| 1. |
- Abenoza, Roberto, et al.
(författare)
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Individual, Travel, and Bus Stop Characteristics Influencing Travelers’ Safety Perceptions
- 2018
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Ingår i: TRR Journal of transportation research board. - : Sage Publications. - 0361-1981.
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Tidskriftsartikel (refereegranskat)abstract
- Ensuring safety during door-to-door public transport trips is a fundamental challenge to service providers as safety influences individuals’ mobility. Using reported safety perceptions of travelers waiting at six bus stops with different characteristics in Stockholm, this study investigates factors that have an impact on determining travelers’ perceived safety and crime perceptions. This is done by assessing the importance of real-time information provision and the environmental characteristics of bus stops during the day and at night for different types of crime, after controlling for travelers’ individual and trip characteristics, and their previous experiences of victimization. Interaction effects of age, gender, and travel frequency are also tested. The results suggest that bus shelter characteristics, natural surveillance, and trustworthy real-time information are the most important factors influencing safety and crime perceptions. Additionally, safety perceptions are strongly influenced by previous experiences of victimization. The effect of perceived feelings about crime and safety are found to be nuanced by age and gender. Unlike some common beliefs, travelers: (1) feel less worried about becoming a victim of crime at bus stops associated with high crime rates; (2) prefer opaque shelters at night; and (3) have higher safety perceptions when the stop is located in an area of mixed land use. The impact of a bus stop’s number of passers-by is found to be insignificant. No direct or indirect effects can be attributed to frequency of travel by bus, indicating that familiar places and routine behavior have noeffect on declared crime and safety perceptions.
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| 2. |
- Allström, Andreas, 1978-, et al.
(författare)
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Hybrid Approach for Short-Term Traffic State and Travel Time Prediction on Highways
- 2016
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Ingår i: Transportation Research Record. - Washington, DC, USA : The National Academies of Sciences, Engineering, and Medicine. - 0361-1981 .- 2169-4052. ; 2554, s. 60-68
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Tidskriftsartikel (refereegranskat)abstract
- Traffic management and traffic information are essential in urban areas and require reliable knowledge about the current and future traffic state. Parametric and nonparametric traffic state prediction techniques have previously been developed with different advantages and shortcomings. While nonparametric prediction has shown good results for predicting the traffic state during recurrent traffic conditions, parametric traffic state prediction can be used during nonrecurring traffic conditions, such as incidents and events. Hybrid approaches have previously been proposed; these approaches combine the two prediction paradigms by using nonparametric methods for predicting boundary conditions used in a parametric method. In this paper, parametric and nonparametric traffic state prediction techniques are instead combined through assimilation in an ensemble Kalman filter. For nonparametric prediction, a neural network method is adopted; the parametric prediction is carried out with a cell transmission model with velocity as state. The results show that the hybrid approach can improve travel time prediction of journeys planned to commence 15 to 30 min into the future, with a prediction horizon of up to 50 min ahead in time to allow the journey to be completed
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| 3. |
- Ames, Alicia, et al.
(författare)
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Transport Workers' Perspective on Indigenous Transport and Climate Change Adaptation
- 2014
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Ingår i: Transportation Research Record. - : SAGE Publications. - 0361-1981 .- 2169-4052. ; :2451, s. 1-9
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Tidskriftsartikel (refereegranskat)abstract
- 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.
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| 4. |
- Andreasson, Ingmar J.
(författare)
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Personal Rapid Transit as Feeder-Distributor to Rail
- 2012
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Ingår i: Transportation Research Record. - : SAGE Publications. - 0361-1981 .- 2169-4052. ; :2275, s. 88-93
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Tidskriftsartikel (refereegranskat)abstract
- 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%.
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| 5. |
- Antoniou, Constantinos, et al.
(författare)
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Estimation of Traffic Dynamics Models with Machine Learning Methods
- 2006
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Ingår i: Transportation Research Record. - 0361-1981 .- 2169-4052. ; 1965, s. 103-111
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Tidskriftsartikel (refereegranskat)abstract
- 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.
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| 6. |
- Antoniou, C, et al.
(författare)
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Incorporating Automated Vehicle Identification Data into Origin-Destination Estimation
- 2004
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Ingår i: TRANSPORTATION NETWORK MODELING 2004. - Istanbul, Turkey : SAGE Publications. ; , s. 37-44
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Konferensbidrag (refereegranskat)abstract
- A methodology for the incorporation of automated vehicle identification (AVI) data into origin-destination (O-D) estimation and prediction is presented. AVI technologies facilitate the collection of useful data, such as point-to-point travel times and subpath flows. A framework for the incorporation of AVI data into the well-established O-D estimation and prediction process is presented. Improvements are proposed for both the formulation and the inputs to the O-D estimation and prediction model. Furthermore, as the O-D estimation and prediction process is often used in the traffic estimation and prediction context, approaches to the incorporation of AVI data into other areas of the dynamic traffic assignment framework are outlined. Performance and computational issues are also considered, and the results of a case study are presented to demonstrate the approach.
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| 7. |
- Antoniou, Constantinos, et al.
(författare)
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On-line Calibration of Traffic Prediction Models
- 2005
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Ingår i: Transportation Research Record. - 0361-1981 .- 2169-4052. ; 1934, s. 235-245
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Tidskriftsartikel (refereegranskat)abstract
- 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.
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| 8. |
- Balakrishna, Ramachandran, et al.
(författare)
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A Simulation-based Evaluation of Advanced Traveler Information Systems
- 2005
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Ingår i: Transportation Research Record. - : Transportation Research Board of the National Academies. - 0361-1981 .- 2169-4052. ; 1910, s. 90-98
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Tidskriftsartikel (refereegranskat)abstract
- 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.
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| 9. |
- Balakrishna, R., et al.
(författare)
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Calibration of Microscopic Traffic Simulation Models : Methods and Application
- 2007
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Ingår i: Transportation Research Record. - : SAGE Publications. - 0361-1981 .- 2169-4052. ; :1999, s. 198-207
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Tidskriftsartikel (refereegranskat)abstract
- 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.
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| 10. |
- Balakrishna, Ramachandran, et al.
(författare)
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Incorporating Within-Day Transitions in Simultaneous Offline Estimation of Dynamic Origin-Destination Flows Without Assignment Matrices
- 2008
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Ingår i: Transportation Research Record. - : SAGE Publications. - 0361-1981 .- 2169-4052. ; :2085, s. 31-38
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Tidskriftsartikel (refereegranskat)abstract
- 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.
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