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  • 1. Ames, Alicia
    et al.
    Mateo-Babiano, Iderlina B.
    Susilo, Yusak O.
    KTH, School of Architecture and the Built Environment (ABE), Transport Science, Transport planning, economics and engineering.
    Transport Workers' Perspective on Indigenous Transport and Climate Change Adaptation2014In: Transportation Research Record, ISSN 0361-1981, E-ISSN 2169-4052, no 2451, p. 1-9Article in journal (Refereed)
    Abstract [en]

    This paper explores the potential role of indigenous transport for increasing the adaptive capacity of selected cities in developing Asia. Indigenous transport drivers were surveyed face-to-face in Bandung, Indonesia, and in Ho Chi Minh City, Vietnam, to gain an understanding of how transport workers, specifically drivers-operators, characterize transport modes considered as indigenous and perceive their potential role in increasing the adaptive capacity of these cities. The main finding was that indigenous transport modes in the two cities in the case study had evolved to fit a niche market influenced by differing urban scales and divergent demographic and geographic characteristics. Thus, the experiences and the perceptions of transport workers on indigenous transport were highly contextualized in relation to service and route characteristics. Operating conditions for drivers were indicative of the regulatory status of indigenous transport modes in the informal landscape. This analysis contributes to an increased understanding of the role and the operation of indigenous transport modes within the transport system. The analysis also contributes policy-relevant insights to improve an understanding of the potential role of indigenous transport in climate change adaptation, as well as to increase awareness and to anticipate a shift to a more environmentally sustainable transport mode.

  • 2.
    Andreasson, Ingmar J.
    KTH, School of Architecture and the Built Environment (ABE), Centres, Centre for Traffic Research, CTR.
    Personal Rapid Transit as Feeder-Distributor to Rail2012In: Transportation Research Record, ISSN 0361-1981, E-ISSN 2169-4052, no 2275, p. 88-93Article in journal (Refereed)
    Abstract [en]

    Efficient feeder distributor systems around train stations are important in attracting train passengers. Such systems would be a suitable application for personal rapid transit (PRT). This paper suggests layouts and operations strategies for transfer stations between PRT and heavy rail. Ticket handling can be avoided by having the train fare include PRT trips. Ridesharing can be encouraged by destination signs. The catchment area that can be efficiently served is related to the interval between trains. The capacity of the station and guideway can be improved by coupling PRT vehicles in the station and decoupling them as necessary en route. Applications in Sweden are illustrated with the PRTsim software. In one case, outgoing PRT vehicles were loaded to 78%.

  • 3. Antoniou, Constantinos
    et al.
    Ben-Akiva, Moshe
    Koutsopoulos, Haris N.
    KTH, School of Architecture and the Built Environment (ABE), Transport and Economics (closed 20110301).
    On-line Calibration of Traffic Prediction Models2005In: Transportation Research Record, ISSN 0361-1981, E-ISSN 2169-4052, Vol. 1934, p. 235-245Article in journal (Refereed)
    Abstract [en]

    A methodology for the on-line calibration of the speed-density relationship is formulated as a flexible state-space model. Applicable solution approaches are discussed and three of them (extended Kalman filter (EKF), iterated EKF, and unscented Kalman filter (UKF) are selected and presented in detail. An application of the methodology with freeway sensor data from two networks in Europe and the U.S. is presented. The improvement in the estimation and prediction of speeds due to on-line calibration (compared with the speeds obtained from the off-line calibrated relationship) is demonstrated. The EKF provides the most straightforward solution to this problem, and indeed achieves considerable improvements in estimation and prediction accuracy. The benefits obtained from the -more computationally expensive-iterated EKF algorithm are shown. An innovative solution technique (the UKF) is also presented. The UKF has a number of unique qualities and advantages over the EKF, including no assumption of analytical representation of the model and no need for explicit computation of derivatives. Empirical results suggest that the UKF outperforms the other two solution techniques in prediction accuracy.

  • 4. Antoniou, Constantinos
    et al.
    Koutsopoulos, Haris N.
    KTH, School of Architecture and the Built Environment (ABE), Transport and Economics (closed 20110301).
    Estimation of Traffic Dynamics Models with Machine Learning Methods2006In: Transportation Research Record, ISSN 0361-1981, E-ISSN 2169-4052, Vol. 1965, p. 103-111Article in journal (Refereed)
    Abstract [en]

    Speed-density relationships are a classic way of modeling stationary traffic relationships. Besides offering valuable insight into traffic stream flows, such relationships are widely used in dynamic traffic assignment (DTA) systems. In this research, an alternative paradigm for traffic dynamics models, appropriate for traffic simulation models and based on machine-learning approaches such as k-means clustering, k-nearest-neighborhood classification, and locally weighted regression is proposed. Although these models may not provide as much insight into traffic flow theory as speed-density relationships do, they allow for easy incorporation of additional information to speed estimation and hence may be more appropriate for use in DTA models, especially simulation-based models. This paper (with data from a network in Irvine, California) demonstrates that such machine-learning methods can considerably improve the accuracy of speed estimation.

  • 5.
    Balakrishna, R.
    et al.
    Caliper Corporation.
    Antoniou, C.
    Department of Transportation Planning and Engineering, National Technical University of Athens.
    Ben-Akiva, M.
    Massachusetts Institute of Technology.
    Koutsopoulos, Haris N.
    Northeastern University, Boston.
    Wen, Yang
    Massachusetts Institute of Technology.
    Calibration of Microscopic Traffic Simulation Models: Methods and Application2007In: Transportation Research Record, ISSN 0361-1981, E-ISSN 2169-4052, no 1999, p. 198-207Article in journal (Refereed)
    Abstract [en]

    A mathematical framework and a solution approach are presented for the simultaneous calibration of the demand and supply parameters and inputs to microscopic traffic simulation models as well as a large-scale application emphasizing practical issues. Microscopic traffic simulation models provide detailed estimates of evolving network conditions by modeling time-varying demand patterns and individual drivers' detailed behavioral decisions. Such models are composed of elements that simulate different demand and supply processes and their complex interactions. Several model inputs (such as origin-destination flows) and parameters (car-following and lane-changing coefficients) must be specified before these simulation tools can be applied, and their values must be determined so that the simulation output accurately replicates the reality reflected in traffic measurements. A methodology is presented here for simultaneously estimating all microscopic simulation model parameters by using general traffic measurements. A large-scale case study for the calibration of the MITSimLab microscopic traffic simulation model by using the network of Lower Westchester County, New York, is employed to demonstrate the feasibility, application, and benefits of the proposed methodology.

  • 6.
    Balakrishna, Ramachandran
    et al.
    Caliper Corp.
    Ben-Akiva, Moshe
    MIT, Cambridge.
    Koutsopoulos, Haris N.
    Northeastern Univ, Boston.
    Offline calibration of dynamic traffic assignment: Simultaneous Demand-and-Supply Estimation2007In: Transportation Research Record, ISSN 0361-1981, E-ISSN 2169-4052, no 2003, p. 50-58Article in journal (Refereed)
    Abstract [en]

    Advances in intelligent transportation systems have resulted in deployment of surveillance systems that automatically collect and store extensive networkwide traffic data. Dynamic traffic assignment (DTA) models have been developed for a variety of dynamic traffic management applications. They are designed to estimate and predict the evolution of congestion with detailed models and algorithms that capture travel demand and network supply and their complex interactions. The availability of rich time-varying traffic data spanning multiple days provides the opportunity to calibrate a DTA model’s inputs and parameters offline so that its outputs reflect field conditions in future offline and online real-time applications. The state of the art of DTA model calibration is a sequential approach, with supply model calibration (assuming known demand inputs) followed by demand calibration with fixed supply parameters. An offline DTA model calibration methodology is presented for simultaneous estimation of all demand-and-supply inputs and parameters, with sensor data. A minimization formulation that can use any general traffic data and present scalable solution approaches for the complex, nonlinear, stochastic optimization problem is adopted. A case study with DynaMIT, a DTA model with traffic estimation and prediction capabilities, is used to demonstrate and validate the methodology. Archived sensor data and a network from Los Angeles, California, are used to demonstrate scalability. Results indicate that the simultaneous approach significantly outperforms the sequential state of the art in terms of modeling accuracy and computational efficiency.

  • 7. Balakrishna, Ramachandran
    et al.
    Koutsopoulos, Haris N.
    KTH, School of Architecture and the Built Environment (ABE), Transport and Economics (closed 20110301), Traffic and Logistics (closed 20110301).
    Incorporating Within-Day Transitions in Simultaneous Offline Estimation of Dynamic Origin-Destination Flows Without Assignment Matrices2008In: Transportation Research Record, ISSN 0361-1981, E-ISSN 2169-4052, no 2085, p. 31-38Article in journal (Refereed)
    Abstract [en]

    An offline methodology is presented: it simultaneously estimates dynamic origin-destination (O-D) matrices, without using assignment matrices that incorporate within-day transition equations. The proposed formulation and solution approach extends a calibration method recently developed that directly uses the output of any network loading model (such as a dynamic traffic assignment or simulation model) so that the complex relationships between O-D flows and model outputs are accurately captured (as opposed to the more common method of approximate linear relationships based oil file assignment matrix). The study extends the original formulation by incorporating spatial and temporal relationships among various O-D flows (transition equations). These transition equations link O-D flow variables across time intervals in such it way that known structural demand patterns can be preserved in the new estimates. Such transition equations, although common in the context of real-time O-D flows, complicate the offline simultaneous estimation of O-D flows and have not been used to their full potential in the past. The approach is demonstrated through a case study.

  • 8.
    Balakrishna, Ramachandran
    et al.
    Department of Civil and Environmental Engineering, Massachusetts Institute of Technology.
    Koutsopoulos, Haris N.
    Department of Civil and Environmental Engineering, Northeastern University, Boston.
    Ben-Akiva, Moshe
    Department of Civil and Environmental Engineering, Northeastern University, Boston.
    Fernandez Ruiz, Bruno M.
    Massachusetts Institute of Technology.
    Mehta, Manish
    Lehman Brothers Inc..
    A Simulation-based Evaluation of Advanced Traveler Information Systems2005In: Transportation Research Record, ISSN 0361-1981, E-ISSN 2169-4052, Vol. 1910, p. 90-98Article in journal (Refereed)
    Abstract [en]

    Traveler information has the potential to reduce travel times and improve their reliability. Studies have verified that driver overreaction from the dissemination of information can be eliminated through prediction-based route guidance that uses short-term forecasts of network state. Critical off-line tests of advanced dynamic traffic assignment-based prediction systems have been limited, since the system being evaluated has also been used as the test bed. This paper outlines a detailed simulation-based laboratory for the objective and independent evaluation of advanced traveler information systems, a laboratory with the flexibility to analyze the impacts of various design parameters and modeling errors on the quality of the generated guidance. MITSIMLab, a system for the evaluation of advanced traffic management systems, is integrated with Dynamic Network Assignment for the Management of Information to Travelers (DynaMIT), a simulation-based decision support system designed to generate prediction-based route guidance. Evaluation criteria and requirements for the closed-loop integration of MITSIMLab and DynaMIT are discussed. Detailed case studies demonstrating the evaluation methodology and sensitivity of DynaMIT's guidance are presented.

  • 9. Bayarma, Alexander
    et al.
    Kitamura, Ryuichi
    Susilo, Yusak
    Delft University of Technology, Netherlands.
    On the recurrence of daily travel patterns: A stochastic-process approach to multi-day travel behavior2007In: Transportation Research Record, ISSN 0361-1981, E-ISSN 2169-4052, Vol. 2021, p. 55-63Article in journal (Refereed)
    Abstract [en]

    Multiday travel behavior was examined as a stochastic process, and new empirical findings are offered on the variation of travel patterns from day to day. The analysis was based on data from a 6-week travel diary survey conducted in Germany. A small number of travel pattern classes were identified, and transitions in the patterns over a course of weeks were analyzed with Markov chain models. Transitions from a pattern to itself are frequent, particularly for nonworkers, and indicate that some patterns tend to be pursued for a large number of consecutive days. The study also reveals that individuals are heterogeneous in terms of multiday travel behavior; pattern-to-pattern transition probabilities vary substantially across individuals. Some of the observable heterogeneity is demonstrated in terms of the association between attributes of the individual and the recurrence of daily travel patterns.

  • 10.
    Bierlaire, Michel
    et al.
    Transport and Mobility Laboratory, Ecole Polytechnique Federale de Lausanne.
    Flötteröd, Gunnar
    Transport and Mobility Laboratory, Ecole Polytechnique Fédérale de Lausanne.
    An analysis of the implicit choice set generation using the constrained multinomial logit model2010In: Transportation Research Record, ISSN 0361-1981, E-ISSN 2169-4052, Vol. 2175, p. 92-97Article in journal (Refereed)
    Abstract [en]

    Discrete choice models are defined conditional to the analyst's knowledge of the actual choice set. The common practice for many years has been to assume that individual-based choice sets can be deterministically generated on the basis of the choice context and characteristics of the decision maker. This assumption is not valid or not applicable in many situations, and probabilistic choice set formation procedures must be considered. The constrained multinomial logit model (CMNL) has recently been proposed as a convenient way to deal with this issue, as it is also appropriate for models with a large choice set. In this paper, how well the implicit choice set generation of the CMNL approximates the explicit choice set generation is analyzed as described in earlier research. The results based on synthetic data show that the implicit choice set generation model may be a poor approximation of the explicit model

  • 11.
    Birgisson, Björn
    KTH, School of Architecture and the Built Environment (ABE), Civil and Architectural Engineering, Highway and Railway Engineering (closed 20110301).
    Nanotechnology in Cement and Concrete VOLUME 2 Foreword2010In: Transportation Research Record, ISSN 0361-1981, E-ISSN 2169-4052, no 2142, p. IX-XArticle in journal (Other academic)
  • 12.
    Birgisson, Björn
    et al.
    University of Florida.
    Roque, R.
    Evaluation of Gradation Effects on Dynamic Modulus2005In: Transportation Research Record, ISSN 0361-1981, E-ISSN 2169-4052, no 1929, p. 193-199Article in journal (Refereed)
    Abstract [en]

    The importance of aggregate characteristics has been emphasized in the Superpave (R) asphalt mixture design procedure. However, criteria for guidelines for the selection of suitable aggregate gradations-other than gradation limits for different nominal maximum size aggregate blends, including the restricted zone-have been neglected. With the move toward mechanistic-empirical pavement design, the dynamic modulus is used to account for mixture properties in the pavement design. It is of significant importance to mix designers to possess a framework for determining how to optimize a mixture for ensuring an adequate dynamic modulus. This paper presents the results from a study of the effects of gradation characteristics on the dynamic modulus. Power law-based gradation factors are obtained for 13 aggregate gradations (coarse and fine graded) composed of limestone and granite aggregates. These gradation factors were used to identify and evaluate relationships between gradation factors and the dynamic modulus at higher temperature (40 degrees C). Subsequently, a tentative framework was established for optimizing mixture gradations for dynamic modulus values. Findings illustrate that gradation factors based on power law parameters can be used to optimize mixture gradations for key mixture properties, such as the dynamic modulus. Results also demonstrate the critical nature of aggregate gradation in achieving desired mixture properties.

  • 13.
    Birgisson, Björn
    et al.
    University of Florida.
    Roque, R.
    Page, G.
    Performance-based fracture criterion for evaluation of moisture susceptibility in hot-mix asphalt2004In: Transportation Research Record, ISSN 0361-1981, E-ISSN 2169-4052, no 1891, p. 55-61Article in journal (Refereed)
    Abstract [en]

    The laboratory testing procedures currently available for testing hot-mix asphalt moisture susceptibility all evaluate the effects of moisture damage in the laboratory by measuring the relative change of a single parameter before and after conditioning (i.e., tensile strength ratio, resilient modulus ratio). The use of a single parameter to evaluate moisture damage must be questioned. Instead, a single unified framework that accounts for changes in key mixture properties is needed to evaluate the effects of moisture damage in mixtures effectively. The use of a new performance-based fracture parameter, the energy ratio (ER), for quantifying the effects of moisture damage on the fracture resistance of mixtures is evaluated here. ER is used to determine the effects of moisture damage on changes in the fracture resistance of six granite mixtures prepared with and without the use of an antistripping additive. The granite aggregate used is a known stripping aggregate. In addition, one limestone mixture with a known high resistance to stripping was used. The results indicate that not only is the ER capable of detecting the effects of moisture damage on the fracture resistance of mixtures, it is also shown to detect the presence of antistripping agents in mixtures. Results indicate that the ER may form the basis of a promising combined performance-based fracture criterion for evaluating the effects of moisture damage in mixtures as well as the overall resistance to fracture.

  • 14. Birgisson, Björn
    et al.
    Roque, Reynaldo
    Page, Gale C.
    Wang, Jianlin
    Development of new moisture-conditioning procedure for hot-mix asphalt2007In: Transportation Research Record, ISSN 0361-1981, E-ISSN 2169-4052, no 2001, p. 46-55Article in journal (Refereed)
    Abstract [en]

    The presence of pore water in mixtures can cause premature failure of hot-mix asphalt pavements. The processes typically associated with moisture damage are complex and occur over a long period of time in the field. Short of being able to simulate each of the possible mechanisms of moisture damage directly, the ideal laboratory-based conditioning system should accelerate the penetration of moisture through the asphalt film and at the same time minimize complicating effects. This paper presents the results of an experiment conducted to determine whether it was possible to use cyclic pore pressures to induce enough damage to distinguish between mixtures known to be highly resistant from mixtures known to be susceptible to moisture damage. Experimental constraints included requirements that conditioning be accomplished within a reasonable length of time and that typical laboratory equipment be used. Evaluation of the resulting effects of moisture damage included the use of the Superpave (R) indirect tension test and the energy ratio parameter. Findings show that cyclic pore pressures can be used to accelerate moisture damage enough to distinguish between mixtures known to be strippers and those known to be highly resistant to moisture damage. The use of cyclic pore pressures to accelerate moisture damage in mixtures may minimize the introduction of other confounding damage effects on the mixtures.

  • 15. Birgisson, Björn
    et al.
    Sholar, G.
    Roque, R.
    Evaluation of a predicted dynamic modulus for Florida mixtures2005In: Transportation Research Record, ISSN 0361-1981, E-ISSN 2169-4052, no 1929, p. 200-207Article in journal (Refereed)
    Abstract [en]

    The new 2002 AASHTO guide for the design of pavement structures is based on mechanistic principles and requires the dynamic modulus as input to compute stress, strain, and rutting and cracking damage in flexible pavements. The 2002 AASHTO guide has three different levels of analysis; the level used depends on the importance of the pavement structure in question. Dynamic modulus testing is required for Level 1 pavement analysis, whereas no laboratory test data are required for Level 2 and Level 3 pavement analysis. Instead, a predictive dynamic modulus equation is used to generate input values. It is of significant importance to state agencies to understand how well the dynamic modulus for locally available materials compares with the predicted dynamic modulus. This paper presents the results of a study by the Florida Department of Transportation and the University of Florida that focused on the evaluation of the dynamic modulus predictive equation used in the new AASHTO 2002 guide for mixtures typical to Florida. The resulting research program consisted of dynamic modulus testing of 28 mixtures common to Florida. Results showed that on average the predictive modulus equation used in the new AASHTO 2002 flexible pavement design guide appeared to work well for Florida mixtures when used with a multiptier to account for the uniqueness of local mixtures. Results of the study also identified optimal viscosity-temperature relationships that result in the closest correspondence between measured and predicted dynamic modulus values.

  • 16.
    Birgisson, Björn
    et al.
    KTH, School of Architecture and the Built Environment (ABE), Civil and Architectural Engineering, Highway and Railway Engineering.
    Taylor, Peter
    Armaghani, Jamshid
    Shah, Surendra P.
    American Road Map for Research for Nanotechnology-Based Concrete Materials2010In: Transportation Research Record, ISSN 0361-1981, E-ISSN 2169-4052, no 2142, p. 130-137Article in journal (Refereed)
    Abstract [en]

    The mechanical behavior of concrete materials depends to a large extent on structural elements and phenomena that are effective on micro- and nanoscales. The nanomodification of concrete materials has the potential to open up new uses and classes of concrete materials, with wide-ranging implications for the concrete transportation infrastructure. The development of nanotechnology-based concrete materials will require a multidisciplinary approach, consisting of teams of civil engineers, chemists, physicists, and materials scientists. To help develop nanotechnology-based concrete materials, a concentrated effort was undertaken in the United States to develop a national road map for research in this area. This effort included two National Science Foundation (NSF) workshops held in August 2006 and September 2007. In addition to NSF, the Portland Cement Association, the Defense Threat Reduction Agency, the Florida Concrete and Products Association, the Army Corps of Engineers, TRB, and the International Union of Testing and Research Laboratories for Materials and Structures sponsored this effort. The road map for nanotechnology-based concrete materials charts a path beginning with current nanotechnology capabilities to advanced materials and systems. The road map details key milestones and step-by-step short-term, intermediate, and long-term courses of development that must take place to reach these key milestones. The road map also serves as a tool to identify the gap between the basic concrete materials of today and the potential of nanosystems and nanomaterials interacting in concrete nano-houses, nano-bridges, and nano-pavements. The national road map for nanotechnology-based concrete is described and discussed.

  • 17.
    Burghout, Wilco
    et al.
    KTH, School of Architecture and the Built Environment (ABE), Transport and Economics.
    Koutsopoulos, Haris N.
    KTH, School of Architecture and the Built Environment (ABE), Transport and Economics.
    Andreasson, Ingmar
    KTH, School of Architecture and the Built Environment (ABE), Transport and Economics.
    Hybrid Mesoscopic-Microscopic Traffic Simulation2005In: Transportation Research Record, ISSN 0361-1981, E-ISSN 2169-4052, Vol. 1934, p. 218-225Article in journal (Refereed)
    Abstract [en]

    Traffic simulation is an important tool for modeling the operations of dynamic traffic systems. Although microscopic simulation models provide a detailed representation of the traffic process, macroscopic and mesoscopic models capture the traffic dynamics of large networks in less detail but without the problems of application and calibration of microscopic models. This paper presents a hybrid mesoscopic-microscopic model that applies microscopic simulation to areas of specific interest while simulating a large surrounding network in less detail with a mesoscopic model. The requirements that are important for a hybrid model to be consistent across the models at different levels of detail are identified. These requirements vary from the network and route choice consistency to the consistency of the traffic dynamics at the boundaries of the microscopic and mesoscopic submodels. An integration framework that satisfies these requirements is proposed. A prototype hybrid model is used to demonstrate the application of the integration framework and the solution of the various integration issues. The hybrid model integrates MlTSIMLab, a microscopic traffic simulation model, and Mezzo, a newly developed mesoscopic model. The hybrid model is applied in two case studies. The results are promising and support both the proposed architecture and the importance of integrating microscopic and mesoscopic models.

  • 18.
    Burghout, Wilco
    et al.
    KTH, School of Architecture and the Built Environment (ABE), Transport and Economics.
    Koutsopoulos, Haris N.
    KTH, School of Architecture and the Built Environment (ABE), Transport and Economics, Traffic and Logistics.
    Andreasson, Ingmar
    KTH, School of Architecture and the Built Environment (ABE), Transport and Economics.
    Incident Management and Traffic Information Tools and Methods for Simulation-Based Traffic Prediction2010In: Transportation Research Record, ISSN 0361-1981, E-ISSN 2169-4052, no 2161, p. 20-28Article in journal (Refereed)
    Abstract [en]

    Incident response and mitigation are among the main tasks of operators at traffic control centers. Simulation models have a good chance of reproducing and predicting the effects of incident response by explicitly modeling driver response to the incident and information provided. In the PREDIKT project sponsored by the Swedish National Road Administration, the state-of-the-art mesoscopic simulation model MEZZO was extended to provide decision support for incident management. Numerous essential modeling components are described and tested, including modeling the incident response logic, a mixed-logit model, and a method for generating alternatives for drivers switching routes. In addition, the results of a fast calibration method based on simultaneous perturbation statistic approximation are presented. The model components are tested in a small case study that investigates the effect of delay in providing information to drivers after incidents. A linearization of speed-density functions also is shown to improve computational performance by 30% and increase calibration speed and stability while preserving simulation accuracy.

  • 19.
    Burghout, Wilco
    et al.
    KTH, School of Architecture and the Built Environment (ABE), Transport and Economics (closed 20110301).
    Wahstedt, Johan
    Hybrid traffic simulation with adaptive signal control2007In: Transportation Research Record, ISSN 0361-1981, E-ISSN 2169-4052, no 1999, p. 191-197Article in journal (Refereed)
    Abstract [en]

    A hybrid mesoscopic-microscopic model is implemented that applies microscopic simulation to areas of specific interest while simulating a large surrounding network in lesser detail with a mesoscopic model. The hybrid model integrates VisSim, a microscopic traffic simulation model, and Mezzo, a recently developed mesoscopic model. The hybrid model is applied on a network in which Mezzo simulates the entire area (6,000 links) of Stockholm, Sweden, and VisSim simulates the area of specific interest, containing three intersections with adaptive signal control with bus-priority functions. The adaptive signal control and bus-priority functions are simulated by a separate signal controller simulator (EC-1 simulator) that interacts with the hybrid Mezzo-VisSim model and thereby provides the actual signal changes that would take place in the field. Two alternative control schemes are evaluated with the hybrid setup: the original fixed-time control and the new adaptive control. The results show clear improvement in terms of travel times, delays, and stops with the new adaptive control scheme. They also show that although these improvements for the local (microlevel) area attract additional traffic from the surrounding (mesolevel) area, the net effects both locally and networkwide remain positive in terms of travel times, average number of stops, and delay. Moreover, this study demonstrates the advantages of hybrid simulation in evaluation of complicated adaptive traffic control in which both local detailed effects and network effects need to be studied.

  • 20.
    Börjesson, Maria
    et al.
    KTH, School of Architecture and the Built Environment (ABE), Centres, Centre for Transport Studies, CTS.
    Cherchi, Elisabetta
    Bierlaire, Michel
    Within-Individual Variation in Preferences Equity Effects of Congestion Charges2013In: Transportation Research Record, ISSN 0361-1981, E-ISSN 2169-4052, no 2382, p. 92-101Article in journal (Refereed)
    Abstract [en]

    The purpose of this research was to explore how the values of travel time (VTT) and preferences for different modes vary within individuals compared with the variation between observed trips. With 6-week revealed preference panel data and stated preference data from a mode choice context, both collected in Switzerland, a revealed stated preference logit mode choice model was estimated. The model was applied to simulate how VTT and change in consumer surplus vary across trips within and between individuals over the 6 weeks in response to a hypothetical congestion-charging scheme. The variation in VTT arising from income differences was found to be substantially smaller than the variation in VTT between trips. Moreover, the variability in VTT averaged over all trips within each individual was considerably smaller than the variability in VTT for all observed trips. Therefore, the assumption that variation in VTT between observed trips reflects the variation in the average VTT between individuals, which is usually made in equity analyses, will over-state the between-individual variation. The results suggest that if intraindividual variation in preferences is not taken into account, the negative equity effects of congestion charges are likely to be overestimated.

  • 21.
    Cats, Oded
    et al.
    Delft University, Netherlands.
    Abenoza, Roberto
    KTH, School of Architecture and the Built Environment (ABE), Transport Science, Transport Planning, Economics and Engineering.
    Liu, Chengxi
    KTH, School of Architecture and the Built Environment (ABE), Transport Science, Transport Planning, Economics and Engineering.
    Susilo, Yusak
    KTH, School of Architecture and the Built Environment (ABE), Transport Science, Transport Planning, Economics and Engineering.
    Evolution of Satisfaction with Public Transport and Its Determinants in Sweden Identifying Priority Areas2015In: Transportation Research Record, ISSN 0361-1981, E-ISSN 2169-4052, no 2538, p. 86-95Article in journal (Refereed)
    Abstract [en]

    Measuring and analysing satisfaction with public transport services facilitates service performance monitoring, market analysis, benchmarking and the identification of priority areas. The systematic and regular collection of information concerning satisfaction enables to investigate how passengers’ satisfaction as well as its determinants changes over time. These changes may be driven by changes in service quality or shifts in passengers’ expectations and preferences. This study analyses how satisfaction with public transport and its determinants evolved over time in Sweden in the years 2001-2013. The determinants of satisfaction are identified based on a factor analysis and the estimation of multivariate satisfaction models. The superposition of our findings culminates in a dynamic passenger satisfaction priority map which allows identifying priority areas based on observed trends in satisfaction with service attributes and their respective importance. The deterioration of overall satisfaction with public transport in Sweden in recent years is driven by a decrease in satisfaction with customer interface and length of trip time. These two service aspects as well as operation were found key determinants of overall satisfaction which users consistently rate among the least satisfactory. The results of this study are instrumental in supporting service providers in designing measures that will foster satisfaction in the future.

  • 22.
    Cats, Oded
    et al.
    Faculty of Civil and Environmental Engineering, Technion-Israel Institute of Technology, Haifa.
    Burghout, Wilco
    KTH, School of Architecture and the Built Environment (ABE), Transport and Economics (closed 20110301), Traffic and Logistics (closed 20110301). KTH, School of Architecture and the Built Environment (ABE), Centres, Centre for Traffic Research, CTR.
    Toledo, Tomer
    Koutsopoulos, Harilaos
    KTH, School of Architecture and the Built Environment (ABE), Transport and Economics (closed 20110301), Traffic and Logistics (closed 20110301).
    Mesoscopic Modeling of Bus Public Transportation2010In: Transportation Research Record, ISSN 0361-1981, E-ISSN 2169-4052, no 2188, p. 9-18Article in journal (Refereed)
    Abstract [en]

    Analysis of public transport system performance and level of service in urban areas is essential. Dynamic modeling of traffic conditions, passenger demand, and transit operations is important to represent adequately the complexity of and the interactions between these components in modern public transportation systems. This paper presents a transit simulation model designed to support evaluation of operations planning and control, especially in the context of advanced public transportation systems. Unlike most previous efforts in this area, the simulation model is built on a platform of a mesoscopic traffic simulation model, which allows modeling or the operation dynamics of large-scale transit systems, taking into account the main sources of service uncertainty and stochasticity. The capabilities of Mezzo as an evaluation tool of transit operations are demonstrated with an application to a real-world, high-demand bus line in metropolitan Tel Aviv, Israel, under various scenarios. The application shows that important phenomena such as bus bunching are reproduced realistically. A comparison of simulated running times and headway distributions with field data shows the model is capable of replicating observed data.

  • 23.
    Cats, Oded
    et al.
    KTH, School of Architecture and the Built Environment (ABE), Transport Science, Traffic and Logistics.
    Koutsopoulos, Haris
    KTH, School of Architecture and the Built Environment (ABE), Transport Science, Traffic and Logistics.
    Burghout, Wilco
    KTH, School of Architecture and the Built Environment (ABE), Centres, Centre for Traffic Research, CTR. KTH, School of Architecture and the Built Environment (ABE), Transport Science, Traffic and Logistics.
    Toledo, Tomer
    Evaluating the role of real-time transit information provision on dynamic passenger path choice2012In: Transportation Research Record, ISSN 0361-1981, E-ISSN 2169-4052Article in journal (Refereed)
  • 24.
    Cats, Oded
    et al.
    KTH, School of Architecture and the Built Environment (ABE), Transport Science, Traffic and Logistics. KTH, School of Architecture and the Built Environment (ABE), Centres, Centre for Traffic Research, CTR.
    Larijani, Anahid
    KTH, School of Architecture and the Built Environment (ABE), Transport Science, Traffic and Logistics.
    Koutsopoulos, Haris
    KTH, School of Architecture and the Built Environment (ABE), Transport Science, Traffic and Logistics.
    Burghout, Wilco
    KTH, School of Architecture and the Built Environment (ABE), Transport Science, Traffic and Logistics. KTH, School of Architecture and the Built Environment (ABE), Centres, Centre for Traffic Research, CTR.
    Impacts of holding control strategies on transit performance: A bus simulation model analysis2011In: Transportation Research Record, ISSN 0361-1981, E-ISSN 2169-4052, no 2216, p. 51-58Article in journal (Refereed)
    Abstract [en]

    Transit operators are interested in strategies to improve service reliability as it is an important measure of performance and level of service. One of the common practices aimed at reducing service unreliability is holding control strategies. The design of these strategies involves the selection of a set of time point stops and the holding criteria for regulating the departure time. The interactions between passenger activity, transit operations, and traffic dynamics must be dynamically modeled to analyze the impacts of holding strategies on transit performance. An evaluation of different holding criteria and the number and location of time point stops was conducted with Bus Mezzo, a dynamic transit simulation model. The holding strategies were implemented in the model and applied to a high-frequency trunk bus line in Stockholm, Sweden. The analysis of the results considers the implications of holding strategies from both passenger and operator perspectives. The analysis suggests substantial gains are possible by implementing a holding strategy on the basis of the mean headway from the preceding and the succeeding buses. This strategy is the most efficient for passenger time savings as well as fleet costs and crew management.

  • 25.
    Cats, Oded
    et al.
    KTH, School of Architecture and the Built Environment (ABE), Centres, Centre for Traffic Research, CTR.
    Larijani, Anahid Nabavi
    KTH, School of Architecture and the Built Environment (ABE), Transport Science, Traffic and Logistics.
    Ólafsdóttir, Ásdís
    KTH, School of Architecture and the Built Environment (ABE), Transport Science, Traffic and Logistics.
    Burghout, Wilco
    KTH, School of Architecture and the Built Environment (ABE), Centres, Centre for Traffic Research, CTR.
    Andréasson, Ingmar J.
    KTH, School of Architecture and the Built Environment (ABE), Centres, Centre for Traffic Research, CTR.
    Koutsopoulos, Harilaos N.
    KTH, School of Architecture and the Built Environment (ABE), Transport Science, Traffic and Logistics.
    Bus-Holding Control Strategies Simulation-Based Evaluation and Guidelines for Implementation2012In: Transportation Research Record, ISSN 0361-1981, E-ISSN 2169-4052, no 2274, p. 100-108Article in journal (Refereed)
    Abstract [en]

    Transit operations involve several inherent sources of uncertainty, including dispatch time from the origin terminal, travel time between stops, and dwell time at stops. Bus-holding control strategies are a prominent method applied by transit operators to improve transit performance and level of service. The common practice is to regulate departures from a limited number of stops by holding buses until their scheduled departure time. An analysis of the performance of a high-frequency bus line in Stockholm, Sweden, based on automatic vehicle location data showed that this control strategy was not effective in improving service regularity along the line. The analysis also indicated that drivers adjusted their speed according to performance objectives. Implications of a control strategy that regulates departures from all stops on the basis of the headways of the preceding bus and the following bus were evaluated with Bus Mezzo, a transit operations simulation model. The results suggest that this strategy can improve service performance considerably from both passengers' and operator's perspectives. In addition, the strategy implies cooperative operations, as the decisions of each driver are interdependent with other drivers' decisions, and mutual corrections can be made. Difficulties in realizing the benefits of the proposed strategy in practice, such as dispatching from the origin terminal, driver scheduling, and compliance, are discussed. The implications of several practical considerations are assessed by conducting a sensitivity analysis as part of the preparations for a field experiment designed to test the proposed control strategy.

  • 26.
    Cats, Oded
    et al.
    KTH, School of Architecture and the Built Environment (ABE), Transport Science, Traffic and Logistics. KTH, School of Architecture and the Built Environment (ABE), Centres, Centre for Traffic Research, CTR.
    Reimal, Triin
    KTH, School of Architecture and the Built Environment (ABE), Centres, Centre for Traffic Research, CTR.
    Susilo, Yusak
    KTH, School of Architecture and the Built Environment (ABE), Transport Science, Transport and Location Analysis. KTH, School of Architecture and the Built Environment (ABE), Centres, Centre for Traffic Research, CTR.
    Public Transport Pricing Policy Empirical Evidence from a Fare-Free Scheme in Tallinn, Estonia2014In: Transportation Research Record, ISSN 0361-1981, E-ISSN 2169-4052, no 2415, p. 89-96Article in journal (Refereed)
    Abstract [en]

    Cities worldwide are looking for new policies to attract travelers to shift from cars to public transport. Policies focused on reducing public transport fares are aimed at improving social inclusion and leading to a modal shift. The City of Tallinn, the capital of Estonia, has recently introduced a fare-free public transport (FFPT) service in an effort to improve accessibility and mobility for its residents. The case of Tallinn is a full-scale, real-world experiment that provides a unique opportunity for investigating the impacts of FFPT policy. A macrolevel empirical evaluation of FFPT impacts on service performance, passenger demand, and accessibility for various groups of travelers is presented. In contrast to previous studies, the influence of FFPT on passenger demand was estimated while changes in supply were controlled. The results indicate that the FFPT measure accounts for an increase of 1.2% in passenger demand, with the remaining increase attributed to an extended network of public transport priority lanes and increased service frequency. The relatively small effect could be attributed to the previous price level and public transport share as well as analysis of the short-term impact. The evidence-based policy evaluation in this paper is instrumental in supporting policy making and facilitating the design of public transport pricing strategies.

  • 27.
    Chen, Feng
    et al.
    KTH, School of Architecture and the Built Environment (ABE), Civil and Architectural Engineering.
    Balieu, Romain
    KTH, School of Architecture and the Built Environment (ABE), Civil and Architectural Engineering, Structural Engineering and Bridges.
    Kringos, Nicole
    KTH, School of Architecture and the Built Environment (ABE), Civil and Architectural Engineering, Structural Engineering and Bridges.
    Potential Influences on Long-Term Service Performance of Road Infrastructure by Automated Vehicles2016In: Transportation Research Record, ISSN 0361-1981, E-ISSN 2169-4052, no 2550, p. 72-79Article in journal (Refereed)
    Abstract [en]

    Automated vehicles (AVs) have received great attention in recent years, and an automated road transportation sector may become reality in the next decades. Many benefits of AVs have been optimistically predicted, although some benefits may be overestimated because of a lack of thinking from a holistic point of view. From a future perspective, this study investigated the potential consequences to the long-term service performance of practical physical road infrastructure after the advent of the implementation of AVs on a large scale. Specifically, the, pavement rutting performance by the possibly changed behaviors, such as the vehicle's wheel wander, lane capacity, and traffic speed, was examined carefully with the finite element modeling approach. With the use of AVs, the decreased wheel wander and increased lane capacity could bring an accelerated rutting potential, but the increase in traffic speed would negate this effect, which was shown by the simulation results of rut depth. Therefore the influence cannot be judged as positive or negative in general; judgment actually depends much on the practical road and traffic conditions. In the future the physical roads not only might serve for the mobility of the vehicles but also might be capable of enabling other new functions. An early consideration of how to lead the future development of physical road infrastructure toward multifunctionality is emphasized.

  • 28. Chen, M.
    et al.
    Wang, D.
    Sun, Y.
    Liu, Chengxi
    KTH, School of Architecture and the Built Environment (ABE), Transport Science, Transport Planning, Economics and Engineering.
    Bai, Z.
    Service evaluation of public bicycle scheme from a user perspective2017In: Transportation Research Record, ISSN 0361-1981, E-ISSN 2169-4052, Vol. 2634, p. 28-34Article in journal (Refereed)
    Abstract [en]

    In late 2005, in an attempt to solve the last-mile problem, China started implementing public bikesharing programs. The effort quickly grew to a massive scale. An estimated 400,000 public bicycles now are in use in China, which is more than in all other countries that have implemented public bicycle schemes (PBSs). As with any emerging service that develops rapidly, an understanding of user behavior and satisfaction is lacking. Factors that influence the frequency of public bicycle use were studied in Hangzhou, China. Online and intercept surveys were conducted with PBS users. Willingness to use the PBS as well as satisfaction with and concerns about the PBS were investigated. Analysis of variance was conducted to identify the six factors that affect a user's decision to rent: car ownership, bicycle ownership, travel purpose, having or lacking familiarity with the rental process, level of satisfaction with the PBS, and level of familiarity with the distribution of docking stations. Binary logistic regression analysis was used to elucidate details of key factors in the group of most frequent users-that is, survey respondents who did not own a car, rented a bicycle primarily for shopping or going out for business, and were familiar with the rental process and the distribution of docking stations. Based on study findings, advice is presented for implementing policy in developing countries. Suggestions include publicizing the PBS more, attracting more commuters to bicycling to reduce congestion, enhancing the accessibility of docking stations to accommodate more potential users, and improving bicycle quality to encourage more participation and make it easier for elderly citizens to participate.

  • 29.
    Dinegdae, Yared H.
    et al.
    KTH, School of Architecture and the Built Environment (ABE), Civil and Architectural Engineering.
    Birgisson, Björn
    Aston Univ..
    Reliability-Based Design Procedure for Fatigue Cracking in Asphalt Pavements2016In: Transportation Research Record, ISSN 0361-1981, E-ISSN 2169-4052, no 2583, p. 127-133Article in journal (Refereed)
    Abstract [en]

    The need to account for the effect of design input variabilities on predicted performance has led to many design procedures that address reliability for pavement applications. The Florida cracking model uses empirically derived reliability for fatigue cracking design of asphalt pavements. A reliability approach, which is based on probabilistic uncertainty quantification, is necessary to account properly and effectively for the contribution of the variability in each parameter to the overall variance. This paper presents a load and resistance factor design (LRFD) procedure for the Florida cracking model. By delivering designs of uniform reliability, LRFD provides the basis for developing quality control and quality assurance standards. A first-order reliability method that incorporates a surrogate model based on central composite design was used to compute the reliability and formulate the partial safety factors. The reliability calibration was based on field pavement sections that had a wide range of design inputs and target reliability. Illustrative designs based on the developed LRFD procedure show the effectiveness of the partial safety factors and further confirm the credibility of the reliability analysis methodology.

  • 30. Ding, Jing
    et al.
    Gao, Song
    Jenelius, Erik
    KTH, School of Architecture and the Built Environment (ABE), Transport Science.
    Rahmani, Mahmood
    KTH, School of Architecture and the Built Environment (ABE), Transport Science.
    Huang, He
    Ma, Long
    Pereira, Francisco
    Ben-Akiva, Moshe
    Routing Policy Choice Set Generation in Stochastic Time-Dependent Networks Case Studies for Stockholm, Sweden, and Singapore2014In: Transportation Research Record, ISSN 0361-1981, E-ISSN 2169-4052, no 2466, p. 76-86Article in journal (Refereed)
    Abstract [en]

    Transportation systems are inherently uncertain because of random disruptions; nevertheless, real-time information can help travelers make better route choices under such disruptions. The first revealed-preference study of routing policy choice is presented. A "routing policy" is defined as a decision rule applied at each link that maps possible realized traffic conditions to decisions to be made on the link next. The policy represents a traveler's ability to incorporate real-time information not yet available at the time of decision. Two case studies are conducted in Stockholm, Sweden, and in Singapore. Data for the underlying stochastic time-dependent network are generated from taxi GPS traces through map-matching and nonparametric link travel time estimation. An efficient algorithm to find the optimal touting policy in large-scale networks is first presented, which is a building block of any routing policy choice set generation method. The routing policy choice sets are then generated by link elimination and simulation. The generated choice sets are first evaluated on the basis of whether they include the observed traces on a specific day, or coverage. The sets are then evaluated on the basis of "adaptiveness," defined as the capability of a routing policy to be realized as different paths over different days. A combination of link elimination and simulation methods yields satisfactory coverage. The comparison with a path choice set benchmark also suggests that a routing policy choice set could potentially provide better coverage and capture the adaptive nature of route choice.

  • 31.
    Engelson, Leonid
    KTH, School of Architecture and the Built Environment (ABE), Transport Science, Transport and Location Analysis. KTH, School of Architecture and the Built Environment (ABE), Centres, Centre for Transport Studies, CTS.
    Properties of Expected Travel Cost Function with Uncertain Travel Time2011In: Transportation Research Record, ISSN 0361-1981, E-ISSN 2169-4052, no 2254, p. 151-159Article in journal (Refereed)
    Abstract [en]

    The paper presents a theoretical analysis of travelers' scheduling preferences and the resulting form of the expected utility that includes travel time reliability measures. A series of research papers and reports used the mean standard deviation approach to evaluate policies that improve travel time reliability. Recently, this approach was theoretically substantiated under the conventional assumptions of constant marginal utility of time (MUT) at the origin, two discrete MUT values at the destination, and constant standardized travel time distribution. In this paper, properties of the minimal expected travel cost are investigated with smooth MUTs at the origin and destination of the trip. The influence of small variations in travel time on travel cost is well approximated by a term proportional to the travel time variance and independent of the distribution form of travel time. Two examples of MUT functions are provided: the minimal expected travel cost can be analytically expressed through moments or through a moment generating function of travel time, and conditions are stated guaranteeing that the expected travel cost is exactly additive by independent parts of the trip. These results provide justification in particular for the mean variance approach to modeling drivers' decisions under uncertain travel times. This formulation is convenient especially for scheme evaluation in large road networks because it allows the use of conventional network assignment routines by just modifying the volume delay functions to include the travel time variability term.

  • 32.
    Erlingsson, Sigurdur
    et al.
    KTH, School of Architecture and the Built Environment (ABE), Transport Science, Highway and Railway Engineering.
    Rahman, Mohammad Shafiqur
    KTH, School of Architecture and the Built Environment (ABE), Transport Science, Highway and Railway Engineering.
    Evaluation of Permanent Deformation Characteristics of Unbound Granular Materials by Means of Multistage Repeated-Load Triaxial Tests2013In: Transportation Research Record, ISSN 0361-1981, E-ISSN 2169-4052, no 2369, p. 11-19Article in journal (Refereed)
    Abstract [en]

    Rutting in flexible pavements is often associated with permanent deformation of the unbound granular layer. The current permanent deformation models are applicable only to a single stress path in repeated-load triaxial (RLT) tests, in which the load pulses are of constant amplitude. In this paper, a general approach using the time-hardening concept was introduced to model the permanent deformation of unbound granular materials (UGMs) continuously in multistage (MS) RLT tests, in which load pulses of a range of different amplitudes are applied, to represent field conditions realistically. With this formulation, three existing permanent deformation models were reconstructed, and one of the models was slightly modified, to suit MS loading conditions better. The material parameters of these models were then optimized for three UGMs used in pavement construction with data from MS RLT tests and application of a least squares curve-fitting method to the test data. The goodness-of-fit statistics were computed to evaluate and compare the quality of fit achieved with these models. The shakedown ranges were also calculated for each stress path of the MS RLT tests to compare these models in simulating these ranges. Generally, the time-hardening approach, for which the quality of fit is dependent on the chosen model, was found to work successfully. In this study, the selected models performed quite well, with the modified model showing the closest agreement to the test data. Thus, this approach has the potential to be applied for better modeling and prediction of pavement performance.

  • 33.
    Farah, Haneen
    KTH, School of Architecture and the Built Environment (ABE), Transport Science, Traffic and Logistics.
    Age and Gender Differences in Overtaking Maneuvers on Two-Lane Rural Highways2011In: Transportation Research Record, ISSN 0361-1981, E-ISSN 2169-4052, no 2248, p. 30-36Article in journal (Refereed)
    Abstract [en]

    For decades researchers have been pointing out significant differences in the driving behavior between young and old and between male and female drivers. There are many studies concerning age and gender differences in risk perception, traffic accident involvement, traffic violations, alcohol consumption, and risky driving. However, little effort has been focused on studying the behavioral differences in overtaking maneuvers on two-lane highways. A considerable percentage of the fatal accidents on two-lane highways is directly related to overtaking maneuvers. Therefore, the main focus of this study is to understand better the overtaking behavior of different drivers classified by their age and gender. Data on the overtaking behavior of 100 drivers were collected with an interactive driving simulator. Several scenarios of two-lane rural highways with different geometric and traffic conditions were developed. The results show interesting and significant differences in the overtaking behavior of drivers depending on their age and gender. These differences are mainly in the frequency of overtaking maneuvers, overtaking time duration, following distances, critical overtaking gaps, and desired driving speeds. Geometric and traffic conditions were also found to have a significant impact on drivers' overtaking behavior. The findings of this study contribute to the understanding of the overtaking behavior of different groups of drivers and thus have implications for road safety intervention programs and the development of effective risk reduction strategies adapted and targeted for different age and gender groups.

  • 34.
    Franklin, Joel
    KTH, School of Architecture and the Built Environment (ABE), Transport Science, Transport and Location Analysis. KTH, School of Architecture and the Built Environment (ABE), Centres, Centre for Transport Studies, CTS.
    Role of Context in Equity Effects of Congestion Pricing2012In: Transportation Research Record, ISSN 0361-1981, E-ISSN 2169-4052, no 2297, p. 29-37Article in journal (Refereed)
    Abstract [en]

    The equity effects of congestion pricing have come into focus as a potential hindrance to its acceptability in implementation around the world. Both theoretical arguments and empirical evidence about how the burden of the toll should fall on demographic groups have been mixed, depending on a variety of contextual factors such as automobile access, work schedule, flexibility, and spatial distribution of activities. Yet the evidence so far for implemented congestion pricing systems has not examined explicitly the role of such contextual factors. With the congestion pricing trial in Stockholm, Sweden, as a case study, this paper uses structural equation modeling to estimate a model of the role of age, income, and gender as independent variables; contextual factors as endogenous variables; and the change in automobile trips after congestion pricing as dependent variables. The findings indicated that gender was a significant factor in terms of the total effects and that three of the four contextual variables-access to a car, possession of a longterm transit pass, and having a workplace on the same side of the cordon as home-played significant mediating roles in the indirect effects of the demographic variables on trips by automobile. Moreover, it was found that gender was significant only when the contextual factors were included in the model. This finding suggested that a significant variable could be missed when such factors were omitted.

  • 35.
    Franklin, Joel P.
    et al.
    KTH, School of Architecture and the Built Environment (ABE), Transport and Economics, Transport and Location Analysis.
    Karlström, Anders
    KTH, School of Architecture and the Built Environment (ABE), Transport and Economics, Transport and Location Analysis.
    Travel Time Reliability for Stockholm Roadways Modeling Mean Lateness Factor2009In: Transportation Research Record, ISSN 0361-1981, E-ISSN 2169-4052, no 2134, p. 106-113Article in journal (Refereed)
    Abstract [en]

    In recent years, there has been an increasing awareness that travel time reliability, apart from expected travel time, is an important component of cost-benefit analysis, especially during congested traffic conditions. A common measure of travel time reliability is standard deviation, and it has been shown that this is a theoretically sound measure under scheduling constraints, provided that the mean lateness factor is known. Hence, in applied cost-benefit analyses, one will need both the standard deviation and the mean lateness factor. These analyses would be particularly simple if the mean lateness were constant across time of day and for different routes chosen. A study was done to explore how the mean lateness varies and how its variations can be approximated. With the use of travel time measurements on individual links, it is shown how mean lateness varies considerably across time and space. It is shown that mean lateness exhibits a time-varying pattern depending on the characteristics of congestion on the link. It is also shown that the location of the link in the network is a significant determinant. The resulting model for mean lateness represents a considerable improvement over existing practice, where the mean lateness is implicitly assumed constant, yet a large portion of its variation remains unexplained. The model is useful for informing future research but is of less value for predicting the mean lateness in broad applied settings.

  • 36. Gao, Song
    et al.
    Frejinger, Emma
    Ben-Akiva, Moshe
    Adaptive Route Choice Models in Stochastic Time-Dependent Networks2008In: Transportation Research Record, ISSN 0361-1981, E-ISSN 2169-4052, Vol. 2085, p. 136-143Article in journal (Refereed)
    Abstract [en]

    Adaptive route choice models are studied that explicitly capture travelers' route choice adjustments according to information on realized network conditions in stochastic time-dependent networks. Two types of adaptive route choice models are explored: an adaptive path model in which a sequence of path choice models are applied at intermediate decision nodes and a routing policy choice model in which the alternatives correspond to routing policies rather than paths at the origin. A routing policy in this study is a decision rule that maps from all possible pairs (e.g., node, time) to the next links out of the node. Existing route choice models that can be estimated on disaggregate revealed preferences assume a deterministic network setting from the traveler's perspective and cannot capture the traveler's proactive adaptive behavior under uncertain traffic conditions. The literature includes a number of algorithmic studies of optimal routing policy problems, but the estimation of a routing policy choice model is a new research area. The specifications of estimating the two adaptive route choice models are established and the feasibility of estimation from path observations is demonstrated on an illustrative network. Prediction results from three models-nonadaptive path model, adaptive path model, and routing policy model-are compared. The routing policy model is shown to better capture the option value of diversion than the adaptive path model. The difference between the two adaptive models and the nonadaptive model is larger in terms of expected travel time if the network is more stochastic, indicating that the benefit of adaptivity is more significant in a more unpredictable network.

  • 37. Gordon, Jason B.
    et al.
    Koutsopoulos, Harilaos N.
    KTH, School of Architecture and the Built Environment (ABE), Transport Science, Traffic and Logistics.
    Wilson, Nigel H. M.
    Attanucci, John P.
    Automated Inference of Linked Transit Journeys in London Using Fare-Transaction and Vehicle Location Data2013In: Transportation Research Record, ISSN 0361-1981, E-ISSN 2169-4052, no 2343, p. 17-24Article in journal (Refereed)
    Abstract [en]

    Urban public transit providers historically have planned and managed their networks and services with little knowledge of their customers' travel patterns. Although ticket gates and bus fareboxes yield counts of passenger activity in specific stations or vehicles, the relationships between these transactions-the origins, transfers, and destinations of individual passengers-typically have been acquired only through small, costly, and infrequent rider surveys. New methods for inferring the journeys of all riders on a large public transit network have been built on recent work into the use of automated fare collection and vehicle location systems for analysis of passenger behavior. Complete daily sets of data from London's Oyster farecard and the iBus vehicle location system were used to infer boarding and alighting times and locations for individual bus passengers and to infer transfers between passenger trips of various public modes, and origin-destination matrices of linked intermodal transit journeys that include the estimated flows of passengers not using farecards were constructed. The outputs were validated against surveys and traditional origin-destination matrices. The software implementation demonstrated that the procedure is efficient enough to be performed daily, allowing transit providers to observe travel behavior on all services at all times.

  • 38.
    Hesami, Ebrahim
    et al.
    KTH, School of Architecture and the Built Environment (ABE), Transport Science, Highway and Railway Engineering.
    Bidewell, Nathan
    Griffith School of Engineering .
    Birgisson, Björn
    KTH, School of Architecture and the Built Environment (ABE), Transport Science, Highway and Railway Engineering.
    Kringos, Niki
    KTH, School of Architecture and the Built Environment (ABE), Transport Science, Highway and Railway Engineering.
    Evaluation of Environmental Susceptibility of Bituminous Mastic Viscosity as a Function of Mineral and Biomass Fillers: 2013In: Transportation Research Record, ISSN 0361-1981, E-ISSN 2169-4052, no 2371, p. 23-31Article in journal (Refereed)
    Abstract [en]

    Bituminous mastics influence many other important asphalt mixture properties in addition to their own allowance for the load transfer in the aggregate skeleton. The influence of bituminous mastics extents to the overall stability of a mixture, air void distribution, bitumen draindown during transport, a mixture's workability during the laying process, and the overall in-time performance of the pavement. To understand the properties of asphalt mixtures and their resistance to environmentally induced failure mechanisms, it is paramount to study not only bitumen and the asphalt mixture but also the mastic itself. Current asphalt design procedures do not take mastic behavior into account, however; this omission leads to a significant flaw in the ability to design and predict asphalt concrete response. This paper presents the results of an ongoing research project to enhance the understanding of the mastic phase as well as to develop a new test protocol to characterize mastics. A description is given of the measurements of mastic viscosity for different types of mastics in which the bitumen source is kept as a constant but with varying fillers as well as concentrations. Environmental susceptibility was investigated by subjecting the samples to aging and moisture conditioning. Biomass fillers were included in some of the mastics, in addition to some of the traditional fillers, to show their impact on the viscosity under varying conditions. Results showed that the developed test protocol was able to identify clearly the impact of filler properties on the mastic viscosity. A critical filler concentration was identified beyond which the viscosity behavior became nonlinear. The results also showed that moisture and aging had significant effects on the viscosity of mastics.

  • 39.
    Hlotova, Yevheniia
    et al.
    KTH, School of Architecture and the Built Environment (ABE), Transport Science, Traffic and Logistics.
    Cats, Oded
    KTH, School of Architecture and the Built Environment (ABE), Transport Science, Traffic and Logistics. Delft Univ Technol, Dept Transport & Planning, Netherlands.
    Meijer, Sebastiaan
    KTH, School of Architecture and the Built Environment (ABE), Transport Science, Traffic and Logistics. Delft Univ Technol, Fac Technol Policy & Management, Netherlands.
    Measuring Bus Drivers' Occupational Stress Under Changing Working Conditions2014In: Transportation Research Record, ISSN 0361-1981, E-ISSN 2169-4052, no 2415, p. 13-20Article in journal (Refereed)
    Abstract [en]

    Stress is an immense problem in modern society; approximately half of all occupational illnesses are directly or indirectly related to stress. The work of a bus driver is typically associated with high stress levels that negatively influence individual well-being as well as workforce management. The current study examined the impact of newly proposed working conditions on bus drivers' occupational stress by monitoring heart rate and by collecting data on mental workload with a questionnaire in operational driving conditions. The main determinants of stress levels were identified through multiple regression analysis. Results indicated that bus drivers experienced considerably lower stress levels under a new control strategy that shifts the performance objective from schedule adherence to service regularity. Higher stress levels were recorded during extreme weather conditions and peak hours and among inexperienced drivers. The measurements were performed with low-cost sports devices that can easily be used by practitioners.

  • 40. Hossain, Maruf
    et al.
    Susilo, Yusak
    The exploration of rickshaw usage pattern and its social impacts in Dhaka city, Bangladesh2011In: Transportation Research Record, ISSN 0361-1981, E-ISSN 2169-4052, Vol. 2239, p. 74-83Article in journal (Refereed)
    Abstract [en]

    With primary data collected from rickshaw users in Dhaka, Bangladesh, this paper explores patterns of rickshaw use and the possible social impacts that may occur if rickshaws were banned from Dhaka. A survey of 450 rickshaw users from six different locations in Dhaka was carried out, and descriptive and multivariate (binomial and multinomial logit models) analyses were applied to explore the social impacts of rickshaws on various groups of society. The results show that the rickshaw plays a crucial role in Dhaka's transport system. The majority of people use the rickshaw as their main mode of transport for their commute and social and recreational trips. Use of the rickshaw as a school travel mode and its resilience during the monsoon period make the rickshaw invaluable for Dhaka transport and economic activity. The analyses further show that the level of importance of rickshaws is unique for each socioeconomic group. For instance, females and people from low- and middle-income groups are more likely to be socially excluded if the rickshaw were not available anymore. A multinomial logit examined a rickshaw-free scenario: results suggest that most of the modal shift would move toward auto-rickshaws and taxicabs, rather than other public transport modes, such as the bus.

  • 41.
    Kazagli, Evanthia
    et al.
    KTH, School of Architecture and the Built Environment (ABE), Transport Science.
    Koutsopoulos, Haris N.
    KTH, School of Architecture and the Built Environment (ABE), Transport Science, Traffic and Logistics.
    Estimation of Arterial Travel Time from Automatic Number Plate Recognition Data2013In: Transportation Research Record, ISSN 0361-1981, E-ISSN 2169-4052, no 2391, p. 22-31Article in journal (Refereed)
    Abstract [en]

    Automatic vehicle identification (AVI) systems are increasingly used for the collection of traffic data in urban and freeway networks. Several methods have been proposed for the estimation of travel times from AVI data, mainly for freeways. The problem of estimation of travel times in urban networks was examined. The main difference between freeway and urban networks is that urban network AVI data are often extremely noisy. A major part of that noise is attributed to vehicles that do not traverse the monitored section directly but stop for various reasons. A mixture model was proposed to capture the underlying states of the measurements of AVI travel times in urban areas. The hypothesis was that travel times are drawn from two (or more) populations, one representing normal movement through the network and one representing vehicles that stop for whatever reason. The method was applied with AVI data (collected through a system for automatic recognition of number plates) from a number of corridors in central Stockholm, Sweden. The model was estimated as a mixture-of two lognormal distributions, and bootstrap standard errors were calculated. The results illustrate the robustness of the method and its ability to identify the underlying distribution of the latent populations consistent with the characteristics of each route, while standard methods for outlier removal fail.

  • 42. Kim, H
    et al.
    Sokolov, K
    Poulikakos, L
    Partl, Manfred
    KTH, School of Architecture and the Built Environment (ABE), Transport Science, Highway and Railway Engineering.
    Fatigue Evaluation of Carbon FRP-Reinforced Porous Asphalt Composite System Using a Model Mobile Load Simulator2009In: Transportation Research Record, ISSN 0361-1981, E-ISSN 2169-4052, Vol. 2116, p. 108-117Article in journal (Refereed)
  • 43.
    Koutoulas, Anastasios
    et al.
    KTH, School of Architecture and the Built Environment (ABE), Transport Science, System Analysis and Economics.
    Franklin, Joel
    KTH, School of Architecture and the Built Environment (ABE), Transport Science, System Analysis and Economics.
    Eliasson, Jonas
    KTH, School of Architecture and the Built Environment (ABE), Transport Science.
    Assessing Nighttime Deliveries in Stockholm, Sweden2017In: Transportation Research Record, ISSN 0361-1981, E-ISSN 2169-4052, Vol. 2605, p. 54-60Article in journal (Refereed)
    Abstract [en]

    Off-peak-hour delivery programs are a promising but challenging concept for promoting sustainable urban logistics. Stockholm, Sweden, initialized a nighttime freight deliveries program in 2014, aimed at a more efficient and environmentally friendly delivery system within the central area of the city. The policy of shifting freight deliveries from daytime to off-peak hours generates a wide range of effects that can be analyzed from several angles. This paper identifies the social costs and benefits, how these are distributed between stakeholders, and their effects on the everyday life and operations of all interested parties. Accord-ing to information and data collected through in-depth interviews with private and public stakeholders, the social benefits mainly consist of increased efficiency and productivity for carriers and receivers, reduced transport costs, fuel cost savings, and reduced congestion and accidents when trucks are moved from peak to off-peak hours. Social costs may include increased noise levels and noise disturbances; additional staff requirements, equipment, and wage costs; and higher risks in handling goods deliveries at nighttime, especially in the case of unassisted deliv-eries. This paper concludes by discussing the lessons learned from the trial, challenges and opportunities that arose during implementation, and the implications for enhancement of off-peak-hour delivery in Stockholm and other cities.

  • 44.
    Koutsopoulos, Haris N.
    et al.
    KTH, School of Architecture and the Built Environment (ABE), Transport and Economics (closed 20110301).
    Wang, Zhigao
    Simulation of Urban Rail Operations: Application Framework2007In: Transportation Research Record, ISSN 0361-1981, E-ISSN 2169-4052, no 2006, p. 84-91Article in journal (Refereed)
    Abstract [en]

    Simulation models of urban rail operations are valuable tools for analysis of the operations of complex rail transit systems. A framework is presented for the application of rail simulation that includes calibration, validation, evaluation methodology, and interpretation of results. Methods that can be used at each step to facilitate the application are discussed. In particular, approaches are presented for calibration of model parameters and inputs, such as dynamic arrival and alighting rates at stations. Application of simulation tools can be greatly enhanced by the use of train circuit occupancy data collected by automated control systems. A new rail simulation model, SimMetro, specifically designed for service performance analysis taking into account the major sources of uncertainty in operations, is also presented. A case study is used to illustrate the applicability of the proposed framework in testing alternative real-time control strategies.

  • 45.
    Kringos, Nicole
    et al.
    Group of Mechanics of Structural Systems, Faculty of Civil Engineering and Geosciences, Delft University of Technology.
    Azari, H
    Micro-Scale Finite Element Analysis of Moisture Infiltration in the Modified Lottman test2009In: Transportation Research Record, ISSN 0361-1981, E-ISSN 2169-4052, Vol. 2, no 2127Article in journal (Refereed)
  • 46.
    Ma, Xiaoliang
    et al.
    KTH, School of Architecture and the Built Environment (ABE), Centres, Centre for Traffic Research, CTR.
    Andreasson, Ingmar
    KTH, School of Architecture and the Built Environment (ABE), Centres, Centre for Traffic Research, CTR.
    Statistical analysis of driver behavioral data in different regimes of the car-following stage2007In: Transportation Research Record, ISSN 0361-1981, E-ISSN 2169-4052, no 2018, p. 87-96Article in journal (Refereed)
    Abstract [en]

    An instrumented vehicle has been used to study car-following behavior on Swedish motorways. In this study, the previous data collection and pre-processing work were briefly reviewed. To understand the driving behavior in the car-following stage more clearly, the collected time series were classified into a number of regimes using unsupervised fuzzy clustering methods. Then, the statistical relations between the driver acceleration response and the perceptual variables in each regime were analyzed using correlation and regression methods. It was found that regime classification helps discern the behavioral variance between those regime clusters. According to the data analysis, some of the car-following regimes, for example, opening and braking, can be described adequately in the statistical sense by a linear regression model (Helly's model). Therefore, a multiple regime car-following model with simple model forms, for example, linear models, has the potential to robustly represent the general car-following behavior in most regimes.

  • 47.
    Ma, Xiaoliang
    et al.
    KTH, School of Architecture and the Built Environment (ABE), Centres, Centre for Traffic Research, CTR.
    Andréasson, Ingmar
    KTH, School of Architecture and the Built Environment (ABE), Centres, Centre for Traffic Research, CTR.
    Driver reaction delay estimation from real data and its application in GM-type model evaluation2006In: Transportation Research Record, ISSN 0361-1981, E-ISSN 2169-4052, no 1965, p. 130-141Article in journal (Refereed)
    Abstract [en]

    Driver behavior plays an important role in modeling vehicle dynamics in a traffic simulation environment. To study one element of the general driver behavior, that of car following, an advanced instrumented vehicle has been applied in dynamic data collection in real traffic flow on Swedishroads. This paper briefly introduces our car following data collection and smoothing methods. Moreover, we introduce spectrum analysis methods based on Fourier analysis of car following data to estimate driver reaction times, a crucial parameter of driver behavior. As an example, we calibrate a generalized GM-type model, an extension of the classical nonlinear GM model, in stable following regime based on the estimated driver reaction times. The calibrated model is then evaluated by closed-loop simulations.

  • 48. Novak, M.
    et al.
    Birgisson, Björn
    Dept. of Civ. and Coast. Engineering, University of Florida.
    Roque, R.
    Choubane, B.
    One-way and two-way directional heavy-vehicle simulator loading effects on rutting in hot-mix asphalt pavements2004In: Transportation Research Record, ISSN 0361-1981, E-ISSN 2169-4052, no 1896, p. 208-214Article in journal (Refereed)
    Abstract [en]

    Instability rutting generally occurs within the top 5 cm (2 in.) of the asphalt layer when the structural properties of the asphalt concrete are inadequate to resist the stresses imposed on it. It is generally believed that near-surface transverse shear stresses perpetuate instability rutting. Field observations of heavy-vehicle simulator testing noted greater rutting in one-way directional loading than with two-way directional loading, even at lower temperatures and with longer rest periods between load applications. An analysis of stress states in the asphalt pavement layer using the three-dimensional finite element commercial code ADINA showed that longitudinal stress path patterns varied between the different directional loadings. A hypothesis was developed that the differences in longitudinal plane stress path patterns between one-way and two-way directional loading could be attributed to the different levels of rutting. A viscoelastic model with load applications simulating the different directional loadings was constructed and used to test this hypothesis. The viscoelastic model results indicated qualitatively that even with greater relaxation times, one-way directional loading produces greater strains.

  • 49.
    Safi, Mohammed
    et al.
    KTH, School of Architecture and the Built Environment (ABE), Civil and Architectural Engineering, Structural Engineering and Bridges.
    Sundquist, Håkan
    KTH, School of Architecture and the Built Environment (ABE), Civil and Architectural Engineering, Structural Engineering and Bridges.
    Karoumi, Raid
    KTH, School of Architecture and the Built Environment (ABE), Civil and Architectural Engineering, Structural Engineering and Bridges.
    Racutanu, G.
    Integration of life-cycle cost analysis with bridge management systems: case study of the Swedish bridge and tunnel management system.2012In: Transportation Research Record, ISSN 0361-1981, E-ISSN 2169-4052, no 2292, p. 125-133Article in journal (Refereed)
    Abstract [en]

    Many countries use bridge management systems (BMSs), and many of these systems involve some form of life-cycle cost (LCC) analysis. Use of LCC analysis in bridge engineering is rare, however; the technique has been applied primarily in the operation phase to support decisions about bridges that already exist. Yet LCC analysis can be applied across the life of a bridge. This paper introduces the Swedish Bridge and Tunnel Management System (BaTMan). A comprehensive, integrated LCC implementation scheme takes into account the bridge investment and management processes in Sweden. The basic economic analytical tools as well as other helpful LCC analysis techniques are described. A case study demonstrates improvements in BaTMan as a factor in the decision whether to repair or to replace a bridge. Cost records for 1,987 bridges were used as input data in the case study. On the basis of the same records, the average real and anticipated initial costs of various bridge types in Sweden are presented schematically.

  • 50.
    Salour, Farhad
    et al.
    KTH, School of Architecture and the Built Environment (ABE), Transport Science, Highway and Railway Engineering.
    Erlingsson, Sigurdur
    Moisture-Sensitive and Stress-Dependent Behavior of Unbound Pavement Materials from In Situ Falling Weight Deflectometer Tests2013In: Transportation Research Record, ISSN 0361-1981, E-ISSN 2169-4052, no 2335, p. 121-129Article in journal (Refereed)
    Abstract [en]

    In an instrumented flexible pavement with a subsurface drainage system, a field study was performed to investigate the influence of water on the response of the pavement structure. The drainage system of the structure was clogged for 3 months; this condition allowed the ground-water to rise and the structure to undergo high moisture conditions. Reopening of the drainage system permitted the structure to approach its previous draining hydrological state. Along with monitoring of subsurface groundwater level and moisture content, the structural response of the pavement was studied by conducting frequent falling weight deflectometer tests with multilevel loads. The stress sensitivity of the unbound layers and the influence of moisture on their stiffness were studied, with the intent of using the data to determine the unbound materials' nonlinear parameters through a backcalculation algorithm. The groundwater level rose rapidly after the drainage system was clogged. This rise in groundwater level significantly affected the overall stiffness of the pavement structure, and the backcalculated stiffness of the unbound layers decreased as their moisture content increased. Furthermore, the unbound layers exhibited stress-dependent behavior to multilevel loads. The subgrade showed a stress-softening response in an unsaturated condition and stress-independent behavior in a saturated state. The granular layer exhibited stress-hardening behavior. Backcalculation of the unbound nonlinear parameters determined by the universal extended k-theta model revealed that the k(1) parameter decreased with increasing moisture content for both the unbound granular layer and the unsaturated fine-grained subgrade material.

12 1 - 50 of 63
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