Showing papers in "Journal of Modern Transportation in 2016"

Autonomous vehicles: challenges, opportunities, and future implications for transportation policies

Abstract: This study investigates the challenges and opportunities pertaining to transportation policies that may arise as a result of emerging autonomous vehicle (AV) technologies. AV technologies can decrease the transportation cost and increase accessibility to low-income households and persons with mobility issues. This emerging technology also has far-reaching applications and implications beyond all current expectations. This paper provides a comprehensive review of the relevant literature and explores a broad spectrum of issues from safety to machine ethics. An indispensable part of a prospective AV development is communication over cars and infrastructure (connected vehicles). A major knowledge gap exists in AV technology with respect to routing behaviors. Connected-vehicle technology provides a great opportunity to implement an efficient and intelligent routing system. To this end, we propose a conceptual navigation model based on a fleet of AVs that are centrally dispatched over a network seeking system optimization. This study contributes to the literature on two fronts: (i) it attempts to shed light on future opportunities as well as possible hurdles associated with AV technology; and (ii) it conceptualizes a navigation model for the AV which leads to highly efficient traffic circulations.

A data mining approach to characterize road accident locations

Abstract: Data mining has been proven as a reliable technique to analyze road accidents and provide productive results. Most of the road accident data analysis use data mining techniques, focusing on identifying factors that affect the severity of an accident. However, any damage resulting from road accidents is always unacceptable in terms of health, property damage and other economic factors. Sometimes, it is found that road accident occurrences are more frequent at certain specific locations. The analysis of these locations can help in identifying certain road accident features that make a road accident to occur frequently in these locations. Association rule mining is one of the popular data mining techniques that identify the correlation in various attributes of road accident. In this paper, we first applied k-means algorithm to group the accident locations into three categories, high-frequency, moderate-frequency and low-frequency accident locations. k-means algorithm takes accident frequency count as a parameter to cluster the locations. Then we used association rule mining to characterize these locations. The rules revealed different factors associated with road accidents at different locations with varying accident frequencies. The association rules for high-frequency accident location disclosed that intersections on highways are more dangerous for every type of accidents. High-frequency accident locations mostly involved two-wheeler accidents at hilly regions. In moderate-frequency accident locations, colonies near local roads and intersection on highway roads are found dangerous for pedestrian hit accidents. Low-frequency accident locations are scattered throughout the district and the most of the accidents at these locations were not critical. Although the data set was limited to some selected attributes, our approach extracted some useful hidden information from the data which can be utilized to take some preventive efforts in these locations.

Driving skill classification in curve driving scenes using machine learning

Abstract: Driver support and infotainment systems can be adapted to the specific needs of individual drivers by assessing driver skill and state. In this paper, we present a machine learning approach to classifying the skill at maneuvering by drivers using both longitudinal and lateral controls in a vehicle. Conceptually, a model of drivers is constructed on the basis of sensor data related to the driving environment, the drivers’ behaviors, and the vehicles’ responses to the environment and behavior together. Once the model is built, the driving skills of an unknown driver can be classified automatically from the driving data. In this paper, we demonstrate the feasibility of using the proposed method to assess driving skill from the results of a driving simulator. We experiment with curve driving scenes, using both full curve and segmented curve scenarios. Six curves with different radii and angular changes were set up for the experiment. In the full curve driving scene, principal component analysis and a support vector machine-based method accurately classified drivers in 95.7 % of cases when using driving data about high- and low/average-skilled driver groups. In the cases with segmented curves, classification accuracy was 89 %.

Improvement of railway performance: a study of Swedish railway infrastructure

Abstract: The volume of rail traffic was increased by 5% from 2006 to 2010, in Sweden, due to increased goods and passenger traffic. This increased traffic, in turn, has led to a more rapid degradation of th ...

Overview and outlook on railway track stiffness measurement

Abstract: Stiffness is one of the basic performance parameters for railway track. The efficient and accurate stiffness measurement has been considered as the foundation for further development of railway engineering, and therefore has great theoretical and practical significance. Based on a summary of the connotation and measurement of track stiffness, the state of the art of measurement methods for track stiffness was analyzed systematically. The standstill measurement of track stiffness can be performed with the traditional jack-loading method, impact hammer method, FWD (falling weight deflectometer) method, and track loading vehicle method. Although these methods can be adopted in stiffness measurement for a section of railway track, they are not desirable owning to small range and low efficiency. In the recent 20 years, researchers have proposed many methods like unbalanced-loading laser displacement method, deflection basin deformation rate method, and eccentricity excitation method to continuously measure track stiffness; however, these methods have drawbacks like poor accuracy, low speed, and insufficient data analysis. In this work, the merits and demerits of these methods were summarized, and optimization suggestions were presented. Based on the wave transmission mechanism and principle of vibration energy harvesting, an overall conception on continuous measurement of stiffness and long-term stiffness monitoring for special sections was proposed.

Evolution of the electrical contact of dynamic pantograph–catenary system

Abstract: A good contact between the pantograph and catenary is critically important for the working reliability of electric trains, while the basic understanding on the electrical contact evolution during the pantograph–catenary system working is still ambiguous so far. In this paper, the evolution of electric contact was studied in respects of the contact resistance, temperature rise, and microstructure variation, based on a home-made pantograph–catenary simulation system. Pure carbon strips and copper alloy contact wires were used, and the experimental electrical current, sliding speed, and normal force were set as 80 A, 30 km/h, and 80 N, respectively. The contact resistance presented a fluctuation without obvious regularity, concentrating in the region of 25 and 50 mΩ. Temperature rise of the contact point experienced a fast increase at the first several minutes and finally reached a steady state. The surface damage of carbon trips in microstructure analysis revealed a complicated interaction of the sliding friction, joule heating, and arc erosion.

A multidimensional examination of performances of HSR (High-Speed Rail) systems

Abstract: This paper deals with a multidimensional examination of the infrastructural, technical/technological, operational, economic, social, and environmental performances of high-speed rail (HSR) systems, including their overview, analysis of some real-life cases, and limited (analytical) modeling. The infrastructural performances reflect design and geometrical characteristics of the HSR lines and stations. The technical/technological performances relate to the characteristics of rolling stock, i.e., high-speed trains, and supportive facilities and equipment, i.e., the power supply, signaling, and traffic control and management system(s). The operational performances include the capacity and productivity of HSR lines and rolling stock, and quality of services. The economic performances refer to the HSR systems’ costs, revenues, and their relationship. The social performances relate to the impacts of HSR systems on the society such as congestion, noise, and safety, and their externalities, and the effects in terms of contribution to the local and global/country social-economic development. Finally, the environmental performances of the HSR systems reflect their energy consumption and related emissions of green house gases, land use, and corresponding externalities.

Review of recent progress in studies on noise emanating from rail transit bridges

Abstract: In recent years, there has been rapid growth of Chinese rail transit networks. Many of these networks require elevated bridges. This results in a bridge-borne noise source, which occurs in addition to the main noise source (i.e., wheel–rail interactions). Bridge-borne noise is attracting increasing attention because of its low-frequency noise characteristics. This review paper first analyzes the space distribution, spectral characteristics, and sound pressure levels of noise radiated by all-concrete, steel–concrete composite, and all-steel bridges, mainly according to experimental studies. Second, this paper reviews existing theoretical prediction models of noise emanating from bridges: the semianalytical method, the Rayleigh integral method, the boundary element method, and statistical energy analysis. Several case studies are reviewed, and their results are discussed. Finally, according to the results of the current review, the main factors affecting bridge-borne noise are analyzed, several noise reduction measures are proposed for different types of bridges, and their effectiveness is demonstrated.

A technical review on persistent scatterer interferometry

Abstract: This article focuses on reviewing the technologies of persistent scatterer interferometry (PSI), which has been often used to monitor the deformation of Earth surface. Three critical steps in the implementation of PSI were introduced, i.e., (1) detection of persistent scatterer (PS), (2) construction of PS network, and (3) PSI modeling and solution. Finally, the main problems and outlooks on the PSI technique are discussed and given.

Injury severity analysis: comparison of multilevel logistic regression models and effects of collision data aggregation

Abstract: This paper describes an empirical study aiming at identifying the main differences between different logistic regression models and collision data aggregation methods that are commonly applied in road safety literature for modeling collision severity. In particular, the research compares three popular multilevel logistic models (i.e., sequential binary logit models, ordered logit models, and multinomial logit models) as well as three data aggregation methods (i.e., occupant based, vehicle based, and collision based). Six years of collision data (2001–2006) from 31 highway routes from across the province of Ontario, Canada were used for this analysis. It was found that a multilevel multinomial logit model has the best fit to the data than the other two models while the results obtained from occupant-based data are more reliable than those from vehicle- and collision-based data. More importantly, while generally consistent in terms of factors that were found to be significant between different models and data aggregation methods, the effect size of each factor differ substantially, which could have significant implications for evaluating the effects of different safety-related policies and countermeasures.

Derailment risk and dynamics of railway vehicles in curved tracks: Analysis of the effect of failed fasteners

Abstract: The effect of the fastener’s failure in a railway track on the dynamic forces produced in the wheel-rail contact is studied using the simulation software VAMPIRE to assess the derailment risk of two different vehicles in two curves with distinct characteristics. First, a 3D-FEM model of a real track is constructed, paying special attention to fasteners, and calibrated with displacement data obtained experimentally during a train passage. This numerical model is subsequently used to determine the track vertical and lateral stiffness. This study evidences that although the track can practically lose its lateral stiffness as a consequence of the failure of 7 consecutive fasteners, the vehicle stability would not be necessarily compromised in the flawed zone. Moreover, the results reveal that the uncompensated acceleration and the distance along which the fasteners are failed play an important role in the dynamic behavior of the vehicle-track system, influencing strongly the risk of derailment.

Safety evaluation for railway vehicles using an improved indirect measurement method of wheel–rail forces

Abstract: The wheel–rail force measurement is of great importance to the condition monitoring and safety evaluation of railway vehicles. In this paper, an improved indirect method for wheel–rail force measurement is proposed to evaluate the running safety of railway vehicles. In this method, the equilibrium equations of a suspended wheelset are derived and the wheel–rail forces are then be obtained from measured suspension and inertia forces. This indirect method avoids structural modifications to the wheelset and is applicable to the long-term operation of railway vehicles. As the wheel–rail lateral forces at two sides of the wheelset are difficult to separate, a new derailment criterion by combined use of wheelset derailment coefficient and wheel unloading ratio is proposed. To illustrate its effectiveness, the indirect method is applied to safety evaluation of railway vehicles in different scenarios, such as the cross wind safety of a high-speed train and the safety of a metro vehicle with hunting motions. Then, the feasibility of using this method to identify wheel–rail forces for low-floor light rail vehicles with resilient wheels is discussed. The values identified by this method is compared with that by Simpack simulation for the same low-floor vehicle, which shows a good coincidence between them in the time domain of the wheelset lateral force and the wheel–rail vertical force. In addition, use of the method to determine the high-frequency wheel–rail interaction forces reveals that it is possible to identify the high-frequency wheel–rail forces through the accelerations on the axle box.

Bluetooth as a traffic sensor for stream travel time estimation under Bogazici Bosporus conditions in Turkey

Abstract: Travel time estimation is an integral part of Intelligent Transportation Systems, and has been an important component in traffic management and operations for many years. Travel time, being spatial in nature, requires spatial sensors to measure it accurately. Bluetooth is emerging as a promising technology for the direct measurement of travel time, and is reported in a few studies from homogenous traffic conditions. At the same time, there have been no studies on the applicability of Bluetooth for travel time estimation in heterogeneous traffic seen in Istanbul and even that Turkey. Bluetooth data collected from a busy urban road in Istanbul city have been analyzed and the penetration rate was found to be about 5 %. Two wheelers and light motor vehicles have been detected using the Bluetooth sensor and the data have been extrapolated to estimate travel times of other classes of vehicles. The study developed linear relationships between speeds of different classes of vehicles through weighted linear regression methods and were used for the estimation of stream travel time. The results obtained were promising and show that Bluetooth is a cost-effective technology for estimation of travel time for heterogeneous traffic conditions.

Comparative study of China and USA public private partnerships in public transportation

Abstract: As an effective alternative approach to provide goods and services for public infrastructure, the Public Private Partnership (PPP) has been studied extensively over the past few decades. On a global scale, China and the United States have developed cooperation on PPP projects in various areas. To perform a comparative study, this paper analyzes how PPP projects work in both countries for public transportation. The basic features, types, and phases of PPPs in public transportation are introduced first, followed by a thorough discussion on their advantages and challenges. This paper adopts a case study method to analyze the achievements and problems of PPP projects in both countries and then proposes important findings and suggestions for future research.

Impacts of cell phone use on driving safety and drivers’ perception of risk

Abstract: In this study, the factors influencing phone-related driving safety and drivers’ perceptions of cell phone usage were analyzed. A representative sample of more than 500 licensed drivers in Texas who own a cell phone was interviewed based on a well-design questionnaire. Logistic regression model showed that the impact of using cell phone on driving safety varies depending on the characteristics of drivers, such as gender, age, driving experience, and use intensity. Additionally, the results indicated that the strong determinants of phone-related hazard are different from that of phone-related accidents. Regarding the drivers’ perception of cell phone usage, there are two key findings. First, there is no explicit belief among the drivers about whether cell phone usage impairs driving safety regardless of the drivers’ age, gender, driving education experience etc. Second, most of drivers have not realized that cell phone use while driving would increase their perception reaction time. Based on the analysis of these results, implications of cell phone use on driving safety along with some safety countermeasures, such as selective bans and non-cell phone zones, are discussed in the paper.

Key factors contributing to crash severity at highway-rail grade crossings

Abstract: The purpose of this paper is to develop and compare the preferred multinomial logit (MNL) and ordered logit (ORL) model in identifying factors that are important in making an injury severity difference and exploring the impact of such explanatory variables on three different severity levels of vehicle-related crashes at highway-rail grade crossings (HRGCs) in the United States. Vehicle-rail crash data on USDOT highway-rail crossing inventory and public crossing sites from 2005 to 2012 are used in this study. Preferred MNL and ORL models are developed and marginal effects are also calculated and compared. A majority of the variables have shown similar effects on the probability of the three different severity levels in both models. In addition, based on the Akaike information criterion, it is found that the MNL model is better than the ORL model in predicting the vehicle crash severity levels on HRGCs in this study. Therefore, the researchers recommend the use of MNL model in predicting severity levels of vehicle-rail crashes on HRGCs.

Analysis of occupation time of vehicles at urban unsignalized intersections in non-lane-based mixed traffic conditions

Abstract: In India, traffic flow on roads is highly mixed in nature with wide variations in the static and dynamic characteristics of vehicles. At unsignalized intersections, vehicles generally do not follow lane discipline and ignore the rules of priority. Drivers generally become more aggressive and tend to cross the uncontrolled intersections without considering the conflicting traffic. All these conditions cause a very complex traffic situation at unsignalized intersections which have a great impact on the capacity and performance of traffic intersections. A new method called additive conflict flow (ACF) method is suitable to determine the capacity of unsignalized intersections in non-lane-based mixed traffic conditions as prevailing in India. Occupation time is the key parameter for ACF method, which is defined as the time spent by a vehicle in the conflict area at the intersection. Data for this study were collected at two three-legged unsignalized intersections (one is uncontrolled and other one is semicontrolled) in Mangalore city, India using video-graphic technique during peak periods on three consecutive week days. The occupation time of vehicles at these intersections were studied and compared. The data on conflicting traffic volume and occupation time by each subject vehicle at the conflict area were extracted from the videos using image processing software. The subject vehicles were divided into three categories: two wheelers, cars, and auto-rickshaws. Mathematical relationships were developed to relate the occupation time of different categories of vehicles with the conflicting flow of vehicles for various movements at both the intersections. It was found that occupation time increases with the increasing conflicting traffic and observed to be higher at the uncontrolled intersection compared to the semicontrolled intersection. The segregated turning movements and the presence of mini roundabout at the semicontrolled intersection reduces the conflicts of vehicular movements, which ultimately reduces the occupation time. The proposed methodology will be useful to determine the occupation time for various movements at unsignalized intersections. The models developed in the study can be used by practitioners and traffic engineers to estimate the capacity of unsignalized intersections in non-lane-based discipline and mixed traffic conditions.

Industrial frequency single-phase AC traction power supply system for urban rail transit and its key technologies

Abstract: To avoid stray current and maintain the benefit of no phase-split in the DC traction power supply system, an AC traction power supply system was proposed for the urban public transport such as metro and light rail transit. The proposed system consists of a main substation (MSS) and cable traction network (CTN). The MSS includes a single-phase main traction transformer and a negative-sequence compensation device, while the CTN includes double-core cables, traction transformers, overhead catenary system, rails, etc. Several key techniques for the proposed system were put forward and discussed, which can be summarized as (1) the power supply principle, equivalent circuit and transmission ability of the CTN, the cable-catenary matching technique, and the selection of catenary voltage level; (2) the segmentation technology and status identification method for traction power supply network, distributed and centralized protection schemes, etc.; (3) a power supply scheme for single-line MSS and a power supply scheme of MSS shared by two or more lines. The proposed industrial frequency single-phase AC traction power supply system shows an excellent technical performance, good economy, and high reliability, hence provides a new alternative for metro and urban rail transit power supply systems.

Mechanism and effects of snow accumulations and controls by lightweight snow fences

Abstract: This paper investigates the snowdrifts caused by lightweight fences along the lines on the flatland through the computational fluid dynamics method. The characteristic ambient flows around the solid fences and the porous fences with varied heights and bottom wind gaps are simulated in the numerical model, and the working mechanism of “interception” and “scouring” of the lightweight fences are analyzed. Based on the friction velocities near the ground, two sets of criteria are proposed to evaluate the deposition and erosion effects of different fences. According to flow separation and reattachment, the simplified relationships between the most likely positions for snow accumulations and fence parameters are developed. The study indicates that the capabilities for snow interception by the solid fence without wind gap and the distance from which to the second snow coverage center both increase with the fence height. Furthermore, it is found that the scouring range for snow surface increases significantly with the size of wind gap, and the snow accumulation rate on the leeward side decreases with the increasing fence porosity.

Residential relocation in response to light rail transit investment: case study of the Hudson–Bergen Light Rail system

Abstract: It is widely acknowledged that the improved accessibility enabled by investment in public transport services can, under favorable market conditions, impact the local real estate market within the zone of influence of the service’s stations. The motivation for this study is to establish the nature of two such impacts, specifically the spatial and socio-economic patterns of residential relocations that are driven by the new light rail transit (LRT) service. Using empirical data (n = 1,023) from the Hudson–Bergen Light Rail system in New Jersey (US), we report findings regarding the impacts of the introduction of the new LRT service. We investigate two linked dimensions; the first is the distinctive socio-economic profile of LRT passengers who self-report having relocated to the new transit corridor due, at least in part, to the new transit service. The second is their proximity (following their residential relocation) to the new LRT line’s stations. We present a novel analysis that accounts for endogeneity between these two dimensions of residential relocation. Of light rail passengers who engaged in a residential relocation in the 5 years prior to the survey, two-thirds (69 %) indicate that proximity to the light rail service was a ‘somewhat’ or ‘very’ important consideration. Via the multivariate analysis, we demonstrate that small household size, low income, youth (as opposed to older age), and low car ownership are each positively linked, ceteris paribus, with having engaged in a residential relocation motivated by the new transit service. Finally, higher household income is found to be associated with distance (after relocation) to the nearest transit station, which is consistent with bid-rent theory.

Verifying the accuracy of interlocking tables for railway signalling systems using abstract state machines

Abstract: Railway transportation system is a critical sector where design methods and techniques are defined by international standards in order to reduce possible risks to an acceptable minimum level CENELEC 50128 strongly recommends the utilization of finite state machines during system modelling stage and formal proof methods during the verification and testing stages of control algorithms Due to the high importance of interlocking table at the design state of a signalization system, the modelling and verification of interlocking tables are examined in this work For this purpose, abstract state machines are used as a modelling tool The developed models have been performed in a generalized structure such that the model control can be done automatically for the interlocking systems In this study, NuSMV is used at the verification state Also, the consistency of the developed models has been supervised through fault injection The developed models and software components are applied on a real railway station operated by Metro Istanbul Co

Micro-simulation model of two-lane freeway vehicles for obtaining traffic flow characteristics including safety condition

Abstract: Unidirectional two-lane freeway is a typical and the simplest form of freeway. The traffic flow characteristics including safety condition on two-lane freeway is of great significance in planning, design, and management of a freeway. Many previous traffic flow models are able to figure out flow characteristics such as speed, density, delay, and so forth. These models, however, have great difficulty in reflecting safety condition of vehicles. Besides, for the cellular automation, one of the most widely used microscopic traffic simulation models, its discreteness in both time and space can possibly cause inaccuracy or big errors in simulation results. In this paper, a micro-simulation model of two-lane freeway vehicles is proposed to evaluate characteristics of traffic flow, including safety condition. The model is also discrete in time but continuous in space, and it divides drivers into several groups on the basis of their preferences for overtaking, which makes the simulation more aligned with real situations. Partial test is conducted in this study and results of delay, speed, volume, and density indicate the preliminary validity of our model, based on which the proposed safety coefficient evaluates safety condition under different flow levels. It is found that the results of this evaluation coincide with daily experience of drivers, providing ground for effectiveness of the safety coefficient.

A new lever-type variable friction damper for freight bogies used in heavy haul railway

Abstract: To overcome defects caused by the complex structure and unstable damping performance of the wedge-type damper, a new lever-type friction damper has been developed for use in freight bogies; the design allows the advantages of traditional three-piece bogies to be retained. A detailed description of the structure and mechanism of the lever-type damper is provided, followed by a stress analysis using the finite element method. Dynamic performance characteristics of the lever-type damper and the wedge-type damper are compared in terms of the nonlinear critical speed, riding index, and curve negotiation. The results indicate that the maximum stress of the lever remains below its yield limit. The lever-type car has higher running performance reliability, and achieves similar nonlinear critical speed, riding index, and curve negotiation when compared with the wedge-type car.

Distribution characteristics and influencing factors of the frequency-domain response of a vehicle–track vertical coupled system

Abstract: Employing theory on vehicle–track coupled dynamics, the equation of motion of a vehicle–track vertical coupled system was established by combining frequency analysis and symplectic mathematics. The frequency response of the vehicle–track vertical coupled system was calculated under the excitation of the German low-interference spectrum, and the effects of the vehicle speed, vehicle suspension parameters, and track support parameters on the frequency response of the coupled system were studied. Results show that, under the excitation of the German low-interference spectrum, the vertical vibration of the car body is mainly concentrated in the low-frequency band, while that of the bogie has a wide frequency distribution, being strong from several Hertz to dozens of Hertz. The vertical vibrations of the wheel–rail force, wheelset, and track structure mainly occur at a frequency of dozens of Hertz. In general, the vertical vibration of the vehicle–track coupled system increases with vehicle speed, and the vertical vibrations of the car body and bogie obviously shift to higher frequency. Increasing the vehicle suspension stiffness increases the low-frequency vibrations of the vehicle system and track structure. With an increase in vehicle suspension damping, the low-frequency vibrations of the car body and bogie and the vibrations of the wheel–rail vertical force and track structure decrease at 50–80 Hz, while the mid-frequency and high-frequency vibrations of the car body and bogie increase. Similarly, an increase in track stiffness amplifies the vertical vibrations of the wheel–rail force and track structure, while an increase in track damping effectively reduces the vertical vibrations of the wheel–rail vertical force and track structure.

Investigation into rail corrugation in high-speed railway tracks from the viewpoint of the frictional self-excited vibration of a wheel–rail system

Abstract: A finite element vibration model of a multiple wheel–rail system which consists of four wheels, one rail, and a series of sleepers is established to address the problem of rail corrugation in high-speed tracks. In the model, the creep forces between the wheels and rail are considered to be saturated and equal to the normal contact forces times the friction coefficient. The oscillation of the rail is coupled with that of wheels in the action of the saturated creep forces. When the coupling is strong, self-excited oscillation of the wheel–rail system occurs. The self-excited vibration propensity of the model is analyzed using the complex eigenvalue method. Results show that there are strong propensities of unstable self-excited vibrations whose frequencies are less than 1,200 Hz under some conditions. Preventing wheels from slipping on rails is an effective method for suppressing rail corrugation in high-speed tracks.

Analysis of the stress intensity factor of welded joints under prior corrosion and complex stress fields

Abstract: Taking cruciform welded joints under different corrosion degrees, together with 45° inclined angle and full penetration load-carrying fillet, as the research object, the stress intensity factor of a quarter-circular corner crack of welded joints is calculated based on FRANC3D with ABAQUS. Effects of different corrosion pit sizes, crack aspect ratios, and crack depths on stress intensity factor are analyzed. The results show that pit depth plays a major role in stress intensity factor, while the effect of pit radius is relatively small. The cracking modes of the surface and the deepest point are mode I, and mixed modes I and II, respectively. Effects of pit depths, crack aspect ratios, and crack depths on the stress intensity factor at the surface point are greater than at the deepest point.

A comparative study of automotive trip characteristics between older drivers and others among densely inhabited district and other areas

Abstract: This paper examines older driver’s automotive trip (abbreviation: trip) characteristics which include trip frequency, trip length, destination distribution, and non-home-based (NHB) trips. A two-month experiment of 108 participants was carried out to collect GPS tracking data in Aichi Prefecture, Japan. To identify the effect of living area, a comparative analysis between older drivers and others is conducted in densely inhabited district (DID, i.e., urban) and other areas (non-DID, i.e., suburban, rural, etc), separately. The present study found that there was no significant difference between the trip characteristics of older drivers and others who were living in DID. Thus, we suggest that the education of safety driving and the recommendation of public transportation should be given to DID-living older drivers. However, the results of non-DID reflected that older drivers’ trip frequency, trip length, destination, and NHB trips rate were shorter and lower than others’. This implies that electric vehicles may be suitable for promotion among older drivers in suburban and rural area. Furthermore, the regression analysis confirmed that “older driver” was a significant independent variable on trip frequency, trip length, and NHB trips, and there were interaction effects between “older driver” and “living areas” on all trip characteristics.

Calibration of a rule-based intelligent network simulation model

Abstract: This paper is focused on calibration of an intelligent network simulation model (INSIM) with real-life transportation network to analyse the INSIM’s feasibility in simulating commuters’ travel choice behaviour under the influence of real-time integrated multimodal traveller information (IMTI). A transportation network model for the central and western areas of Singapore was simulated in PARAMICS and integrated with INSIM expert system by means of an application programming interface to form the INSIM. Upon calibration, INSIM was able to realistically present complicated scenarios in which real-time IMTI was provided to commuters and the network performance measures being recorded.

Simplified full-depth precast concrete deck panel systems for accelerated bridge construction

Abstract: A simplified full-depth precast concrete deck panel system for accelerating bridge construction (ABC) is introduced and a finite element analysis (FEA) is conducted to investigate the static and dynamic responses of this conceptual deck system. The FEA results are compared to those of the traditional full-depth precast concrete deck panel system. The comparison results show that the mechanical behavior of the new deck system is different from that of the traditional deck system. The concrete decks in the new system act as two-way slabs, instead of the one-way slab in the traditional system. Meanwhile, the connections in both the longitudinal and transverse directions may need to accommodate the negative moments. Compared to those in the traditional system, the longitudinal nominal stress at middle span increases a lot in the new deck system and the effective flange width varies significantly. In addition, the dynamic results show that the impact factor is influenced by the spacing of connections. Finally, some design concerns of the new deck system are proposed.