| 1. |
- Abrahamsson, Lars, et al.
(author)
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An electromechanical moving load fixed node position and fixed node number railway power supply systems optimization model
- 2013
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In: Transportation Research Part C. - : Elsevier BV. - 0968-090X .- 1879-2359. ; 30, s. 23-40
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Journal article (peer-reviewed)abstract
- This paper presents an optimization model for simulations of railway power supply systems. It includes detailed power systems modeling, train movements in discretized time considering running resistance and other mechanical constraints, and the voltage-drop-induced reduction of possible train tractive forces. The model has a fixed number of stationary power system nodes, which alleviates optimized operation overtime. The proposed model uses SOS2 (Special Ordered Sets of type 2) variables to distribute the train loads to the two most adjacent power system nodes available. The impacts of the number of power system nodes along the contact line and the discretized time step length on model accuracy and computation times are investigated. The program is implemented in GAMS. Experiences from various solver choices are also discussed. The train traveling times are minimized in the example. Other studies could e.g. consider energy consumption minimization. The numerical example is representative for a Swedish decentralized, rotary-converter fed railway power supply system. The proposed concept is however generalizable and could be applied for all kinds of moving load power system studies.
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| 2. |
- Ahlström, Christer, et al.
(author)
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Fit-for-duty test for estimation of drivers sleepiness level: Eye movements improve the sleep/wake predictor
- 2013
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In: Transportation Research Part C. - : Elsevier. - 0968-090X .- 1879-2359. ; 26, s. 20-32
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Journal article (peer-reviewed)abstract
- Driver sleepiness contributes to a considerable proportion of road accidents, and a fit-for-duty test able to measure a drivers sleepiness level might improve traffic safety. The aim of this study was to develop a fit-for-duty test based on eye movement measurements and on the sleep/wake predictor model (SWP, which predicts the sleepiness level) and evaluate the ability to predict severe sleepiness during real road driving. Twenty-four drivers participated in an experimental study which took place partly in the laboratory, where the fit-for-duty data were acquired, and partly on the road, where the drivers sleepiness was assessed. A series of four measurements were conducted over a 24-h period during different stages of sleepiness. Two separate analyses were performed; a variance analysis and a feature selection followed by classification analysis. In the first analysis it was found that the SWP and several eye movement features involving anti-saccades, pro-saccades, smooth pursuit, pupillometry and fixation stability varied significantly with different stages of sleep deprivation. In the second analysis, a feature set was determined based on floating forward selection. The correlation coefficient between a linear combination of the acquired features and subjective sleepiness (Karolinska sleepiness scale, KSS) was found to be R = 0.73 and the correct classification rate of drivers who reached high levels of sleepiness (KSS andgt;= 8) in the subsequent driving session was 82.4% (sensitivity = 80.0%, specificity = 84.2% and AUC = 0.86). Future improvements of a fit-for-duty test should focus on how to account for individual differences and situational/contextual factors in the test, and whether it is possible to maintain high sensitive/specificity with a shorter test that can be used in a real-life environment, e.g. on professional drivers.
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| 3. |
- Antoniou, C., et al.
(author)
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Dynamic data-driven local traffic state estimation and prediction
- 2013
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In: Transportation Research Part C. - : Elsevier BV. - 0968-090X .- 1879-2359. ; 34, s. 89-107
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Journal article (peer-reviewed)abstract
- Traffic state prediction is a key problem with considerable implications in modern traffic management. Traffic flow theory has provided significant resources, including models based on traffic flow fundamentals that reflect the underlying phenomena, as well as promote their understanding. They also provide the basis for many traffic simulation models. Speed-density relationships, for example, are routinely used in mesoscopic models. In this paper, an approach for local traffic state estimation and prediction is presented, which exploits available (traffic and other) information and uses data-driven computational approaches. An advantage of the method is its flexibility in incorporating additional explanatory variables. It is also believed that the method is more appropriate for use in the context of mesoscopic traffic simulation models, in place of the traditional speed-density relationships. While these general methods and tools are pre-existing, their application into the specific problem and their integration into the proposed framework for the prediction of traffic state is new. The methodology is illustrated using two freeway data sets from Irvine, CA, and Tel Aviv, Israel. As the proposed models are shown to outperform current state-of-the-art models, they could be valuable when integrated into existing traffic estimation and prediction models.
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| 4. |
- Farah, Haneen, et al.
(author)
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Do cooperative systems make drivers' car-following behavior safer?
- 2014
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In: Transportation Research Part C. - : Elsevier BV. - 0968-090X .- 1879-2359. ; 41, s. 61-72
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Journal article (peer-reviewed)abstract
- The main goal of in-vehicle technologies and co-operative services is to reduce congestion and increase traffic safety. This is achieved by alerting drivers on risky traffic conditions ahead of them and by exchanging traffic and safety related information for the particular road segment with nearby vehicles. Road capacity, level of service, safety, and air pollution are impacted to a large extent by car-following behavior of drivers. Car-following behavior is an essential component of micro-simulation models. This paper investigates the impact of an infrastructure-to-vehicle (I2V) co-operative system on drivers' car-following behavior. Test drivers in this experiment drove an instrumented vehicle with and without the system. Collected trajectory data of the subject vehicle and the vehicle in front, as well as socio-demographic characteristics of the test drivers were used to estimate car-following models capturing their driving behavior with and without the I2V system. The results show that the co-operative system harmonized the behavior of drivers and reduced the range of acceleration and deceleration differences among them. The observed impact of the system was largest on the older group of drivers.
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| 5. |
- Farah, Haneen, et al.
(author)
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Evaluation of the effect of cooperative infrastructure-to-vehicle systems on driver behavior
- 2012
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In: Transportation Research Part C. - : Elsevier BV. - 0968-090X .- 1879-2359. ; 21:1, s. 42-56
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Journal article (peer-reviewed)abstract
- In-vehicle technologies and co-operative services have potential to ease congestion problems and improve traffic safety. This paper investigates the impact of infrastructure-to-vehicle co-operative systems, case of CO-OPerative SystEms for Intelligent Road Safety (COOPERS), on driver behavior. Thirty-five test drivers drove an instrumented vehicle, twice, with and without the system. Data related to driving behavior, physiological measurements, and user acceptance was collected. A macro-level approach was used to evaluate the potential impact of such systems on driver behavior and traffic safety. The results in terms of speeds, following gaps, and physiological measurements indicate a positive impact. Furthermore, drivers' opinions show that the system is in general acceptable and useful.
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| 6. |
- Fosgerau, Mogens, et al.
(author)
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Valuing travel time variability : Characteristics of the travel time distribution on an urban road
- 2012
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In: Transportation Research Part C. - : Elsevier BV. - 0968-090X .- 1879-2359. ; 24, s. 83-101
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Journal article (peer-reviewed)abstract
- This paper provides a detailed empirical investigation of the distribution of travel times on an urban road for valuation of travel time variability. Our investigation is premised on the use of a theoretical model with a number of desirable properties. The definition of the value of travel time variability depends on certain properties of the distribution of random travel times that require empirical verification. Applying a range of nonparametric statistical techniques to data giving minute-by-minute travel times for a congested urban road over a period of five months, we show that the standardized travel time is roughly independent of the time of day as required by the theory. Except for the extreme right tail, a stable distribution seems to fit the data well. The travel time distributions on consecutive links seem to share a common stability parameter such that the travel time distribution for a sequence of links is also a stable distribution. The parameters of the travel time distribution for a sequence of links can then be derived analytically from the link level distributions.
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| 7. |
- Gao, Song, et al.
(author)
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Adaptive route choices in risky traffic networks : A prospect theory approach
- 2010
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In: Transportation Research Part C. - : Elsevier BV. - 0968-090X .- 1879-2359. ; 18:5, s. 727-740
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Journal article (peer-reviewed)abstract
- This paper deals with route choice models capturing travelers' strategic behavior when adapting to revealed traffic conditions en route in a stochastic network. The strategic adaptive behavior is conceptualized as a routing policy, defined as a decision rule that maps from all possible revealed traffic conditions to the choices of next link out of decision nodes, given information access assumptions. In this paper, we use a specialized example where a variable message sign provides information about congestion status on outgoing links. We view the problem as choice under risk and present a routing policy choice model based on the cumulative prospect theory (CPT), where utility functions are nonlinear in probabilities and thus flexible attitudes toward risk can be captured. In order to illustrate the differences between routing policy and non-adaptive path choice models as well as differences between models based on expected utility (EU) theory and CPT, we estimate models based on synthetic data and compare them in terms of prediction results. There are large differences in path share predictions and the results demonstrate the flexibility of the CPT model to represent varying degrees of risk aversion and risk seeking depending on the outcome probabilities.
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| 8. |
- Hamilton, Carl, et al.
(author)
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Costs and benefits of the European directive on road tolling interoperability
- 2013
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In: Transportation Research Part C. - : Elsevier BV. - 0968-090X .- 1879-2359. ; 30, s. 221-238
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Journal article (peer-reviewed)abstract
- Pricing of road use in the form of tolls, congestion charges, kilometre tax and other similar schemes, is becoming increasingly common. Each toll road operator has so far decided on its own how to design and implement systems for collecting road user charges, causing a plethora of system and scheme designs. As a measure to reduce the drawbacks of such differences, the European Union has passed legislation aiming at making available interoperable road charging services, valid across all charging systems a vehicle might pass during a European journey. This legislation is setting the bar high, requiring that virtually every charging system in the Union be covered. We analyse the costs and benefits caused by this regulation, and if an adjusted regulation can improve these results. We conclude that the new legislation yields a social loss ranging from 100 to just above 500 million Euros annually. Policy suggestions to improve this result are also provided.
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| 9. |
- Hamilton, Carl J., et al.
(author)
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Vertical separation as means to establish interoperability in road tolling in Europe
- 2011
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In: Transportation Research Part C. - : Elsevier BV. - 0968-090X .- 1879-2359. ; 19:6, s. 1019-1032
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Journal article (peer-reviewed)abstract
- As more European roads become tolled by various means, an increasing share of road users become subject to more than one tolling scheme in their regular driving. This can be especially burdensome for long distance hauliers, who may pass several countries and tolled motorway systems during the course of 1 day. For this reason, a range of projects have been initiated attempting to increase the level of interoperability between tolling systems, many of which with only limited success. By analyzing current incentives, costs and benefits for toll operators and road users, we conclude firstly that the current level of interoperability is likely to be lower than socially optimal, and secondly that a direct regulation making the provision of interoperability mandatory is likely to be in excess of what is socially optimal. We argue that vertically separating the monopolistic toll operators could be a cost-efficient way to achieve a socially optimal level of interoperability as a equilibrium market outcome.
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| 10. |
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