Showing papers in "International journal of transportation science and technology in 2016"

Unmanned Aerial Aircraft Systems for Transportation Engineering: Current Practice and Future Challenges

Abstract: Acquiring and processing video streams from static cameras has been proposed as one of the most efficient tools for visualizing and gathering traffic information. With the latest advances in technology and visual media, combined with the increased needs in dealing with congestion more effectively and directly, the use of Unmanned Aerial Aircraft Systems (UAS) has emerged in the field of traffic engineering. In this paper, we review studies and applications that incorporate UAS in transportation research and practice with the aim to set the grounds from the proper understanding and implementation of UAS related surveillance systems in transportation and traffic engineering. The studies reviewed are categorized in different transportation engineering areas. Additional significant applications from other research fields are also referenced to identify other promising applications. Finally, issues and emerging challenges in both a conceptual and methodological level are revealed and discussed.

Unmanned Aircraft System traffic management: Concept of operation and system architecture

Abstract: Within the past few years, civilian demand for small unmanned aircraft systems (sUAS), commonly referred to as drones, has skyrocketed. The passage of the Federal Aviation Administration (FAA) Modernization and Reform Act in 2012 acknowledged this fact, and has since prompted expedited research and development for civilian sUAS. As proposed at a recent National Aeronautics and Space Administration (NASA) Convention, central to the safe and efficient operations of sUAS will be an unmanned aircraft system traffic management (UTM) system. Such a UTM system will borrow fundamental ideas from large-scale air-traffic control, albeit with several key differences that provide for sUAS which vary in method of control, maneuverability, function, range, and operational constraints. Ultimately, an expansion of UTM infrastructure, a decentralization of governing authority over sUAS operations, and the establishment of a web-interface for pilots to submit flight plans and access crucial data will allow for sUAS operations to shift from being a science-fiction gimmick to an element of daily life. The major objectives of this paper are to: (1) define what a UTM system is; (2) review current UTM practice from industry partners; (3) describe how sUAS pilots would use a typical UTM system, and who has authority over UTM; and (4) determine what physical architecture is required in a UTM system which handles a large variety of sUAS.

Evaluating the Accuracy of Vehicle Tracking Data Obtained from Unmanned Aerial Vehicles

Abstract: This paper presents a methodology for tracking moving vehicles that integrates Unmanned Aerial Vehicles with video processing techniques. The authors investigated the usefulness of Unmanned Aerial Vehicles to capture reliable individual vehicle data by using GPS technology as a benchmark. A video processing algorithm for vehicles trajectory acquisition is introduced. The algorithm is based on OpenCV libraries. In order to assess the accuracy of the proposed video processing algorithm an instrumented vehicle was equipped with a high precision GPS. The video capture experiments were performed in two case studies. From the field, about 24,000 positioning data were acquired for the analysis. The results of these experiments highlight the versatility of the Unmanned Aerial Vehicles technology combined with video processing technique in monitoring real traffic data.

Dynamic UAV-based traffic monitoring under uncertainty as a stochastic arc-inventory routing policy

Abstract: Given the rapid advances in unmanned aerial vehicles, or drones, and increasing need to monitor at a city level, one of the current research gaps is how to systematically deploy drones over multiple periods. We propose a real-time data-driven approach: we formulate the first deterministic arc-inventory routing problem and derive its stochastic dynamic policy. The policy is expected to be of greatest value in scenarios where uncertainty is highest and costliest, such as city monitoring during major events. The Bellman equation for an approximation of the proposed inventory routing policy is formulated as a selective vehicle routing problem. We propose an approximate dynamic programming algorithm based on Least Squares Monte Carlo simulation to find that policy. The algorithm has been modified so that the least squares dependent variable is defined to be the “expected stock out cost upon the next replenishment”. The new algorithm is tested on 30 simulated instances of real time trajectories over 5 time periods of the selective vehicle routing problem to evaluate the proposed policy and algorithm. Computational results on the selected instances show that the algorithm on average outperforms the myopic policy by 23–28%, depending on the parametric design. Further tests are conducted on classic benchmark arc routing problem instances. The 11-link instance gdb19 (Golden et al., 1983) is expanded into a sequential 15-period stochastic dynamic example and used to demonstrate why a naive static multi-period deployment plan would not be effective in real networks.

Truck acceleration behavior study and acceleration lane length recommendations for metered on-ramps

Abstract: This paper investigated the actual truck acceleration capability at metered on-ramps. Truck acceleration performance data were collected through a video-based data collection method. A piecewise constant acceleration model was employed to capture truck acceleration characteristics. It was found that the existing acceleration length will affect truck drivers’ acceleration behavior. At the taper type ramp that has limited acceleration distance, acceleration profile indicated a decreasing trend with distance. While for the ramp with an auxiliary lane that has sufficient acceleration distance, it was found that the acceleration behavior is to have a high acceleration rate in the beginning, then acceleration rate decrease with speed increase, and high acceleration rate again as drivers approach the merging area. Field data show that the truck acceleration performance data documented in the ITE’s (Institute of Transportation Engineers) “ Traffic Engineering Handbook ” are much lower than the field collected data. Also, based on the regression analysis of speed versus distance profiles, it was found that the AASHTO’s (American Association of State Highway and Transportation Officials) Green Book acceleration length design guidance is insufficient to accommodate trucks at metered on-ramps. The required acceleration lengths for medium and heavy trucks are approximately 1.3 and 1.6 times of the Green Book design guideline, respectively.

A video-based approach to calibrating car-following parameters in VISSIM for urban traffic

Abstract: Microscopic simulation models need to be calibrated to represent realistic local traffic conditions. Traditional calibration methods are conducted by searching for the model parameter set that minimizes the discrepancies of certain macroscopic metrics between simulation results and field observations. However, this process could easily lead to inappropriate selection of calibration parameters and thus erroneous simulation results. This paper proposes a video-based approach to incorporate direct measurements of car-following parameters into the process of VISSIM model calibration. The proposed method applies automated video processing techniques to extract vehicle trajectory data and utilizes the trajectory data to determine values of certain car-following parameters in VISSIM. This paper first describes the calibration procedure step by step, and then applies the method to a case study of simulating traffic at a signalized intersection in VISSIM. From the field-collected video footage, trajectories of 1229 through-movement vehicles were extracted and analyzed to calibrate three car-following parameters regarding desired speed, desired acceleration, and safe following distance, respectively. The case study demonstrates the advantages and feasibility of the proposed approach.

Evaluating the performance of sustainable perpetual pavements using recycled asphalt pavement in China

Abstract: The vast highways network in China is moving from the phase of construction to the phase of maintenance, and with the introduction of new technique of perpetual pavement in last decade, it is necessary to consider recycling as one of the promising solutions for rehabilitation of old asphalt concrete pavement and ultimately to convert them into perpetual pavements. The aim is to reuse the existing pavement materials for several reasons, mainly to preserve natural resources such as aggregates, and to satisfy economic requirements by reducing the cost of highway construction and rehabilitation. A detailed testing program has been carried out on recycled asphalt pavements materials (RAP) to evaluate their mechanical and structural characteristics to be used for the construction and rehabilitation of road pavements. Different types of RAP mixes have been stabilized by Portland cement to find the most suitable one from the point of view of design, construction, economy and environment. The analysis of life cycle costs has been carried out using system analysis and management of pavement program (SAMP5). The analysis of life cycle costs showed that the use of Portland cements with small percentages improves the structural characteristics of recycled asphalt materials to be used as stabilized base pavement layers for new or rehabilitated old road pavements and also for the construction and rehabilitation of perpetual pavements. A large amount of savings in construction and rehabilitation cost has been achieved by the use of stabilized RAP materials in addition to important contributions to the environment and preserving of natural resources.

Towards an index of city readiness for cycling

Abstract: After decades of overdependence on motorized means of transport, and in acknowledgement of major environmental challenges, most of the world’s cities are recognizing the importance of adopting non-motorized means of transport to enhance their quality of life. Local authorities are interested in providing facilities that enable city residents to efficiently traverse the urban fabric. Cycling, as an important non-motorized mode of transport, is considered to be an efficient alternative to motor vehicles. Establishing safe and convenient cycle routes has become one of the main development tasks in contemporary cities. Indeed, converting today’s traditional cities into bicycle-friendly ones is considered to be one of the principal goals of development plans. This paper addresses the urban readiness of cities to be bicycle-friendly. It focuses on the socioeconomic and urban characteristics that have to be present in a city for cycling to be adopted as a primary mode of transport. Through statistical analysis of 20 bicycle-friendly cities, the paper identifies the main requirements for urban cycling. Finally, it evaluates the readiness of Egyptian cities to become bicycle-friendly.

Information synthesis and preliminary case study for life cycle assessment of reflective coatings for cool pavements

Abstract: This paper synthesizes existing available information and knowledge to enhance the understanding of the environmental impact of material production and construction of pavement reflective coatings. This work was performed through a literature survey of current technologies and products. Discussed in the paper are the classification, components, production method, typical albedo values and durability, application scope and rate, application method, and a preliminary partial assessment of the environmental impacts of pavement reflective coatings. The preliminary case study shows that compared to HMA and PCC overlays and even slurry seals, reflective coatings could have lower environmental impacts depending on their durability. However, unlike overlays, reflective coatings do not improve the surface smoothness and ride quality and therefore do not improve fuel consumption and user comfort during the use phase, which was not included in this preliminary LCA case study. The reflective coatings and slurry seal also do not improve structural capacity of the pavement.

Demand-responsive public transportation re-scheduling for adjusting to the joint leisure activity demand

Abstract: Fixed daily trips such as trips to work/school have fixed departure/arrival times and destination points. The recurrent nature of fixed activities facilitates individuals on making more well-informed decisions about the transport mode selection. On the contrary, selecting a transportation mode for non-recurrent leisure trips, which can account for up to 60% of trips in some cities (Transport for London, 2014), is a more complex task due to the fact that individuals have little knowledge about the alternative modal options. In this paper, we try to improve the operations of demand-responsive public transportation systems by increasing their service quality and their ridership related to joint-leisure-trips via timetable rescheduling. First, we model the public transport service re-scheduling problem considering operational regulations and the quality of service. Then, a sequential heuristic method is introduced for re-scheduling the timetables of demand-responsive public transport modes in near-real time and accommodating the joint leisure activity demand without deteriorating the quality of service. The public transport re-scheduling for increasing the joint leisure activity ridership was tested in a case study using user-generated data from social media in Stockholm and the General Transit Feed Specification (GTFS) data from Sweden focusing especially on central bus lines 1 and 4.

Quantifying the impact of road capacity loss on urban electrified transportation networks: An optimization based approach

Abstract: The proliferation of electric vehicles and commercialization of public charging facilities have inspired the emerging trend of transportation electrification, which creates an urgent demand for systematic methodologies to analyze the performance of electrified transportation networks (ETNs) while taking the interdependency across the transportation network and the power distribution network into account. This paper introduces a comprehensive mathematical formulation of the ETN from a system-level perspective, in which the steady-state distribution of the traffic flow is described by Wardrop user equilibrium, while the operating status of the power grid is characterized by a linearized branch power flow model. Moreover, this paper investigates the impact of road capacity degradation on the transportation network, which is quantified by the total vehicle travel time, as well as the power distribution network, which is quantified by the operating cost. The former gives rise to a nonlinear programming problem with complementarity constraints (NPCC), which is reformulated as a mixed integer linear program, thereby the global optimal solution can be found with moderate computational effort. The latter yields a max–min NPCC, which is transformed into an equivalent single-level NPCC; thus a commercial nonlinear solver is applicable to find a local solution. A derivative-free searching algorithm which relies on convex optimization is also suggested. Numerical case studies on a test system demonstrate the necessity of considering the intrinsic interdependency of the transportation and electricity infrastructures in designing and operating the ETN.

On accuracy of position estimation from aerial imagery captured by low-flying UAVs

Abstract: The application of low-flying Unmanned Aerial Vehicles (UAVs) for traffic monitoring and surveillance requires an estimation of position measurement accuracy of monitored objects. In this work we aim to analyse and provide insight into the accuracy of position estimation of objects based on aerial imagery captured by low flying UAV for the purpose of traffic monitoring. The analysis is focused on data gathered by a low-cost action camera mounted on a multicopter UAV flying above a planar scene. We assume a simple, straightforward method of position estimation of object based on homography mapping between two 2D planes derived from the position of images of landmarks – objects with known real world position. We assume errors caused by inaccuracy of the following values: the landmarks’ real world position, the landmarks’ and target’s real world elevation, and the captured image positions of both the landmarks and the target. Additionally, a geometric deformation of captured frame caused by imperfect camera lenses is considered. The paper further analyses the effect of varying magnitude of errors, camera position, incidence angle and both the landmarks’ and the target’s positions in the scene or captured frame, and compares the results with real world experiments. The results can be used to estimate the feasibility and applicability of certain solutions to object position estimation. The tool for the calculation of the accuracy of position estimation and locating the most suitable camera pose for a given setup is provided.

Linkage between passenger demand and surrounding land-use patterns at urban rail transit stations: A canonical correlation analysis method and case study in Chongqing

Abstract: This paper employs a canonical correlation analysis method to quantify the linkage between urban rail transit station demand and the surrounding land-use patterns. It is used to identify key land use variables by evaluating their degrees of contribution to the rail transit station demand. A full month of IC card data and detailed regulatory land use plan from Chongqing, China are collected for model development and validation. The proposed model contributes to offering the capability of targeting key land use patterns and associating them with rail transit station boarding and alighting demand simultaneously. The proposed model can reveal underlying rules between rail transit station demand and land use variables and can be used to evaluate the Transit Oriented Development (TOD) plans to improve land use and transit operational efficiency.

Understanding social media program usage in public transit agencies

Abstract: Social media has been gaining prominence in public transit agencies in their communication strategies and daily management. This study aims to better understand recent trends in social media usage in public transit agencies, to examine which agencies use what kind of social media programs for what purposes, and how they measure their programs. A survey was conducted of the top transit agencies in the nation, and results are examined through descriptive statistical analysis, correlation analysis and regression modeling. We found that while most agencies still lack clearly-defined goals and performance metrics to guide their social media development, many are increasing their social media capacity with more structural components. Public transit service usage and the level of transit service provision are the most significant determinants of agencies’ social media programming and resource investments. In contrast, the measurement of social media usage and outcomes is more significantly related to city attributes and demographic characteristics. We anticipate an increase in the usage of social media to convey transit related stories and livability benefits, such as environmental sensitivity or safety improvements, as these programs expand. Public transit agencies’ commitment to measuring social media outcomes underscores the future research need to develop best practices for measuring the impacts and performance of social media communications and investments.

Optimizing scheduling of long-term highway work zone projects

Abstract: The impacts of work zone activities can be summarized into the following types: safety impact (on both motorists and workers), mobility impact, economic considerations, environmental concerns, user cost as well as contractor’s maintenance cost. Various interest subjects may focus on different aspects of the six areas identified above. In this study, the impacts of scheduling long-term work zone activities are analyzed from the perspective of traffic agencies and jurisdictions. A bi-level genetic algorithm (GA)-based optimization model is formulated to determine the optimal starting date of each work zone project. The upper-level subprogram minimizes the total travel time over the entire planning horizon, while the lower-level subprogram is a user equilibrium (UE) problem where all users try to find the route that minimizes their own travel time. The demand, and the number of work zones as well as their durations are assumed to be fixed and given a priori. The proposed GA model is applied to the Sioux Falls network, which has 76 links and 24 origin–destination (O–D) pairs. The results of the numerical example indicate that the proposed model can effectively identify the near-optimal solution of the long-term work zone scheduling problem.

Methodology for estimating capacity and vehicle delays at unsignalized multimodal intersections

Abstract: An uncontrolled intersection is one where neither traffic signs nor lights, are used to guide the traffic through the intersection, but instead the drivers decide on the right of way based on some standard priority rules. This paper establishes a methodology to systematically evaluate the expected average delays at multi-modal uncontrolled intersections. The methodology considers the demand values of different traffic streams, along with the priority and direction of each stream to determine the capacity available for each. Using this capacity and the formula for delay adapted from the highway capacity manual, the average delay for each vehicle stream can be determined. The methodology is tested using data collected at five locations in Zurich, Switzerland. The results show that the methodology can predict the delay of different vehicle streams to within 4 s/veh, and also can identify the streams for which large delays would be expected.

Modeling cooperation and powered-two wheelers short-term strategic decisions during overtaking in urban arterials

Abstract: A difference between Powered Two Wheelers (PTW) drivers’ behavior and other drivers’ behavior in urban arterials is the frequency of overtaking. The present paper focuses on PTW overtaking and models the specific behavior using concepts of Game Theory. Both the PTW driver and the lead vehicle’s driver are assumed rational decision-makers that develop strategies, trying to maximize their payoffs. These strategies may be cooperative or not with respect to the distances and safety gaps and other behavioral aspects. The payoff function is formulated based on a novel latent statistically determined driving indicator, which quantifies both the driving risk and comfort. The proposed model is evaluated using trajectory data from video recordings on an urban arterial. Results show that both drivers have maximized gains by following a cooperative strategy. Findings also reveal that the successful overtaking rate is higher, when the PTW driver is non-cooperative, whereas lower overtaking rates occur, when the driver of the lead vehicle is non-cooperative. Finally, the concepts of Dominant Strategies, bounded rationality and the construction of the optimum payoff function are further discussed.

Analysis of factors temporarily impacting traffic sign readability

Abstract: Traffic sign readability can be affected by the existence of dirt on traffic sign faces However, among damaged signs, dirty traffic signs are unique since their damage is not permanent and they just can be cleaned instead of replaced This study aimed to identify the most important factors contributing to traffic sign dirt To do so, a large number of traffic signs in Utah were measured by deploying a vehicle instrumented with mobile LiDAR imaging and digital photolog technologies Each individual daytime digital image was inspected for dirt Location and climate observations obtained from official sources were compiled using ArcGIS throughout the process To identify contributing factors to traffic sign dirt, the chi-square test was employed To analyze the data and rank all of the factors based on their importance to the sign dirt, Random forests statistical model was utilized After analyzing the data, it can be concluded that ground elevation, sign mount height, and air pollution had the highest effect on making traffic signs dirty The findings of this investigation assist transportation agencies in determining traffic signs with a higher likelihood of sign dirt In this way, agencies would schedule to clean such traffic signs more frequently

Evaluating life cycle costs of perpetual pavements in China using operational pavement management system

Abstract: Highway transportation is considered as vital factor in China’s economic growth; many high grade highways have been constructed in China during the last decades. The research and application of perpetual asphalt pavement (PP) technology have been deployed in China since 2000. The semi-rigid pavement has been normally considered as typical pavement of high class highways in the design according to the Chinese experience. The objective of this research is to evaluate the performance of different Chinese perpetual pavements using operational pavement management system and to examine its suitability for use in the design and construction of more economical and durable pavements. It has been found that the use of thin asphalt layers over semi-rigid pavement foundation in PP structure will create more sustainable, economical, and durable PP structures in comparison with typical thick asphalt layers PP structures.

Analysis of moving bottlenecks considering a triangular fundamental diagram

Abstract: A significant number of research efforts have studied and analyzed the case in which a vehicle is moving slower than the traffic stream. This phenomenon, known as a moving bottleneck, results in a disruption of traffic flow and may significantly impact the traffic stream behavior upstream, downstream and abreast the slow moving vehicle. In this paper, a macroscopic approach for modeling moving bottlenecks is developed using microscopically derived data considering a triangular fundamental diagram. The passing flow rates of different moving bottleneck scenarios are determined using a previously developed microscopic model based on simulated data derived from the INTEGRATION software. Using the simulation results, an explicit expression of the bottleneck diagram, a flow-density relationship that defines the phenomenon macroscopically is proposed and the behavior of the traffic stream downstream and abreast the moving obstruction is depicted. It is demonstrated that the behavior of the traffic stream downstream of the slow vehicle as well as the acceleration behavior while passing is governed by the demand level. Such a result is coherent and consistent, to a significant extent, with two decades of research related to modeling moving bottlenecks and constitutes a potential feasible and more detailed description of the phenomenon in the case of a triangular fundamental diagram. Finally, it is noteworthy that the research subject of this paper could be considered as a first step in developing a numerical and practitioner-friendly framework for the analysis of moving bottlenecks that does not involve approaching the problem from its theoretical perspective.

Feasibility of perpetual pavement stage construction in China: A life cycle cost analysis

Abstract: The main objective of pavement design and management is to build sustainable pavement structure with minimum costs during its whole life. There are many uncertainties in the process of pavement design pertaining many of its variables, such as future traffic estimation, long time behavior of materials, future weights and types of traveling vehicles, availability of funds etc. Therefore, it is important to apply pavement stage construction technique during the process of pavement design and management to minimize the risk associated with these uncertainties. From the beginning of 2000, the research and application of perpetual asphalt pavement (PP) technology has been deployed in China. The semi rigid base for asphalt pavement has been normally considered as typical component of high class highways in the design according to the Chinese experience since 1997. The research objective is to apply pavement stage construction for the evaluation of life cycle costs of Chinese perpetual and traditional semi rigid pavements using operational pavement management system in addition to examine its suitability for design and construction of more economical and durable flexible pavements. It has been found that the stage construction of asphalt layers in PP over semi rigid pavement foundation will create more sustainable and trusted pavement structures in spite of 2–5% increase in present total cost.

Use of different exposure metrics for understanding multi-modal travel injury risk

Abstract: The objective of this work is to identify characteristics of different metrics of exposure for quantifying multi-modal travel injury risk. First, a discussion on the use of time-based and trip-based metrics for road user exposure to injury risk, considering multiple travel modes, is presented. The main difference between a time-based and trip-based metric is argued to be that a time-based metric reflects the actual duration of time spent on the road exposed to the travel risks. This can be proven to be important when considering multiple modes since different modes typically different speeds and average travel distances. Next, the use of total number of trips, total time traveled, and mode share (time-based or trip-based) is considered to compare the injury risk of a given mode at different locations. It is argued that using mode share the safety concept which focuses on absolute numbers can be generalized. Quantitative results are also obtained from combining travel survey data with police collision reports for ten counties in California. The data are aggregated for five modes: (i) cars, (ii) SUVs, (iii) transit riders, (iv) bicyclists, and (v) pedestrians. These aggregated data are used to compare travel risk of different modes with time-based or trip-based exposure metrics. These quantitative results confirm the initial qualitative discussions. As the penetration of mobile probes for transportation data collection increases, the insights of this study can provide guidance on how to best utilize the added value of such data to better quantify travel injury risk, and improve safety.

Using Stationary Image based Data Collection Method for Evaluation of Traffic Sign Condition

Abstract: Transportation asset management helps monitor the transportation systems and optimize the construction, operation, and maintenance of assets. Many state Department of Transportations (DOTs) have already established asset management systems for high cost and low quantity assets, e.g., bridge and tunnel assets. However, due to the sheer number of traffic signs deployed by DOTs, statewide sign inventory and condition information are not well developed. Currently, using handheld devices is the most selected method by agencies to measure signs. To address safety challenge and high cost of data collection, an innovative stationary image based method has recently been proposed. This paper discusses the advantages and disadvantages of such image based method over using handheld devices in terms of the accuracy, possibility and consistency of data, speed, safety, maintenance, and cost. At its completion, this study provides suggestions to tackle the issues associated with image based method.

Operations of electric taxis to serve advance reservations by trip chaining: Sensitivity analysis on network size, customer demand and number of charging stations

Abstract: This research investigated the performance of an Electric Taxi (ET) fleet that catered solely for customers with advance reservations. In a previously related research, a customized Paired Pickup and Delivery Problem with Time Window and Charging Station (PPDPTWCS) had been formulated to solve for the minimum number of taxis that would serve a fixed set of customer demand. The concept behind this fleet optimization was to chain multiple customer trips and trips to Charging Stations (CSs) to form a route and assigned to a taxi driver. In this paper the sensitivity of the ET fleet’s operations with respect to network sizes, customer demand densities and number of CSs have been investigated. It also analyzed the market shares of the CSs and the occupancy of a CS over time. The results showed that, (1) the expansion of network size or the increase in customer demand density led to increase in fleet size, number of trips to the CSs and maximum occupancies at the CSs but these performance measures grew at different rates; (2) when the network size and number of CSs were fixed, an increase in customer demand density led to a better utilization of taxis in terms of more customers served per taxi and higher average revenue per taxi; (3) given the same network size and demand density, the ET fleet’s performance was relatively insensitive to the number of CSs; and (4) the usage of individual CS was affected by the number of CS and their locations; and (5) when all the ETs were fully charged at the beginning of the same shift hour, they visited the CSs in bunches when their batteries were about to run out. These findings contribute to a better understanding of the operations of the ET fleet and the CSs. They could be used for making better decisions in the planning of ET operations.