sheet melting causes changes in the Earth's gravity field and vertical land motion in Greenland. The changes are because of ongoing mass redistribution and related elastic (on a short time scale) and viscoelastic (on time scales of a few thousands of years) responses. These signatures can be used to determine the mantle viscosity. In this study, we infer the mantle viscosity associated with the glacial isostatic adjustment (GIA) and long-wavelength geoid beneath the Greenland lithosphere. The viscosity is determined based on a spatio-spectral analysis of the Earth's gravity field and the land uplift rate in order to find the GIA-related gravity field. We used different land uplift data, that is, the vertical land motions obtained by the Greenland Global Positioning System (GPS) Network (GNET), gravity recovery and climate experiment (GRACE) and glacial isostatic adjustment (GIA) data, and also combined them using the Kalman filtering technique. Using different land uplift rates, one can obtain different GIA-related gravity fields. As shown in this study, the mantle viscosities of 1.9 × 1022 Pa s and 7.8 × 1021 Pa s for a depth of 200–700 km are obtained using ICE-6G (VM5a) model and the combined land uplift model, respectively, and the GIA-related gravity potential signa