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Transportation Research Part C: Emerging Technologies

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ISSN (Print) 0968-090X
Published by Elsevier

[2564 journals]

Urban link travel time estimation using large-scale taxi data with partial information
- Abstract: Publication date: August 2013
  Source:Transportation Research Part C: Emerging Technologies, Volume 33
  Author(s): Xianyuan Zhan , Samiul Hasan , Satish V. Ukkusuri , Camille Kamga
  Taxicabs equipped with Global Positioning System (GPS) devices can serve as useful probes for monitoring the traffic state in an urban area. This paper presents a new descriptive model for estimating hourly average of urban link travel times using taxicab origin–destination (OD) trip data. The focus of this study is to develop a methodology to estimate link travel times from OD trip data and demonstrate the feasibility of estimating network condition using large-scale geo-location data with partial information. The data, collected from the taxicabs in New York City, provides the locations of origins and destinations, travel times, fares and other information of taxi trips. The new model infers the possible paths for each trip and then estimates the link travel times by minimizing the error between the expected path travel times and the observed path travel times. The model is evaluated using a test network from Midtown Manhattan. Results indicate that the proposed method can efficiently estimate hourly average link travel times. This research provides new possibilities for fully utilizing the partial information obtained from urban taxicab data for estimating network condition, which is not only very useful but also is inexpensive and has much better coverage than traditional sensor data.
  
  PubDate: 2013-05-19T11:05:09Z
Enhancing the panic escape of crowd through architectural design
- Abstract: Publication date: Available online 17 May 2013
  Source:Transportation Research Part C: Emerging Technologies
  Author(s): Nirajan Shiwakoti , Majid Sarvi
  Doors and corridors are necessary architectural elements in public infrastructure such as transit stations, buildings and stadiums. Previous documented crowd disasters have showed that collective movement patterns are affected by the layout or the geometrical structure of the escape area. However, little study has been carried out to examine these interactions under panic situation due to scarcity of data on human panic. Here, we use bio-inspired approach to test if making appropriate architectural adjustments within a given escape area would change the collective movement patterns in a way that enhances the outflow of the crowd. First, we performed a series of experiment with ants under panic conditions to test the effect of different structural features to the panic escape in a chamber with fixed dimension. Results show that the adjustments can be effective by more than 90% in decreasing the evacuation time. We then scaled it up and simulated the situation to human scenario and found that the model prediction is consistent with those observed from the empirical data. The proposed method demonstrates that detailed analysis of microscopic effects of escape environment would be a potentially valuable additional perspective to aid in devising solutions that are efficacious and improve the safety of the crowd.
  
  PubDate: 2013-05-19T11:05:09Z
New driving control system with haptic feedback: Design and preliminary validation tests
- Abstract: Publication date: August 2013
  Source:Transportation Research Part C: Emerging Technologies, Volume 33
  Author(s): Jorge Juan Gil , Iñaki Díaz , Pablo Ciáurriz , Mikel Echeverría
  This paper presents a new mechatronic system that combines the capabilities of the steering wheel, the throttle and brake pedals in a single all-encompassing device. A two degree-of-freedom mechanism allows controlling all driving functionalities together in a very ergonomic and original way. The system uses drive-by-wire technology with haptic feedback for an outstanding driving experience. The device has been tested in a simulation platform, showing similar performance to conventional set of steering wheel and pedals, and very good acceptance among users. This work also surveys current drive-by-wire systems in the automotive industry and the use of haptic technology to assist drivers.
  
  PubDate: 2013-05-19T11:05:09Z
Scheduling of Intelligent and Autonomous Vehicles under pairing/unpairing collaboration strategy in container terminals
- Abstract: Publication date: August 2013
  Source:Transportation Research Part C: Emerging Technologies, Volume 33
  Author(s): Shahin Gelareh , Rochdi Merzouki , Kay McGinley , Roisin Murray
  A new class of Intelligent and Autonomous Vehicles (IAVs) has been designed in the framework of Intelligent Transportation for Dynamic Environment (InTraDE) project funded by European Union. This type of vehicles is technologically superior to the existing Automated Guided Vehicles (AGVs), in many respects. They offer more flexibility and intelligence in maneuvering within confined spaces where the logistic operations take place. This includes the ability of pairing/unpairing enabling a pair of 1-TEU (20-foot Equivalent Unit) IAVs dynamically to join, transport containers of any size between 1-TEU and 1-FFE (40-foot Equivalent) and disjoin again. Deploying IAVs helps port operators to remain efficient in coping with the ever increasing volume of container traffic at ports and eliminate the need for deploying more 40-ft transporters in the very confined area of ports. In order to accommodate this new feature of IAVs, we review and extend one of the existing mixed integer programming models of AGV scheduling in order to minimize the makespan of operations for transporting a set of containers of different sizes between quay cranes and yard cranes. In particular, we study the case of Dublin Ferryport Terminal. In order to deal with the complexity of the scheduling model, we develop a Lagrangian relaxation-based decomposition approach equipped with a variable fixing procedure and a primal heuristics to obtain high-quality solution of instances of the problem.
  
  PubDate: 2013-05-19T11:05:09Z
A model for enhancing robustness of aircraft and passenger connections
- Abstract: Publication date: July 2013
  Source:Transportation Research Part C: Emerging Technologies, Volume 32
  Author(s): Mohamed Ali Aloulou , Mohamed Haouari , Farah Zeghal Mansour
  Airlines schedules are often subject to various uncontrollable factors that cause disruptions and delays. These delays not only constitute, for many passengers, the painful part of air travel, but also represent for airlines a significant financial burden. In this paper, we present a model for building robust aircraft routes that are less vulnerable to disruptions through judiciously distributing slacks to connections where they are most needed operationally. Toward this end, the model assigns legs to aircraft and determines the flights departure times, while maintaining the designated time-slot assignments at airports, and satisfying operational constraints. The considered objective function is a newly proposed surrogate measure of robustness that implicitly captures the robustness both pertaining to aircraft and passenger connections. Computational experiments carried out on real-world-based instances, with up to 1278 flights and 251 aircraft, show that the model yields solutions that are remarkably robust. In particular, a simulation study reveals that the total delays, number of delayed flights, and number of missed connections can be significantly reduced.
  
  PubDate: 2013-05-07T11:05:33Z
Efficiency and equity of speed limits in transportation networks
- Abstract: Publication date: July 2013
  Source:Transportation Research Part C: Emerging Technologies, Volume 32
  Author(s): Shuaian Wang
  This paper examines the impact of speed limits on network efficiency, in terms of total travel time of all road users, and equity among road users from different origin–destination (OD) pairs, in terms of the change of travel time after imposing a speed limit scheme. We find that after imposing a speed limit scheme, the total travel time of all road users may decrease or increase; road users of some OD pairs may experience longer travel time, while other OD pairs may have shorter travel time. In view of the importance of speed limits on network efficiency and equity, we subsequently develop a bi-level programming model for designing the optimal speed limit scheme that maximizes the network efficiency while considering the equity issue. A global optimization approach that is suitable for bi-level programming models with finite discrete upper-level decision variables is proposed. Moreover, a conic quadratic mixed-integer linear programming approach is developed to solve relaxed models of the bi-level formulation of speed limit design. Two numerical examples are carried out.
  
  PubDate: 2013-05-07T11:05:33Z
Integrated macroscopic traffic flow, emission, and fuel consumption model for control purposes
- Abstract: Publication date: June 2013
  Source:Transportation Research Part C: Emerging Technologies, Volume 31
  Author(s): S.K. Zegeye , B. De Schutter , J. Hellendoorn , E.A. Breunesse , A. Hegyi
  Traffic control approaches based on on-line optimization require fast and accurate integrated models for traffic flow, emission, and fuel consumption. In this context, one may want to integrate macroscopic traffic flow models with microscopic emission and fuel consumption models, which can result in shorter simulation times with fairly accurate estimates of the emissions and fuel consumption. In general, however, macroscopic traffic flow models and microscopic emission and fuel consumption models cannot be integrated with each other. We provide a general framework to integrate these two kinds of models. We illustrate the approach by considering the macroscopic traffic flow model METANET 1 METANET Messmer and Papageorgiou (1990) stands for “Modèle d’Ecoulement du Trafic Autoroutier: NETwork”. 1 and the microscopic emission and fuel consumption model VT-micro, 2 VT-micro Ahn et al. (1999) stands for “Virginia Tech Microscopic”. 2 resulting in the so called the “VT-macro” model. Moreover, we characterize analytically the error introduced by the VT-macro model relative to the original VT-micro model. We further present an empirical analysis of the error and the computation time based on calibrated models of the Dutch A12 freeway.
  
  PubDate: 2013-05-03T11:07:04Z
Urban link travel time estimation based on sparse probe vehicle data
- Abstract: Publication date: June 2013
  Source:Transportation Research Part C: Emerging Technologies, Volume 31
  Author(s): Fangfang Zheng , Henk Van Zuylen
  In the urban signalized network, travel time estimation is a challenging subject especially because urban travel times are intrinsically uncertain due to the fluctuations in traffic demand and supply, traffic signals, stochastic arrivals at the intersections, etc. In this paper, probe vehicles are used as traffic sensors to collect traffic data (speeds, positions and time stamps) in an urban road network. However, due to the low polling frequencies (e.g. 1min or 5min), travel times recorded by probe vehicles provide only partial link or route travel times. This paper focuses on the estimation of complete link travel times. Based on the information collected by probe vehicles, a three-layer neural network model is proposed to estimate complete link travel time for individual probe vehicle traversing the link. This model is discussed and compared with an analytical estimation model which was developed by Hellinga et al. (2008). The performance of these two models are evaluated with data derived from VISSIM simulation model. Results suggest that the Artificial Neural Network model outperforms the analytical model.
  Highlights ► Travel times are estimated from sparse probe vehicles provided with GPS. ► A new method is introduced based on an Artificial Neural Network. ► Different estimation methods are compared for different traffic conditions. ► The ANN model performs better than Hellinga’s method with polling interval of 60s.
  
  PubDate: 2013-05-03T11:07:04Z
Calibration of a microscopic simulation model for emission calculation
- Abstract: Publication date: June 2013
  Source:Transportation Research Part C: Emerging Technologies, Volume 31
  Author(s): Li Jie , Henk Van Zuylen , Yusen Chen , Francesco Viti , Isabel Wilmink
  Emissions by road traffic can be reduced by optimising traffic control. The impact of this optimisation on emission can be analysed ex ante by simulation. The simulation programs used for this analysis should be valid with respect to the traffic characteristics that determine the emissions. Thus calibration of the parameters is a prerequisite. In most cases, volumes, travel times and queues are used to calibrate simulation models, rather than detailed driving characteristics such as speed and acceleration patterns. However, these driving behaviour parameters determine the vehicular emissions to a great extent. A study was carried out in which the driving behaviour parameters in a microscopic simulation model (VISSIM) were calibrated using real trajectories collected by image processing at an intersection in Rotterdam. The sensitivity of the simulation results for driving behaviour parameters was investigated. The most influential parameters were identified and adjusted to ensure that the simulation results were consistent with the observed traffic and could provide valid estimations of the total production of emissions.
  Graphical abstract Highlights ► A microscopic calibration of VISSIM for emission calculation. ► Use of vehicle trajectories from video registration. ► Saturation flow, speed and acceleration distribution as calibration target.
  
  PubDate: 2013-05-03T11:07:04Z
Editorial Board/Copyright Information
- Abstract: Publication date: June 2013
  Source:Transportation Research Part C: Emerging Technologies, Volume 31
  
  PubDate: 2013-05-03T11:07:04Z
A combined method to forecast and estimate traffic demand in urban networks
- Abstract: Publication date: June 2013
  Source:Transportation Research Part C: Emerging Technologies, Volume 31
  Author(s): Tobias Pohlmann , Bernhard Friedrich
  This paper presents a combined method for short-term forecasting of detector counts in urban networks and subsequent traffic demand estimation using the forecasted counts as constraints to estimate origin–destination (OD) flows, route and link volumes. The method is intended to be used in the framework of an adaptive traffic control strategy with consecutive optimization intervals of 15min. The method continuously estimates the forthcoming traffic demand that can be used as input data for the optimization. The forecasting uses current and reference space–time-patterns of detector counts. The reference patterns are derived from data collected in the past. The current pattern comprises all detector counts of the last four time intervals. A simple but effective pattern matching is used for forecasting. The subsequent demand estimation is based on the information minimization model that has been integrated into an iterative procedure with repeated traffic assignment and matrix estimation until a stable solution is found. Some enhancements including the improvement of constraints, redundancy elimination of these constraints and a travel time estimation based on a macroscopic simulation using the Cell Transmission Model have been implemented. The overall method, its modules and its performance, which has been assessed using artificially created data for a real sub-network in Hannover, Germany, by means of a microsimulation with Aimsun NG, are presented in this paper.
  
  PubDate: 2013-05-03T11:07:04Z
A random parameter ordered probit model to understand the mobilization time during hurricane evacuation
- Abstract: Publication date: July 2013
  Source:Transportation Research Part C: Emerging Technologies, Volume 32
  Author(s): Arif Mohaimin Sadri , Satish V. Ukkusuri , Pamela Murray-Tuite
  This paper presents a random parameters ordered probit model to capture underlying unobserved characteristics in the timing behavior of the evacuees that elapses in between their evacuation decision and actual evacuation i.e. the mobilization time for an evacuee. The ordered probit model has been developed by using Hurricane Ivan data and the estimation findings suggest that the mobilization time involves a complex interaction of variables related to household location, evacuation characteristics, and socio-economic characteristics among others. In the model, six variables- source and time of evacuation notice received, work constraint, previous hurricane experience, race and income- were found to be random and the random parameters (all normally distributed) suggest that their effect varies across the observations. In addition, the model introduces some new factors that impact the mobilization time (for example, the mobilization time for evacuees evacuating to public shelters is significantly lower) which have not been found in the earlier literature to the best of our knowledge. The findings of this study are useful to determine different fractions of people evacuating early or delaying for some time once they actually decide to evacuate, for a given socio-demographic profile. These fractions can be used in the future to develop more accurate dynamic travel demands for use in traffic simulation models.
  
  PubDate: 2013-04-29T11:06:04Z
The heterogeneous pickup and delivery problem with configurable vehicle capacity
- Abstract: Publication date: July 2013
  Source:Transportation Research Part C: Emerging Technologies, Volume 32
  Author(s): Yuan Qu , Jonathan F. Bard
  Various forms of the pickup and delivery problem (PDP) have been studied extensively over the past decades. This paper introduces a new version of the heterogeneous PDP in which the capacity of each vehicle can be modified by reconfiguring its interior to satisfy different types of customer demands. The work was motivated by a daily route planning problem arising at a senior activity center. A fleet of configurable vans is available each day to transport participants to and from the center as well as to secondary facilities for rehabilitative and medical treatment. The number of participants and support equipment that a van can accommodate depends on how it is configured. The problem is modeled as a mixed-integer program much the same way as a PDP but with side constraints that add another level of complexity. To find solutions, we developed a two-phase heuristic that makes use of ideas from greedy randomized adaptive search procedures with multiple starts. In phase I, a set of good feasible solutions is constructed using a series of randomized procedures. A representative subset of those solutions is selected as candidates for improvement by solving a max diversity problem. In phase II, an adaptive large neighborhood search (ALNS) heuristic is used to find local optima by reconstructing portions of the feasible routes. Specialized removal and insertion heuristics were designed for this purpose. Also, a specialized route feasibility check with vehicle type reassignment is introduced to take full advantage of the heterogeneous nature of vehicles. The effectiveness of the proposed methodology is demonstrated by comparing the solutions it provided over a period of several weeks with those that were used in practice and derived manually. The analysis indicates that anywhere from 30% to 40% savings can be achieved with the multi-start ALNS heuristic.
  
  PubDate: 2013-04-29T11:06:04Z
Framework for airspace planning and design based on conflict risk assessment Part 3: Conflict risk assessment model for airspace operational and current day planning
- Abstract: Publication date: July 2013
  Source:Transportation Research Part C: Emerging Technologies, Volume 32
  Author(s): Fedja Netjasov , Obrad Babić
  This paper presents a natural continuation of author’s previous work that deals with the development of a conflict risk assessment model for the purpose of airspace operational and current day planning under an airspace planning and design framework based on conflict risk and task-load assessment. The model is intended to support an air traffic manager’s decision-making process during sectorization (for a given set of available sectors determined at tactical planning levels) through the evaluation of conflict risk and air traffic controller task-load. The model is based on the assumption that a conflict between a pair of aircraft exists when either horizontal or vertical separation minima are violated. Additionally, it was assumed that risk is a random variable. The developed model allows for estimation of the number of conflicts and the conflict probability, as well as their distribution at intersections and along an airway. It also allows for the determination of the air traffic controller’s task-load for a given airspace and traffic load. The model is intended for use in en-route airspace. An illustration of the model application shows that in addition to airspace geometry, the total conflict risk also depends on aircraft speed, traffic demand and its spatial and temporal distribution in the airspace as well as the applied separation minima. Finally, it was shown that the results of the model could be used by the air traffic managers in order to help them decide the necessary grouping (aggregation) or collapsing (disaggregation) of sectors (sectorization).
  
  PubDate: 2013-04-29T11:06:04Z
Waiting zones for realistic modelling of pedestrian dynamics: A case study using two major German railway stations as examples
- Abstract: Publication date: Available online 22 April 2013
  Source:Transportation Research Part C: Emerging Technologies
  Author(s): Maria Davidich , Florian Geiss , Hermann Georg Mayer , Alexander Pfaffinger , Christian Royer
  The value of a pedestrian stream simulation depends on its ability to reproduce natural behaviour of pedestrians in different situations. Most models assume that pedestrians are single-minded and constantly move towards their destinations. However, our observations at two major German railway stations made during field experiments and our analysis of video recordings at one of these stations revealed that in virtually every setting a significant proportion of pedestrians do not walk continuously. Instead, they occasionally change their route in order to visit certain locations and stand there for a period of time. By waiting, they often block walking pedestrians and thereby influence the overall dynamics. In this paper, we evaluate the impact of waiting pedestrians and propose a model for waiting pedestrians based on cellular automata. The model is able to reproduce the observed pedestrian behaviour. We illustrate the model with simulations of several real life scenarios for a major German railway station and show that during rush hour standing pedestrians may prolong walking time by up to nearly 20%. We also demonstrate how the developed model can be used for the analysis of infrastructures, and prediction of problematic areas in public spaces.
  
  PubDate: 2013-04-25T11:06:23Z
A hybrid multi-scale approach for simulation of pedestrian dynamics
- Abstract: Publication date: Available online 18 April 2013
  Source:Transportation Research Part C: Emerging Technologies
  Author(s): A. Kneidl , D. Hartmann , A. Borrmann
  One of the most important aspects for a realistic prediction of pedestrian flows is the modelling of human navigation in normal situations such as early design phases of buildings or transportation systems and hubs as well as in evacuation studies to enhance safety in existing infrastructures. To overcome the limitations of current navigation models, this paper proposes a new hybrid multi-scale model, which closely links information between the small-scale and large-scale navigation layer to improve the navigational behaviour. In the presented hybrid navigation model, graph-based methods using visibility graphs are used to model large-scale wayfinding decisions. The pedestrians’ movements between two nodes of the navigation graph are modelled by means of a dynamic navigation field. The navigation field is updated dynamically during the runtime of the simulation, explicitly considering other pedestrians for determining the fastest path. The proposed hybrid approach provides a realistic modelling of human navigational behaviour and thus a realistic prediction of flows since it reflects the human cognitive processes triggered by wayfinding tasks. This includes taking into account other pedestrians for routing decisions who are visible from the current position of the considered pedestrian. The paper discusses the concept and the technical details of the proposed hybrid multi-scale approach in detail and presents an extensive case study demonstrating its advantages.
  Graphical abstract Highlights • Combining small-scale and large-scale navigational aspects allows increasing realism of pedestrian simulations. • The holistic multi-scale model enables fast recalculation of dynamic navigation fields. • The large-scale layer (nav. graph) divides the simulation area into many small fields. • Routing algorithms find more realistic routes by using values from the nav. fields. • Visible and invisible areas for each pedestrian can be easily distinguished.
  
  PubDate: 2013-04-21T11:05:51Z
A portfolio theory of route choice
- Abstract: Publication date: Available online 15 April 2013
  Source:Transportation Research Part C: Emerging Technologies
  Author(s): David Levinson , Shanjiang Zhu
  Although many individual route choice models have been proposed to incorporate travel time variability as a decision factor, they are typically still deterministic in the sense that the optimal strategy requires choosing one particular route that maximizes utility. In contrast, this study introduces an individual route choice model where choosing a portfolio of routes instead of a single route is the best strategy for a rational traveler who cares about both journey time and lateness when facing stochastic network conditions. The proposed model is compared with UE and SUE models and the difference in both behavioral foundation and model characteristics is highlighted. A numerical example is introduced to demonstrate how such model can be used in traffic assignment problem. The model is then tested with GPS data collected in metropolitan Minneapolis–St. Paul, Minnesota. Our data suggest there is no single dominant route (defined here as a route with the shortest travel time for a 15day period) in 18% of cases when links travel times are correlated. This paper demonstrates that choosing a portfolio of routes could be the rational choice of a traveler who wants to optimize route decisions under variability.
  
  PubDate: 2013-04-17T11:06:55Z
Editorial Board/Copyright Information
- Abstract: Publication date: May 2013
  Source:Transportation Research Part C: Emerging Technologies, Volume 30
  
  PubDate: 2013-04-13T12:36:11Z
Technical and economic evaluation of the floating container storage and transhipment terminal (FCSTT)
- Abstract: Publication date: May 2013
  Source:Transportation Research Part C: Emerging Technologies, Volume 30
  Author(s): Alfred J. Baird , Dirk Rother
  This paper presents a preliminary technical and economic evaluation for a new concept, the Floating Container Storage & Transhipment Terminal, or ‘FCSTT’. The main purpose of the FCSTT is considered to handle transhipment traffic, although its use could extend to supporting existing land-based terminals within ports. The paper considers a range of floating port structures already in operation, and other concepts yet to be developed. To an extent the FCSTT, which is based on conversion of a large container vessel, is an extension of these and other developments in different shipping sectors. The FCSTT can handle container cargo in offshore locations and/or wherever there is a need to provide ‘terminal’ infrastructure rapidly and at low cost. Our approach outlines design options for a FCSTT including analysis of crane preferences. The paper includes analysis of required storage capacity, and container handling productivity levels sufficient to ensure a practical terminal that is comparable with any landside facility, albeit with a focus on transhipment traffic. Thereafter the capital and operating costs for the FCSTT are estimated, with forecast cash flows based on assumed traffic volumes and competitive handling rates. Conclusions suggest the FCSTT offers potential for significant capital and operating cost savings compared to higher cost landside terminal infrastructure. Other key factors and advantages, including areas for further research, are highlighted.
  Highlights ► Floating terminals are common in bulk cargo yet limited in container shipping. ► Paper proposes floating container terminal (FCSTT) using second-hand container vessel. ► Best crane option for FCSTT is considered to be harbour slewing cranes. ► FCSTT costs estimated to be less than half that of comparable land terminal. ► FCSTT estimated to repay total investment cost in as little as 7years.
  
  PubDate: 2013-04-13T12:36:11Z
A space–time efficiency model for optimizing intra-intersection vehicle–pedestrian evacuation movements
- Abstract: Publication date: June 2013
  Source:Transportation Research Part C: Emerging Technologies, Volume 31
  Author(s): Zhixiang Fang , Qiuping Li , Qingquan Li , Lee D. Han , Shih-Lung Shaw
  The effectiveness of an evacuation plan is a central concern of emergency management agencies. Methodologies for assessing and optimizing the space–time use efficiency of an evacuation plan have yet to be studied satisfactorily. To this end, this paper proposes an assessment metric and uses it for the optimization of evacuation plans. First, we define a space–time use efficiency metric on the basis of trajectories on road segments and intersections. The metric measures the usage of an evacuation network by supporting a trajectory-based analysis of the competing behaviors of vehicles and pedestrians in a hybrid pedestrian-vehicle simulation. Secondly, we present a two-tier hybrid multi-objective optimization algorithm to plan vehicle and pedestrian turning movement directions in an integrated road and building-interior network for the purpose of making decisions about evacuation plans. This algorithm has three objectives: (i) minimizing average evacuation time, (ii) minimizing the overall length traveled, and (iii) maximizing space–time use efficiency in the evacuation network. The stadium at the Wuhan Sports Centre in China and its adjacent road network were chosen as the study environment. A total of 23,362 evacuees and 1362 vehicles were assumed for the evacuation experiments. The analysis results suggest that intra-intersection evacuation flows can significantly influence the space–time use efficiency of a evacuation plan. The proposed space–time use efficiency evaluation approach provides a practical method of measuring the effectiveness of evacuation plans.
  
  PubDate: 2013-04-13T12:36:11Z
New highway geometric design methods for minimizing vehicular fuel consumption and improving safety
- Abstract: Publication date: June 2013
  Source:Transportation Research Part C: Emerging Technologies, Volume 31
  Author(s): Min-Wook Kang , Shaghayegh Shariat , Manoj K. Jha
  This paper proposes separate computational methods for evaluating (1) fuel efficiency, (2) sight distance deficiencies and (3) expected accident costs for a given highway alignment, depending on its detailed geometric characteristics. A fuel consumption model is developed based on two important concepts: (i) variability in the amount of fuel consumed by vehicles depending on variability in highway geometry and (ii) minimization of the fuel consumption by ensuring conditions suitable for driving at cruising speed. The methods estimate the fuel consumption by integrating vehicle propulsive force necessary to maintain the cruising speed from the beginning to the end of an alternative highway being evaluated. A sight distance model that not only automatically calculates available sight distance (ASD) and stopping sight distance (SSD), but also evaluates sight distance deficiency of alternative alignments is proposed. The total sight distance deficiency of an alternative alignment is estimated based on (i) the length of the road segments where ASD<SSD and (ii) the significance of sight distance restriction. A crash prediction model proposed in the Highway Safety Manual (HSM) is adopted to evaluate and compare alternative alignments from safety perspective. A case study is presented to demonstrate the effectiveness of the developed methods. These methods will be integrated into a highway alignment optimization model (HAO) previously developed by the authors to evaluate numerous possible alternative alignments of a new highway system through tradeoffs among various relevant decision criteria. Those criteria may include vehicle fuel efficiency, sight distance, and safety, besides various cost factors, such as the construction cost, maintenance cost, user cost, and environmental impact cost. Such an integrated modeling framework will help evaluate green and environmentally sustainable highways. Many extensions of the work remain to be worked in the future, for example: (1) the effects of gain in propulsive force when traveling down from the crest of a curve; and (2) variability in fuel consumption rate based on vehicle type, gradient, critical length of grade, weather, and other factors.
  
  PubDate: 2013-04-13T12:36:11Z
Speed-based toll design for cordon-based congestion pricing scheme
- Abstract: Publication date: June 2013
  Source:Transportation Research Part C: Emerging Technologies, Volume 31
  Author(s): Zhiyuan Liu , Qiang Meng , Shuaian Wang
  The cordon-based Electronic Road Pricing (ERP) system in Singapore adopts the average travel speed as an index for evaluating the traffic congestion within a cordon area, and the maintenance of the average travel speed within a satisfactory range is taken as the objective of the toll adjustment. To formulate this practical speed-based toll design problem, this paper proposes a mathematical programming with equilibrium constraint (MPEC) model with the objective of maintaining the traffic condition in the cordon area. In the model, the network users’ route choice behavior is assumed to follow probit-based stochastic user equilibrium with elastic demand, asymmetric link travel time functions and continuous value-of-time. A distributed revised genetic algorithm is designed for solving the MPEC model. Finally, a network example based on the ERP system is adopted to numerically validate the proposed models and algorithms, and further indicates that the computation speed can be improved greatly by using a distributed computing system.
  Highlights ► To improve the traffic condition in cordon area is taken as a pricing objective. ► Travel speed is employed to measure the traffic condition. ► Users’ route choice behavior follows probit-based SUE problem with continuous VOT. ► A MPEC model is proposed for the speed-based toll design problem. ► A distributed revised genetic algorithm is developed to solve the MPEC model.
  
  PubDate: 2013-04-13T12:36:11Z
Bounded-rationality based day-to-day evolution model for travel behavior analysis of urban railway network
- Abstract: Publication date: June 2013
  Source:Transportation Research Part C: Emerging Technologies, Volume 31
  Author(s): Jianjun Wu , Huijun Sun , David Z.W. Wang , Ming Zhong , Linghui Han , Ziyou Gao
  Existing day-to-day traffic assignment models are all built to capture day-to-day traffic fluctuations, but most of the evolution process itself and the final equilibrium state are based on the assumption of passengers’ rational behavior, that is, to find the path with the minimum travel cost, which ignore the correlation among the days’ evolution and boundedly rational (BR) of travelers in the path choice and thus can give very unreasonable results for ones with this behavior. Such an assumption basically ignores the correlation among day-to-day evolution and bounded rationality (BR) of travelers in the path choice and thus could result in inaccurate results for the travelers with such behavior. This paper proposes a day-to-day dynamic evolution model with the consideration of BR, which can better captures travelers’ characteristics in the path finding within an urban railway network. In order to capture the correlation of path choice over time, we introduce a time series method, detrended fluctuation analysis (DFA), to analyze the complex long-term correlations hiding in the passengers’ evolution over time. The study results clearly show that the proposed model and analytical approach is better for capture the day-to-day dynamics in travel behaviors and can serve as a general framework of modeling passengers’ BR behavior.
  Highlights ► A day-to-day evolution model based on bounded-rationality is developed. ► DFA is introduced to capture the correlation of travelers’ route choice decision. ► Effects of key factors in URT system on DFA scale exponent are analyzed. ► Statistical self-affinity and long range correlation process are discovered.
  
  PubDate: 2013-04-13T12:36:11Z
Costs and benefits of the European directive on road tolling interoperability
- Abstract: Publication date: May 2013
  Source:Transportation Research Part C: Emerging Technologies, Volume 30
  Author(s): Carl J. Hamilton , Jonas Eliasson
  Pricing of road use in the form of tolls, congestion charges, kilometre tax and other similar schemes, is becoming increasingly common. Each toll road operator has so far decided on its own how to design and implement systems for collecting road user charges, causing a plethora of system and scheme designs. As a measure to reduce the drawbacks of such differences, the European Union has passed legislation aiming at making available interoperable road charging services, valid across all charging systems a vehicle might pass during a European journey. This legislation is setting the bar high, requiring that virtually every charging system in the Union be covered. We analyse the costs and benefits caused by this regulation, and if an adjusted regulation can improve these results. We conclude that the new legislation yields a social loss ranging from 100 to just above 500 million Euros annually. Policy suggestions to improve this result are also provided.
  Highlights ► Interoperability can be achieved in different ways, by means of harmonisation or via adapters. ► EU legislation on road tolling places high requirements on interoperability, mainly by adapters. ► The costs of the legislation far outweigh the benefits.
  
  PubDate: 2013-04-13T12:36:11Z
Editorial on transportation economics
- Abstract: Publication date: May 2013
  Source:Transportation Research Part C: Emerging Technologies, Volume 30
  Author(s): Robin Lindsey
  
  PubDate: 2013-04-13T12:36:11Z
A revealed-preference study of behavioural impacts of real-time traffic information
- Abstract: Publication date: May 2013
  Source:Transportation Research Part C: Emerging Technologies, Volume 30
  Author(s): Yin-Yen Tseng , Jasper Knockaert , Erik T. Verhoef
  In the present study, we investigate the impact of real-time traffic information on traveller behaviour by using repeated day-to-day revealed-preference (RP) observations from a reward experiment. We estimate a trip scheduling model of morning peak behaviour that allows us to determine the impact of traffic information on travel behaviour. Specifically, we distinguish between the marginal impact of expected travel times versus that of deviations from this expectation upon user behaviour. We find that participants to the experiment who were given access to a smart-phone displaying real-time traffic information react to the daily variations in travel times stronger than they had done in the pre-trial period. This we interpret as evidence that provision of traffic information indeed affects behaviour. However, we also find that participants who were not given the smart-phone also respond to daily variations in travel times – suggesting that these drivers use other sources of information to help their trip planning, or were better capable of processing information available into travel time predictions.
  
  PubDate: 2013-04-13T12:36:11Z
A green reform is not always green
- Abstract: Publication date: May 2013
  Source:Transportation Research Part C: Emerging Technologies, Volume 30
  Author(s): Mogens Fosgerau , Thomas C. Jensen
  This paper analyses a tax reform, explicitly conceived by policy makers to be climate-friendly, that partly replaces a high vehicle registration tax by road user charging and allows for differentiation of the remaining registration tax by fuel efficiency. A microeconomic framework is proposed to analyse such a reform. For the case of Denmark, the analysis shows that the reform is likely to yield a significant and robust welfare gain. However, it seems not unlikely that CO2 emissions from passenger cars may increase as a result of the reform.
  Highlights ► Evaluates a reform that partly replaces registration tax for cars by road pricing. ► This reform is designed to be green. ► Microeconomic model analysis shows that the reform is likely to yield a welfare gain. ► It may, however, lead to increased CO2 emission.
  
  PubDate: 2013-04-13T12:36:11Z
An integrated case-based reasoning approach for personalized itinerary search in multimodal transportation systems
- Abstract: Publication date: June 2013
  Source:Transportation Research Part C: Emerging Technologies, Volume 31
  Author(s): Amna Bouhana , Afef Fekih , Mourad Abed , Habib Chabchoub
  Suggesting personalized itinerary search for travelers in a multimodal transportation system is a challenging problem. This is due to the increased complexity and diversity of transportation means, the intricacy and multitude of destinations along with the amount of rapidly changing information available to the traveler. Providing the transportation user with the relevant information that only meets his needs, preferences and personal profile is of foremost importance in efficiently supporting passenger mobility requirements in a large urban agglomeration. In this paper, we propose a multi-criteria approach for suggesting personalized itinerary to transportation users based on their preferences and needs. The proposed approach integrates case-based reasoning with Choquet integral to suggest the itinerary that best matches the user’s preferences. Further, the proposed method predicts the user’s behavior by comparing his preferences to those of other users with the same preferences for a given context. This will help the user to adopt the best action when facing a new situation in his itinerary search. This will help the user adopt the best action facing a new situation. Personalized information retrieval is processed based on criteria which weights are determined using the two-additive Choquet integral. The performance of the proposed algorithm was assessed by solving a real-life itinerary planning problem defined in the Tunisian urban public transit network. A comparison study involving both qualitative and quantitative assessment of the proposed approach as compared to two other methods was also carried out. Based on the performance analysis, as well as the comparison study, our new approach provides the best solutions for applications requiring personalization based user’s preferences in a multi-criteria setting.
  
  PubDate: 2013-04-13T12:36:11Z
A study of freeway drivers’ demand for real-time traffic information along main freeways and alternative routes
- Abstract: Publication date: June 2013
  Source:Transportation Research Part C: Emerging Technologies, Volume 31
  Author(s): Rong-Chang Jou , Ke-Hong Chen
  A computer-aided survey was designed and conducted face-to-face with freeway drivers in Taiwan to gauge the demand for and reasonable pricing of customized real-time traffic information in the event of three different traffic conditions. Bivariate ordered probit models were estimated to investigate factors that significantly influence the demand for traffic information both for main freeways and secondary alternative routes. The results indicated that the demand for traffic information for non-recurring conditions was the strongest of the factors investigated. Basic information was the main type of information requested for normal and recurring conditions, whereas dynamic travel time prediction was the main type of information requested for non-recurring conditions. The estimation results from bivariate ordered probit models showed that by providing node-to-node information and encouraging a greater willingness to pay for information the demand for traffic information about main freeways and secondary alternative routes will increase. Finally, the significant and positive correlations of models imply that the greater the demand for traffic information about main freeways, the greater the demand for information about secondary alternative routes.
  Highlights ► Bivariate ordered probit models were used to investigate factors influencing the demand for traffic information. ► The results indicated the demand for traffic information for non-recurring conditions was the strongest. ► Basic information was the main type of information requested for normal and recurring conditions. ► Dynamic travel time prediction was the main type of information requested for non-recurring conditions. ► The demand for traffic information about main highways and secondary alternative routes was positively correlated.
  
  PubDate: 2013-04-13T12:36:11Z
A new concept of occupancy: Dynamic time occupancy
- Abstract: Publication date: June 2013
  Source:Transportation Research Part C: Emerging Technologies, Volume 31
  Author(s): Chong Zi Xiao , Jin Xin Cao , Zheng Yu Wang
  Occupancy is widely used in traffic flow theory. As a static parameter, however, the traditional occupancy cannot provide a comprehensive description of traffic performance. Based on previous studies, given the minimum safety distance between two adjacent vehicles in the same lane, the dynamic space occupancy (DSO) is redefined and a new parameter, namely the dynamic time occupancy (DTO), is proposed in this paper. It is found that the reaction time and the average time gaps are equivalent under congested condition, and this results in an equivalence relationship between the DTO model and the average time gaps model. Also, a new congested traffic fundamental diagram is derived, which is similar to the triangular traffic flow model. The analysis of a large set of the field data shows that DTO is always equal or close to 1 under congested condition. It is found that the reaction time has a great influence on highway capacity when DTO equals 1, and this may be useful for the capacity analysis or improvement. Different from the traditional static occupancy, DTO is a dynamic parameter that can provide a more fitting description of the occupying relationship between vehicles and highways.
  
  PubDate: 2013-04-13T12:36:11Z
Estimation of travel time and the benefits of upgrading the fare payment technology in urban bus services
- Abstract: Publication date: May 2013
  Source:Transportation Research Part C: Emerging Technologies, Volume 30
  Author(s): Alejandro Tirachini
  Multiple regression models are estimated to analyse bus travel times in an urban network. We identify variables that have a significant influence on the variation of bus travel time, and estimate the percentage of time that buses take at each stage of a trip (i.e., non-stop running time, delay due to traffic lights, delay due to roundabouts and time lost at bus stops), which is useful to categorise the sources of delay along a route. By using estimates of passenger boarding times with alternative fare payment methods (cash, magnetic strip, contactless card and off-board payment), we calculate operational speed and benefits of upgrading the fare payment technology, including savings on fleet size requirements, fuel and labour cost, travel time for users and air pollution. A comparative assessment of speed gains with two policies aimed at reducing bus travel times – providing dedicated busways and upgrading the fare collection system – shows that the number of passengers is crucial in determining the advantage of one or the other in increasing bus operating speed.
  
  PubDate: 2013-04-13T12:36:11Z
A socio-economic analysis of Smart Infrastructure sensor technology
- Abstract: June 2013
  Publication year: 2013
  Source:Transportation Research Part C: Emerging Technologies, Volume 31
  
  Smart Infrastructure wireless sensor technology is designed to provide a new way of managing infrastructure. These wireless sensors are able to share information on infrastructure conditions across a range of agencies without human intervention. Thus, false readings can be corrected automatically and further incidents should be avoided. The advantages of using these wireless sensors are their reliability, low-cost, low power and fast deployment characteristics. In this paper, we conduct a socio-economic analysis on the application of Smart Infrastructure sensor technology to the British rail tunnel industry using Monte Carlo simulation. The study would offer insights on the feasibility of the technology. Furthermore, the simulation forecast would bring the deeper understanding of the wider socio-economic implications, which is important for decision makers. Our study shows that the mean value of the cumulative net present value for the application of the Smart Infrastructure sensor to the British tunnel market in the year 2056 is estimated to be US$40million. According to the sensitivity analysis, the key parameters, which have significant impacts on the net present value, are the maximum target market penetration rate, base year disruption cost due to tunnel closure, total tunnel length, and annual number of tunnel collapses.
  
  PubDate: 2013-04-05T17:05:14Z
Decentralized evacuation management
- Abstract: June 2013
  Publication year: 2013
  Source:Transportation Research Part C: Emerging Technologies, Volume 31
  
  Evacuation is an urgent measure of disaster response. It requires route planning by many individual agents under circumstances that include the agents’ limited knowledge of their environment, an unknown impact of the disaster on the environment, and potentially destroyed, blocked, congested or lacking communication infrastructure. These circumstances impede any straightforward approach to evacuation planning. Neither are individuals able to determine an optimal route, nor is a centralized service able to determine or communicate routes to individuals. This paper suggests and investigates a novel paradigm for evacuation management: decentralized planning based on sharing local knowledge in a peer-to-peer manner. The paradigm is independent from external communication infrastructure, adapts to dynamic disasters, and turns out to be in many scenarios as successful as centralized management. Results have implications for disaster management practice, and cooperative intelligent transport in general.
  Highlights ► Collaboration in evacuation is highly beneficial. ► Agents achieve same evacuation performance as global management in many settings. ► Approach is robust to infrastructure failure and independent of specific environment. ► This novel paradigm should be considered in disaster management in the future.
  
  PubDate: 2013-04-01T11:04:50Z
Behavioural changes in drivers experiencing highly-automated vehicle control in varying traffic conditions
- Abstract: May 2013
  Publication year: 2013
  Source:Transportation Research Part C: Emerging Technologies, Volume 30
  
  Previous research has indicated that high levels of vehicle automation can result in reduced driver situation awareness, but has also highlighted potential benefits of such future vehicle designs through enhanced safety and reduced driver workload. Well-designed automation allows drivers’ visual attention to be focused away from the roadway and toward secondary, in-vehicle tasks. Such tasks may be pleasant distractions from the monotony of system monitoring. This study was undertaken to investigate the impact of voluntary secondary task uptake on the system supervisory responsibilities of drivers experiencing highly-automated vehicle control. Independent factors of Automation Level (manual control, highly-automated) and Traffic Density (light, heavy) were manipulated in a repeated-measures experimental design. 49 drivers participated using a high-fidelity driving simulator that allowed drivers to see, hear and, crucially, feel the impact of their automated vehicle handling. Drivers experiencing automation tended to refrain from behaviours that required them to temporarily retake manual control, such as overtaking, resulting in an increased journey time. Automation improved safety margins in car following, however this was restricted to conditions of light surrounding traffic. Participants did indeed become more heavily involved with the in-vehicle entertainment tasks than they were in manual driving, affording less visual attention to the road ahead. This might suggest that drivers are happy to forgo their supervisory responsibilities in preference of a more entertaining highly-automated drive. However, they did demonstrate additional attention to the roadway in heavy traffic, implying that these responsibilities are taken more seriously as the supervisory demand of vehicle automation increases. These results may dampen some concerns over driver underload with vehicle automation, assuming vehicle manufacturers embrace the need for positive system feedback and drivers also fully appreciate their supervisory obligations in such future vehicle designs.
  Highlights ► Drivers show more of a propensity to become involved with in-vehicle entertainment tasks. ► Drivers are receptive to the demands of heavy traffic, focussing more attention to the roadway than in light traffic. ► Drivers change lanes less frequently in order to overtake slower moving traffic.
  
  PubDate: 2013-03-28T12:06:04Z
Empirical observations of capacity drop in freeway merges with ramp control and integration in a first-order model
- Abstract: May 2013
  Publication year: 2013
  Source:Transportation Research Part C: Emerging Technologies, Volume 30
  
  An accurate density monitoring along a stretch of a freeway, especially under congested time-variant conditions is necessary to evaluate congestion levels, understand complex traffic phenomena and develop efficient control strategies. In the first part of the paper (i) we show empirical evidence from freeway-ramp merges in Twin Cities freeway system, in favor of the capacity drop phenomenon, (ii) we provide a methodology based on phase diagrams to quantitatively estimate the level of the drop, (iii) we show that the level of the drop depends on the ratio of mainline vs. ramp flow and (iv) we investigate whether implementation of control strategies has an effect on the value of capacity drop. In the second part of the paper, we develop a methodology to estimate densities with space and time based on data from loop detectors, by integrating the capacity drop. The methodology is based on solving a flow conservation differential equation (using LWR theory) with intermediate (internal) freeway mainline boundaries, which is faster and more accurate from approaches using only external boundaries. To capture the capacity drop phenomenon into the first-order model we utilize a fundamental diagram with two values of capacity and we provide a memory-based methodology to choose the appropriate value in the numerical solution of the problem with a Godunov scheme. Results compared with real data and micro-simulation of a long freeway stretch show that this model produces more reliable and accurate results than previous theories.
  Highlights ► Provide empirical evidence from freeway-ramp merges in favor of capacity drop phenomena. ► Provide a methodology based on phase diagrams to quantitatively estimate the level of drop. ► Show that the ratio of mainline vs. ramp flows has a significant effect to the level of drop. ► Integrate capacity drop phenomena to a first-order traffic model.
  
  PubDate: 2013-03-28T12:06:04Z
High speed rail passengers’ mobile ticketing adoption
- Abstract: May 2013
  Publication year: 2013
  Source:Transportation Research Part C: Emerging Technologies, Volume 30
  
  This study examines high speed rail (HSR) passengers’ acceptance of mobile ticketing services, as indicated by their mobile access for ticketing information inquiries and use of quick response codes (QR codes) for payment and gate entrance. This study contributes to developing a theoretical framework that brings together mental accounting theory and the technology acceptance model (TAM) to examine consumers’ decision to adopt mobile ticketing. Structural equation modeling was adopted to examine the research hypotheses based on the proposed theoretical framework. The analytical results provide empirical evidence that a combination of the mental accounting theory and TAM is appropriate for explaining passengers’ mobile ticketing service adoption. The findings demonstrate that personal innovativeness has a positive effect on the both mobile access adoption and QR code adoption. Although perceived risk, perceived usefulness, and perceived ease of use all influence QR code adoption, mobile access adoption is not directly affected by perceived risk or perceived ease of use. However, the perceived usefulness associated with such a system has a positive and direct influence on mobile access adoption. Moreover, the findings with respect to the interaction between potential benefit and potential loss of adopting a QR code service show that perceived risk not only directly affects passengers’ mobile ticketing adoption but also offsets the influence of the construct of “perceived usefulness” on passengers’ adoption intention. The conclusions of this study have managerial implications for HSR system operators and may be generalized to the application of mobile ticketing in other transportation industries.
  Highlights ► Mental accounting theory was served as theoretical foundation. ► Structural equation modeling was adopted for examining the research hypotheses. ► Personal innovativeness has a positive effect on the acceptance of mobile ticketing. ► Perceived risk can significantly offset the influence of perceived usefulness. ► This study has managerial implications for promoting mobile ticketing.
  
  PubDate: 2013-03-28T12:06:04Z
A stochastic model for design and evaluation of chain collision avoidance applications
- Abstract: May 2013
  Publication year: 2013
  Source:Transportation Research Part C: Emerging Technologies, Volume 30
  
  Cooperative/Chain Collision Avoidance (CCA) is an important type of safety-related applications of vehicular ad hoc networks (VANETs). They provide collaborative communication capabilities to vehicles in order to reduce the number of accidents on the road. Simulation is the usual choice to evaluate these systems. However, current simulation tools based on car-following models cannot be seamlessly used to simulate accidents, as we discuss here. Therefore, in this paper we propose the use of a stochastic model as an alternative to simulation for the design and performance evaluation of such applications. The model enables the computation of the average number of collisions that occurs in a platoon of vehicles, the probabilities of the different ways in which the collisions may take place, as well as other statistics of interest. The suitability of the model for evaluating CCA applications is shown by comparing our results with other authors’ simulation results. Additionally, it can be used at an early stage to shed relevant guidelines for the design of CCA applications, by disclosing the influence of kinematic parameters on the collision process. To exemplify it, we provide an evaluation of different types of CCA applications in two scenarios, a freeway and an urban scenario.
  Highlights ► We discuss the limitations of current simulators regarding accident simulation. ► We use a stochastic model for the design and evaluation of CCA applications. ► The probabilities of the different ways in which collisions may occur are computed. ► Relevant guidelines for the design of CCA applications can be disclosed. ► We provide an evaluation of different types of CCA applications in two scenarios.
  
  PubDate: 2013-03-28T12:06:04Z
Path inference from sparse floating car data for urban networks
- Abstract: May 2013
  Publication year: 2013
  Source:Transportation Research Part C: Emerging Technologies, Volume 30
  
  The use of probe vehicles in traffic management is growing rapidly. The reason is that the required data collection infrastructure is increasingly in place in urban areas with a significant number of mobile sensors constantly moving and covering expansive areas of the road network. In many cases, the data is sparse in time and location and includes only geo-location and timestamp. Extracting paths taken by the vehicles from such sparse data is an important step towards travel time estimation and is referred to as the map-matching and path inference problem. This paper introduces a path inference method for low-frequency floating car data, assesses its performance, and compares it to recent methods using a set of ground truth data.
  Highlights ► A map-matching and path inference algorithm for sparse GPS probes is introduced. ► It assumes limited information (only coordinates and timestamp) is available. ► Global criteria are used to identify the path corresponding to observed probes. ► The method demonstrates superior performance compared to similar algorithms. ► It performs efficiently in both off-line and on-line applications.
  
  PubDate: 2013-03-24T12:04:46Z
Implementation and test of a hybrid storage system on an electric urban bus
- Abstract: May 2013
  Publication year: 2013
  Source:Transportation Research Part C: Emerging Technologies, Volume 30
  
  Customer acceptance of Battery Electric Vehicles (BEVs) depends strongly on the performance of the Energy Storage System (ESS). Energy density, power density and lifetime of ESSs are three key parameters to be optimized in a BEV. For this purpose the use of a hybrid energy source on board of electric vehicles has been proposed and analyzed in literature. However, most of the previous studies have been limited to simulation or to test bench experiments of the ESS. This paper focuses on the implementation and use of the association of high energy NiCd battery and high power supercapacitors on board of a 3.5t urban bus. An uncomplicated and efficient energy management strategy has been implemented and tested. The behavior of the vehicle has been investigated by experiment on a roller test bench for two different driving cycles, highlighting the effects of the hybridization: reduction of losses within the battery with consequent expected lifetime extension, improved dynamic of the vehicle and a possible driving range extension.
  Highlights ► Implementation and use of a hybrid sour NiCd battery and supercapacitors. ► Investigation, by experiment, of the 3.5t urban bus behavior on a roller bench. ► Use of two different real-world recorded driving cycles. ► Losses reduction within the battery is settled by temperature measurements. ► Driving range extension is possible due to better sustaining of the main DC link.
  
  PubDate: 2013-03-16T12:06:44Z
Editorial Board/Copyright Information
- Abstract: April 2013
  Publication year: 2013
  Source:Transportation Research Part C: Emerging Technologies, Volume 29
  
  PubDate: 2013-03-16T12:06:44Z
An adaptive control algorithm for traffic-actuated signals
- Abstract: May 2013
  Publication year: 2013
  Source:Transportation Research Part C: Emerging Technologies, Volume 30
  
  A real-time, on-line control algorithm is proposed that aims to maintain the adaptive functionality of actuated controllers while improving the performance of traffic-actuated signal control system. To be consistent with the operation logic of existing signal control devices, only those four basic control parameters that can be found in modern actuated controllers are considered: phase sequence, minimum green, unit extension and maximum green. Microscopic simulation is used to test and evaluate the proposed control algorithm comparing with free-mode actuated, actuated-coordinated and volume–density control in a calibrated signalized network. Simulation results indicate that the proposed algorithm has the potential to improve the performance of the network at different traffic demand levels.
  
  PubDate: 2013-03-16T12:06:44Z
An algorithm for improved performance of railway condition monitoring equipment: Alternating-current point machine case study
- Abstract: May 2013
  Publication year: 2013
  Source:Transportation Research Part C: Emerging Technologies, Volume 30
  
  This paper develops a new approach for fault detection and diagnosis utilising parameters collected from low-cost and accessible sensors. An electrical railway point machine within a railway junction is used as a case study. The paper shows that electrical active power collected from electrical current and electrical voltage sensors can be used for condition monitoring systems. The methodology proposed in this paper utilises Wavelet Transforms and Support Vector Machines. It was found that together these methods can detect and diagnose misalignment faults of electrical railway point machine to a high degree of accuracy. Furthermore, it was proved that the approach can provide an indication of the severity of the faults. This work was carried out in collaboration between the University of Birmingham and Central Japan Railway Company.
  Highlights ► The paper aims to develop a robust approach to fault diagnosis of point machines. ► Drive force, current and voltage data were collected and analysed. ► A k-means clustering algorithm was used to find an appropriate parameter. ► The methodology proposed utilises Wavelet Transforms and Support Vector Machines. ► It was found that the method can diagnose faults to a high degree of accuracy.
  
  PubDate: 2013-03-16T12:06:44Z
A new street connectivity indicator to predict performance for feeder transit services
- Abstract: May 2013
  Publication year: 2013
  Source:Transportation Research Part C: Emerging Technologies, Volume 30
  
  This paper defines a novel street Connectivity Indicator (C.I.) to predict transit performance by identifying the role that street network connectivity plays in influencing the service quality of demand responsive feeder transit services. This new C.I. definition is dependent upon the expected shortest path between any two nodes in the network, includes spatial features and transit demand distribution information and is easy to calculate for any given service area. Simulation analyses over a range of networks have been conducted to validate the new definition. Results show a desirable monotonic relationship between transit performance and the proposed C.I., whose values are directly proportional and therefore good predictors of the transit performance, outperforming other available indicators, typically used by planners.
  Highlights ► We defined the expected shortest path among any two demand points of a network. ► We developed a connectivity index to predict Demand Responsive Transit performance. ► We validated the new index by simulation.
  
  PubDate: 2013-03-16T12:06:44Z
An electromechanical moving load fixed node position and fixed node number railway power supply systems optimization model
- Abstract: May 2013
  Publication year: 2013
  Source:Transportation Research Part C: Emerging Technologies, Volume 30
  
  This paper presents an optimization model for simulations of railway power supply systems. It includes detailed power systems modeling, train movements in discretized time considering running resistance and other mechanical constraints, and the voltage-drop-induced reduction of possible train tractive forces. The model has a fixed number of stationary power system nodes, which alleviates optimized operation over time. The proposed model uses SOS2 (Special Ordered Sets of type 2) variables to distribute the train loads to the two most adjacent power system nodes available. The impacts of the number of power system nodes along the contact line and the discretized time step length on model accuracy and computation times are investigated. The program is implemented in GAMS. Experiences from various solver choices are also discussed. The train traveling times are minimized in the example. Other studies could e.g. consider energy consumption minimization. The numerical example is representative for a Swedish decentralized, rotary-converter fed railway power supply system. The proposed concept is however generalizable and could be applied for all kinds of moving load power system studies.
  Highlights ► A fixed node model for moving loads in electric power supply systems is developed. ► The model is made for moving trains in a railway power supply system. ► SOS2 variables, variables of special ordered sets of type 2 are used in the model. ► Detail richness of power system depends on number of nodes and node placing. ► Fixed nodes allow railway power system operation optimization over time.
  
  PubDate: 2013-03-16T12:06:44Z
Optimal routing for automated highway systems
- Abstract: May 2013
  Publication year: 2013
  Source:Transportation Research Part C: Emerging Technologies, Volume 30
  
  We present a routing guidance approach that can be used in Automated Highway Systems (AHS). We consider automated highway systems in which intelligent vehicles organised in platoons drive to their destination, controlled by a hierarchical control framework. In this framework there are roadside controllers that provide speed and lane allocation instructions to the platoons. These roadside controllers typically manage single stretches of highways. A collection of highways is then supervised by so-called area controllers that mainly take care of the route guidance instructions for the platoons and that also coordinate the various roadside controllers in their area. In this paper we focus on the optimal route choice control problem for the area controllers. In general, this problem is a non-linear integer optimisation problem with high computational requirements, which makes the problem intractable in practice. Therefore, we first propose a simplified but fast simulation model to describe the flows of platoons in the network. Next, we show that the optimal route choice control problem can be approximated by a mixed-integer linear problem. Later, we describe a new METANET-like model to describe the flow of platoons in the AHS. With a simple case study we illustrate that both approaches result in a balanced trade-off between optimality and computational efficiency.
  Highlights ► We consider efficient route guidance control for platoons of autonomous vehicles. ► The first control approach we propose is based on mixed-integer linear programming. ► The second approach uses real-valued non-linear programming. ► Both provide a balanced trade-off between optimality and computational efficiency.
  
  PubDate: 2013-03-08T11:22:11Z
Optimal subwork zone length and project start time for short-term daytime work zones from the contractor’s perspective
- Abstract: April 2013
  Publication year: 2013
  Source:Transportation Research Part C: Emerging Technologies, Volume 29
  
  To mitigate the negative traffic impact caused by work zones, land transport authorities usually impose constraints on queue length and travel delay. In reality, a single or multiple subwork zone strategy can be adopted to mitigate queue length and travel delay. However, contractors conducting work projects are only concerned with the minimization of the total maintenance cost. From the contractor’s standpoint, this study proposes a total maintenance cost minimization model to determine the optimal subwork zone length and project start time, subject to queue length and travel delay constraints. Using average hourly traffic (AHT) data, this study shows that total user delay is non-differentiable with respect to the subwork zone length and project start time. This interesting finding demonstrates that previous analytic expressions of the optimal subwork zone length cannot hold for AHT data. To solve the proposed model, an enumeration method is designed. Finally, a numerical example created from the roadside tree trimming in Singapore is used to assess the model and solution method proposed in this study.
  Highlights ► The problem to determine optimal subwork zone length and project start time is proposed. ► A non-differentiable optimization model for the proposed problem is built. ► A numeration solution method for solving the non-differentiable model is designed.
  
  PubDate: 2013-02-28T10:10:58Z
Robust signal timing optimization with environmental concerns
- Abstract: April 2013
  Publication year: 2013
  Source:Transportation Research Part C: Emerging Technologies, Volume 29
  
  This paper formulates a bi-objective optimization model to determine timing plans for coordinated traffic signals along arterials to minimize traffic delay and the risk associated with human exposure to traffic emissions. Based on a cell-transmission representation of traffic dynamics, a modal sensitive emission approach is used to estimate the tailpipe emission rate for each cell of a signalized arterial. A cell-based Gaussian plume air dispersion model is then employed to capture the dispersion of air pollutants and compute the roadside pollutant concentrations. A measure of mean excess exposure is further defined to represent the risk associated with human exposure to traffic pollutants under the wind uncertainty. A signal timing optimization model is formulated to optimize the cycle length, offsets, green splits and phase sequences to minimize the total system delay and the mean excess exposure simultaneously. The bi-objective optimization model is solved via a simulation-based genetic algorithm to find a set of Pareto optimal solutions. A numerical example is presented to demonstrate the model.
  Highlights ► This paper develops a signal timing optimization model. ► The objective is to minimize both traffic delay and air pollutant concentrations. ► The model is macroscopic and computationally tractable. ► The model optimizes cycle length, green splits, phase sequences and offsets. ► A numerical example based on a real arterial is presented to demonstrate the model.
  
  PubDate: 2013-02-20T09:03:30Z
Evaluating ground–air network vulnerabilities in an integrated terminal maneuvering area using co-evolutionary computational red teaming
- Abstract: April 2013
  Publication year: 2013
  Source:Transportation Research Part C: Emerging Technologies, Volume 29
  
  The inherent complexity of a terminal maneuvering area (TMA) necessitates a system-level analysis to understand the overall system risk and vulnerabilities. The performance of advanced air traffic control (ATC) procedures, such as dynamic Continuous Descent Approaches (CDAs), may not be appropriately assessed without considering the complex interactions among other parts of the environment and the context in which they operate. The focus of this paper is a TMA system which integrates arrival and departure operations. It combines air and ground side resources to model and understand system-level vulnerabilities. We propose a methodology using the Computational Red Teaming (CRT) framework to identify ground–air network bottlenecks by exploring areas of vulnerability in the integrated TMA. The search engine in CRT relies on co-evolutionary search which evolves reciprocal interaction of traffic distributions and ground events (including runways, taxiways and gates). These interactions are modeled to identify inefficiencies resultant from the integration of arrival and departure operations. By evaluating these interactions, we are also able to identify “improvement opportunities” in the implementation of future air traffic management (ATM) concepts and, thereby, understand and work-around major bottlenecks which cause system inefficiencies. We illustrate the methodology on the Sydney Kingsford-Smith Airport’s domestic terminal area using a dynamic CDA scenario. Among our findings, taxiway B can cause significant delays if it is impacted by a ground event. In general, taxiways have been found to be a critical airport component with interactions between arrivals and departures, significantly impacting the airport’s throughput capacity.
  Highlights ► A co-evolutionary computational red teaming was developed. ► Different computational experiments were designed and implemented. ► The results showed that dynamic CDA can improve TMA system’s throughput capacity. ► Our analysis identified the bottlenecks of the integrated TMA system. ► Our analysis synthesize an overall situational awareness picture that decision makers can use.
  
  PubDate: 2013-02-20T09:03:30Z
Vehicular network sensor placement optimization under uncertainty
- Abstract: April 2013
  Publication year: 2013
  Source:Transportation Research Part C: Emerging Technologies, Volume 29
  
  Uncertainty is one of the major factors that transportation system analysts and planners have to deal with when making transportation planning decisions. Finding the set of optimal sensor locations under uncertainty is a network design problem. This paper presents a nonlinear two-stage stochastic model. The first stage provides a sensor location plan to maximize the origin–destination (OD) flow coverage and link information gains, subject to a budgetary limitation, before considering any random events, while the recourse function associated with the second stage calculates the expected cost of vehicular flow changes, after random events occur. This novel two-stage stochastic bi-objective model simultaneously maximizes a weighted combination of link information gains and OD flow coverage to locate network passive point sensors. An iterative heuristic solution algorithm, hybrid Greedy Randomized Adaptive Search Procedure (HGRASP), is developed to find the near-optimal locations for this problem. The proposed methodology is tested on the Coordinated Highways Action Response Team network (Washington DC–Baltimore, Maryland corridor), in a mesoscopic traffic simulator. The results confirm the expectations that, under stochastic conditions, the sensor location plans obtained under the assumption of stochastic conditions result in better performance than plans developed for deterministic (normal) conditions. Also as expected, a greater number of optimally deployed sensors reduces demand uncertainty for both normal and incident conditions.
  Highlights ► A two-stage stochastic formulation addresses network uncertainty in sensor location. ► It maximizes a weighted combination of link information gains and OD flow coverage. ► A hybrid Greedy Randomized Adaptive Search Procedure solves the problem. ► For stochastic conditions, sensor location plans for normal conditions are inferior. ► For such conditions, plans developed assuming stochastic conditions are superior.
  
  PubDate: 2013-02-16T09:03:46Z
Videoconferencing and business air travel: Do new technologies produce new interaction patterns'
- Abstract: April 2013
  Publication year: 2013
  Source:Transportation Research Part C: Emerging Technologies, Volume 29
  
  Videoconferencing is a technology in transit, with innovative platforms providing new communications opportunities and forms of co-operation. Although research has been occupied with the videoconferencing−business travel relationship for some time, little attention has been given to the diversity of the technology and how new technological platforms can create new interfaces with business travel. In this study, we summarize the emergence of videoconferencing as a business communication tool and emphasize the most recent developments. Data from a survey of business air passengers are used to examine access to different types of videoconferencing platforms and their interfaces with travel and face-to-face meetings. Results demonstrate an overall positive relationship between videoconferencing and business air travel, i.e., business people who travel a lot by air tend to participate in many video-meetings. However, the data also show large variations in travel and videoconferencing usage, and a substantial proportion of the respondents express a belief in travel replacement. Results from a regression analysis shows that respondents who have access to in-house videoconferencing rooms are more likely to believe in substitution than are those who only have available “new” technologies (e.g. videoconferencing for PC/Mac), even after controlling for individual and company characteristics.
  Highlights ► Small companies are more likely to utilize “new” videoconferencing platforms (e.g., web-based systems). ► Large variations in travel and videoconferencing usage is displayed. ► An overall positive relationship between videoconferencing and business air travel is revealed. ► Respondents beliefs in travel substitution is influenced by the type of videoconferencing technology available.
  
  PubDate: 2013-02-16T09:03:46Z