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  Subjects -> TRANSPORTATION (Total: 144 journals)
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TRANSPORTATION (90 journals)

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Journal Cover Transportation Research Part C: Emerging Technologies     [SJR: 1.605]   [H-I: 47]
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   Hybrid Journal Hybrid journal (It can contain Open Access articles)
   ISSN (Print) 0968-090X
   Published by Elsevier Homepage  [2585 journals]
  • Autonomous cars: The tension between occupant experience and intersection
           capacity
    • Abstract: Publication date: March 2015
      Source:Transportation Research Part C: Emerging Technologies, Volume 52
      Author(s): Scott Le Vine , Alireza Zolfaghari , John Polak
      Systems that enable high levels of vehicle-automation are now beginning to enter the commercial marketplace. Road vehicles capable of operating independently of real-time human control under an increasing set of circumstances will likely become more widely available in the near future. Such vehicles are expected to bring a variety of benefits. Two such anticipated advantages (relative to human-driver vehicle control) are said to be increased road network capacity and the freeing up of the driver-occupant’s time to engage in their choice of leisurely or economically-productive (non-driving) tasks. In this study we investigate the implications for intersection capacity and level-of-service of providing occupants of automated (without real-time human control), autonomously-operating (without vehicle-to-X communication) cars with ride quality that is equivalent (in terms of maximum rates of longitudinal and lateral acceleration) to two types of rail systems: [urban] light rail transit and [inter-urban] high-speed rail. The literature suggests that car passengers start experiencing discomfort at lower rates of acceleration than car drivers; it is therefore plausible that occupants of an autonomously-operating vehicle may wish to instruct their vehicle to maneuver in a way that provides them greater ride comfort than if the vehicle-control algorithm simply mimicked human-driving-operation. On the basis of traffic microsimulation analysis, we found that restricting the dynamics of autonomous cars to the acceleration/deceleration characteristics of both rail systems leads to reductions in a signalized intersection’s vehicle-processing capacity and increases in delay. The impacts were found to be larger when constraining the autonomous cars’ dynamics to the more-restrictive acceleration/deceleration profile of high-speed rail. The scenarios we analyzed must be viewed as boundary conditions, because autonomous cars’ dynamics were by definition never allowed to exceed the acceleration/deceleration constraints of the rail systems. Appropriate evidence regarding motorists’ preferences does not exist at present; establishing these preferences is an important item for the future research agenda. This paper concludes with a brief discussion of research needs to advance this line of inquiry.


      PubDate: 2015-01-25T09:29:46Z
       
  • Decentralized signal control for urban road networks
    • Abstract: Publication date: Available online 16 January 2015
      Source:Transportation Research Part C: Emerging Technologies
      Author(s): Tung Le , Péter Kovács , Neil Walton , Hai L. Vu , Lachlan L.H. Andrew , Serge S.P. Hoogendoorn
      We propose in this paper a decentralized traffic signal control policy for urban road networks. Our policy is an adaptation of a so-called BackPressure scheme which has been widely recognized in data network as an optimal throughput control policy. We have formally proved that our proposed BackPressure scheme, with fixed cycle time and cyclic phases, stabilizes the network for any feasible traffic demands. Simulation has been conducted to compare our BackPressure policy against other existing distributed control policies in various traffic and network scenarios. Numerical results suggest that the proposed policy can surpass other policies both in terms of network throughput and congestion.


      PubDate: 2015-01-21T14:56:56Z
       
  • Self-organizing traffic signals using secondary extension and dynamic
           coordination
    • Abstract: Publication date: November 2014
      Source:Transportation Research Part C: Emerging Technologies, Volume 48
      Author(s): Burak Cesme , Peter G. Furth
      Actuated traffic signal control logic has many advantages because of its responsiveness to traffic demands, short cycles, effective use of capacity leading to and recovering from oversaturation, and amenability to aggressive transit priority. Its main drawback has been its inability to provide good progression along arterials. However, the traditional way of providing progression along arterials, coordinated–actuated control with a common, fixed cycle length, has many drawbacks stemming from its long cycle lengths, inflexibility in recovering from priority interruptions, and ineffective use of capacity during periods of oversaturation. This research explores a new paradigm for traffic signal control, “self-organizing signals,” based on local actuated control but with some additional rules that create coordination mechanisms. The primary new rules proposed are for secondary extensions, in which the green may be held to serve an imminently arriving platoon, and dynamic coordination, in which small groups of closely spaced signals communicate with one another to cycle synchronously with the group’s critical intersection. Simulation tests in VISSIM performed on arterial corridors in Massachusetts and Arizona show overall delay reductions of up to 14% compared to an optimized coordinated–actuated scheme where there is no transit priority, and more than 30% in scenarios with temporary oversaturation. Tests also show that with self-organizing control, transit signal priority can be more effective than with coordinated–actuated control, reducing transit delay by about 60%, or 12 to 14s per intersection with little impact on traffic delay.


      PubDate: 2015-01-15T13:53:20Z
       
  • Editorial Board/Copyright Information
    • Abstract: Publication date: November 2014
      Source:Transportation Research Part C: Emerging Technologies, Volume 48




      PubDate: 2015-01-15T13:53:20Z
       
  • Application of advanced sampling for efficient probabilistic traffic
           modelling
    • Abstract: Publication date: December 2014
      Source:Transportation Research Part C: Emerging Technologies, Volume 49
      Author(s): Simeon C. Calvert , Henk Taale , Maaike Snelder , Serge P. Hoogendoorn
      In probabilistic traffic models, consideration of stochasticity in the dynamics of traffic gives a closer representation of a traffic system in comparison to that of a deterministic approach. Monte Carlo simulation is a broadly accepted method to consider variations in traffic within modelling. In this contribution, the possibility of increasing the efficiency of probabilistic traffic flow models using Monte Carlo simulation is analysed using variance reduction techniques and sequencing, for varied capacity and traffic demand values. The techniques of Importance Sampling, Latin Hypercube Sampling and Quasi-Random Sequencing are compared in a dynamic macroscopic traffic model to demonstrate the effectiveness of these techniques for reduction of the computational load when considering multiple input variations. Demonstration of their efficiency in traffic modelling is expected to lead to a wider application of the methods in practice.


      PubDate: 2015-01-15T13:53:20Z
       
  • Evacuation traffic dynamics
    • Abstract: Publication date: December 2014
      Source:Transportation Research Part C: Emerging Technologies, Volume 49
      Author(s): Vinayak Dixit , Brian Wolshon
      Historically, evacuation models have relied on values of road capacity that are estimated based on Highway Capacity Manual methods or those observed during routine non-emergency conditions. The critical assumption in these models is that capacity values and traffic dynamics do not differ between emergency and non-emergency conditions. This study utilized data collected during Hurricanes Ivan (2004), Katrina (2005) and Gustav (2008) to compare traffic characteristics during mass evacuations with those observed during routine non-emergency operations. From these comparisons it was found that there exists a consistent and fundamental difference between traffic dynamics under evacuation conditions and those under routine non-emergency periods. Based on the analysis, two quantities are introduced: “maximum evacuation flow rates” (MEFR) and “maximum sustainable evacuation flow rates” (MSEFR). Based on observation, the flow rates during evacuations were found to reach a maximum value of MEFR followed by a drop in flow rate to a MSEFR that was able to be sustained over several hours, or until demand dropped below that necessary to completely saturate the section. It is suggested that MEFR represents the true measure of the “capacity”. These findings are important to a number of key policy-shaping factors that are critical to evacuation planning. Most important among these is the strong suggestion of policy changes that would shift away from the use of traditional capacity estimation techniques and toward values based on direct observation of traffic under evacuation conditions.


      PubDate: 2015-01-15T13:53:20Z
       
  • Solving a discrete multimodal transportation network design problem
    • Abstract: Publication date: December 2014
      Source:Transportation Research Part C: Emerging Technologies, Volume 49
      Author(s): Lihui Zhang , Hai Yang , Di Wu , Dianhai Wang
      This paper investigates the multimodal network design problem (MMNDP) that optimizes the auto network expansion scheme and bus network design scheme in an integrated manner. The problem is formulated as a single-level mathematical program with complementarity constraints (MPCC). The decision variables, including the expanded capacity of auto links, the layout of bus routes, the fare levels and the route frequencies, are transformed into multiple sets of binary variables. The layout of transit routes is explicitly modeled using an alternative approach by introducing a set of complementarity constraints. The congestion interaction among different travel modes is captured by an asymmetric multimodal user equilibrium problem (MUE). An active-set algorithm is employed to deal with the MPCC, by sequentially solving a relaxed MMNDP and a scheme updating problem. Numerical tests on nine-node and Sioux Falls networks are performed to demonstrate the proposed model and algorithm.


      PubDate: 2015-01-15T13:53:20Z
       
  • Comparing INRIX speed data against concurrent loop detector stations over
           several months
    • Abstract: Publication date: December 2014
      Source:Transportation Research Part C: Emerging Technologies, Volume 49
      Author(s): Seoungbum Kim , Benjamin Coifman
      Many real-time traffic-monitoring applications only require speed or travel time. In recent years INRIX Traffic has started collecting and selling real-time speed data collected from “a variety of sources.” The clients include direct to consumer and operating agencies alike. So far the INRIX speed data have received little independent evaluation in the literature, with only a few published studies. The current study exploits a unique juncture as the Ohio Department of Transportation transitioned from loop detectors to third party traffic data for real time management. The two traffic surveillance systems operated concurrently for about half a year in Columbus, Ohio, USA. This paper uses two months of the concurrent data to evaluate INRIX performance on 14 mi of I-71, including both recurrent and non-recurrent events. The work compared reported speeds from INRIX against the concurrent loop detector data, as detailed herein. Three issues became apparent: First, the reported INRIX speeds tend to lag the loop detector measurements by almost 6min. This latency appears to be within INRIX specifications, but from an operational standpoint it is important that time sensitive applications account for it, e.g., traffic responsive ramp metering. Second, although INRIX reports speed every minute, most of the time the reported speed is identical to the previous sample, suggesting that INRIX is effectively calculating the speeds over a longer period than it uses to report the speeds. This work observed an effective average sampling period of 3–5min, with many periods of repeated reported speed lasting in excess of 10min. Third, although INRIX reports two measures of confidence, these confidence measures do not appear to reflect the latency or the occurrence of repeated INRIX reported speeds.


      PubDate: 2015-01-15T13:53:20Z
       
  • Methods for pre-processing smartcard data to improve data quality
    • Abstract: Publication date: December 2014
      Source:Transportation Research Part C: Emerging Technologies, Volume 49
      Author(s): Steve Robinson , Baskaran Narayanan , Nelson Toh , Francisco Pereira
      In recent years smartcards have been implemented in many transit systems around the world as a means by which passengers pay for travel. In addition to allowing speedier boardings there are many secondary benefits of smartcard systems including better understanding of travel patterns and behaviour of travellers. Such research is dependent on the smartcard correctly recording the boarding stop, and where available the alighting stop. It is also dependent on the smartcard system correctly aggregating individual rides into trips. This paper identifies causes for why smartcard systems may not correctly record such information. The first contribution of the paper is to propose a set of rules to aggregate individual rides into a single trip. This is critical in the research of activity based modelling as well as for correctly charging the passenger. The second contribution of the paper is to provide an approach to identify erroneous tap-out data, either caused by system problems or by the user. An approach to detecting this phenomenon is provided. The output from this analysis is then used to identify faulty vehicles or data supply using the “comparison against peers approach”. This third contribution of the paper identifies where transit agencies and operators should target resources to improve performance of their Automatic Vehicle Location systems. This method could also be used to identify users who appear to be tapping out too early. The approaches are tested using smartcard data from the Singapore public transport network from one week in April 2011. The results suggest that approximately 7.7% of all smartcard rides recorded the passenger as alighting one stop before the bus stop that they most probably alighted at. A further 0.7% of smartcard rides recorded the passenger as alighting more than one stop before the bus stop that they most probably alighted at. There was no evidence that smartcards overestimated the distance travelled by the passenger.


      PubDate: 2015-01-15T13:53:20Z
       
  • A GIS-based tool to support air traffic management during explosive
           volcanic eruptions
    • Abstract: Publication date: December 2014
      Source:Transportation Research Part C: Emerging Technologies, Volume 49
      Author(s): Chiara Scaini , Arnau Folch , Tatjana Bolić , Lorenzo Castelli
      We present a methodology to estimate the impacts of volcanic ash dispersal on civil aviation and a software tool aimed at assisting air traffic management in the event of ash-contaminated airspace. The tool merges atmospheric dispersal model forecasts with air traffic data in a map-based platform to produce tables and maps showing potentially affected airports, flights and airspace sectors. Impacts can be estimated based on user-defined ash concentration thresholds, or on the amount of ash potentially ingested by airplanes flying through diluted ash clouds. The impact can be assessed on single Flight Level (FL) slabs, or across the whole vertical airspace. The procedure is automated within a Geographical Information System (GIS). For illustrative purposes, we estimate the potential impacts on the European air traffic of an eruption from Katla volcano in Iceland, assuming a “worst-case” meteorological scenario. We compare the capabilities of the tool with those of similar existing software and justify our design choices. Finally, we discuss the use of the tool in current and future air traffic management strategies during explosive volcanic eruptions.


      PubDate: 2015-01-15T13:53:20Z
       
  • Editorial Board/Copyright Information
    • Abstract: Publication date: December 2014
      Source:Transportation Research Part C: Emerging Technologies, Volume 49




      PubDate: 2015-01-15T13:53:20Z
       
  • Signal control optimization for automated vehicles at isolated signalized
           intersections
    • Abstract: Publication date: December 2014
      Source:Transportation Research Part C: Emerging Technologies, Volume 49
      Author(s): Zhuofei Li , Lily Elefteriadou , Sanjay Ranka
      Traffic signals at intersections are an integral component of the existing transportation system and can significantly contribute to vehicular delay along urban streets. The current emphasis on the development of automated (i.e., driverless and with the ability to communicate with the infrastructure) vehicles brings at the forefront several questions related to the functionality and optimization of signal control in order to take advantage of automated vehicle capabilities. The objective of this research is to develop a signal control algorithm that allows for vehicle paths and signal control to be jointly optimized based on advanced communication technology between approaching vehicles and signal controller. The algorithm assumes that vehicle trajectories can be fully optimized, i.e., vehicles will follow the optimized paths specified by the signal controller. An optimization algorithm was developed assuming a simple intersection with two single-lane through approaches. A rolling horizon scheme was developed to implement the algorithm and to continually process newly arriving vehicles. The algorithm was coded in MATLAB and results were compared against traditional actuated signal control for a variety of demand scenarios. It was concluded that the proposed signal control optimization algorithm could reduce the ATTD by 16.2–36.9% and increase throughput by 2.7–20.2%, depending on the demand scenario.


      PubDate: 2015-01-15T13:53:20Z
       
  • Analysis of a cooperative variable speed limit system using microscopic
           traffic simulation
    • Abstract: Publication date: Available online 19 December 2014
      Source:Transportation Research Part C: Emerging Technologies
      Author(s): Ellen Grumert , Xiaoliang Ma , Andreas Tapani
      Variable speed limit systems where variable message signs are used to show speed limits adjusted to the prevailing road or traffic conditions are installed on motorways in many countries. The objectives of variable speed limit system installations are often to decrease the number of accidents and to increase traffic efficiency. Currently, there is an interest in exploring the potential of cooperative intelligent transport systems including communication between vehicles and/or vehicles and the infrastructure. In this paper, we study the potential benefits of introducing infrastructure to vehicle communication, autonomous vehicle control and individualized speed limits in variable speed limit systems. We do this by proposing a cooperative variable speed limit system as an extension of an existing variable speed limit system. In the proposed system, communication between the infrastructure and the vehicles is used to transmit variable speed limits to upstream vehicles before the variable message signs become visible to the drivers. The system is evaluated by the means of microscopic traffic simulation. Traffic efficiency and environmental effects are considered in the analysis. The results of the study show benefits of the infrastructure to vehicle communication, autonomous vehicle control and individualized speed limits for variable speed limit systems in the form of lower acceleration rates and thereby harmonized traffic flow and reduced exhaust emissions.


      PubDate: 2015-01-15T13:53:20Z
       
  • Real time traffic flow outlier detection using short-term traffic
           conditional variance prediction
    • Abstract: Publication date: January 2015
      Source:Transportation Research Part C: Emerging Technologies, Volume 50
      Author(s): Jianhua Guo , Wei Huang , Billy M. Williams
      Outliers in traffic flow series represent uncommon events occurring in the roadway systems and outlier detection and investigation will help to unravel the mechanism of such events. However, studies on outlier detection and investigations are fairly limited in transportation field where a vast volume of traffic condition data has been collected from traffic monitoring devices installed in many roadway systems. Based on an online algorithm that has the ability of jointly predict the level and the conditional variance of the traffic flow series, a real time outlier detection method is proposed and implemented. Using real world data collected from four regions in both the United States and the United Kingdom, it was found that outliers can be detected using the proposed detection strategy. In addition, through a comparative experimental study, it was shown that the information contained in the outliers should be assimilated into the forecasting system to enhance its ability of adapting to the changing patterns of the traffic flow series. Moreover, the investigation into the effects of outliers on the forecasting system structure showed a significant connection between the outliers and the forecasting system parameters changes. General conclusions are provided concerning the analyses with future work recommended to investigate the underlying outlier generating mechanism and outlier treatment strategy in transportation applications.


      PubDate: 2015-01-15T13:53:20Z
       
  • Applying telecommunications methodology to road safety for rear-end
           collision avoidance
    • Abstract: Publication date: January 2015
      Source:Transportation Research Part C: Emerging Technologies, Volume 50
      Author(s): Francesco Benedetto , Alessandro Calvi , Fabrizio D’Amico , Gaetano Giunta
      This work aims at applying telecommunications methodologies to road safety for preventing rear-end collisions. This contribution can be considered as a pilot study to verify and assess the reliability of a new model and procedure for collision warning system based on low-cost inter-vehicular communications (only a cheap radio transmitter/receiver mounted on each vehicle is needed), where Global Positioning Systems (GPS) and other distance vector-based networks are not employed. A signal processing method, namely the binomial test, aimed at detecting approaching sources in infrastructure-less vehicular communications is here proposed and discussed. The detection probability of the method is evaluated versus several driving conditions, in terms of relative speeds and distances between vehicles. In addition, the Time To Collision (TTC), generally required before declaring a correct detection by existing collision systems implemented in recent vehicles, is evaluated for several driving scenarios characterized by different setting parameters. Our numerical results confirm the validity of such an approach in preventing rear-end collisions, allowing a fast detection of approaching sources.


      PubDate: 2015-01-15T13:53:20Z
       
  • Integrity of estimates of the two-fluid model and gender impacts
    • Abstract: Publication date: January 2015
      Source:Transportation Research Part C: Emerging Technologies, Volume 50
      Author(s): Anurag Pande , James Loy , Vinayak V. Dixit , Katherine Spansel , Brian Wolshon
      This paper summarizes a research study to develop a methodology for utilizing naturalistic Global Positioning System (GPS) driving data for two-fluid model estimation. The two-fluid vehicular traffic flow model describes traffic flow on a street network as a mix of stopped and running vehicles. The parameters of the model essentially represent ‘free flow’ travel time and the level of interaction among vehicles. These parameters have traditionally been used to evaluate roadway networks and corridors with partially limited access. However, the two-fluid model has been found to be a direct result of driver behavior, and can also be used to represent behavioral aspects of driver populations, e.g., aggressiveness, passiveness, etc. Through these behavioral aspects they can also be related to safety on roadways. Due to which the two-fluid model can be considered to be a safety footprint for a particular road or individual driver. Due to which it is critical to understand factors that influence the two-fluid model. In this study, two-fluid models were estimated using naturalistic driving data collected with GPS data loggers in San Luis Obispo (SLO), California. Linear referencing in ArcMap was used to link the GPS data with roadway characteristic data for each element of the roadway network. The linear referencing methodology is the key to relate the GPS driving data with the elements of roadway network. This study explores two fundamental questions: (1) how sensitive are the estimates of the two fluid parameters to various samples? This question is fundamentally important to help define the integrity of the two-fluid model for planning and operational purposes. To this end we use a random sampling approach to address this question. (2) Are there behavioral differences across gender? This provides important behavioral insights on driving behavior across gender. Significant differences were observed between male and female drivers, with female drivers being more aggressive.


      PubDate: 2015-01-15T13:53:20Z
       
  • Evaluation and spatial analysis of automated red-light running enforcement
           cameras
    • Abstract: Publication date: January 2015
      Source:Transportation Research Part C: Emerging Technologies, Volume 50
      Author(s): Mohamed M. Ahmed , Mohamed Abdel-Aty
      Red light cameras may have a demonstrable impact on reducing the frequency of red light running violations; however, their effect on the overall safety at intersections is still up for debate. This paper examined the safety impacts of Red Light Cameras (RLCs) on traffic crashes at signalized intersections using the Empirical Bayes (EB) method. Data were obtained from the Florida Department of Transportation for twenty-five RLC equipped intersections in Orange County, Florida. Additional fifty intersections that remained with no photo enforcement in the vicinity of the treated sites were collected to examine the spillover effects on the same corridors. The safety evaluation was performed at three main levels; only target approaches where RLCs were installed, all approaches on RLC intersections, and non-RLC intersections located on the same travel corridors as the camera equipped intersections. Moreover, the spatial spillover effects of RLCs were also examined on an aggregate level to evaluate the safety impacts on driver behavior at a regional scale. The results from this study indicated that there was a consistent significant reduction in angle and left-turn crashes and a significant increase in rear-end crashes on target approaches, in addition, the magnitude and the direction of these effects, to a lesser degree, were found similar on the whole intersection. Similar trends in shift of crash types were spilled-over to non-RLC intersections in the proximity of the treated sites. On an aggregate county level, there was a moderate spillover benefits with a notable crash migration to the boundary of the county.


      PubDate: 2015-01-15T13:53:20Z
       
  • Estimating risk effects of driving distraction: A dynamic errorable
           car-following model
    • Abstract: Publication date: January 2015
      Source:Transportation Research Part C: Emerging Technologies, Volume 50
      Author(s): Jay Przybyla , Jeffrey Taylor , Jason Jupe , Xuesong Zhou
      This paper aims to estimate the risk effects of distracted driving, by incorporating a dynamic, data-driven car-following model in an algorithmic framework. The model was developed to predict the situational risk associated with distracted driving. To obtain longitudinal driving patterns, this paper analyzed and synthesized the NGSIM naturalistic driver and traffic database, through a dynamic time warping algorithm, to identify essential driver behavior and characteristics. Cognitive psychology concepts, distracted driving simulator, and experimental data were adapted to examine the probabilistic nature of distracted driving due to internal vehicle distractions. An extended microscopic car-following model was developed and validated, which can be fully integrated with the naturalistic data and incorporate the probabilities of driver distraction.


      PubDate: 2015-01-15T13:53:20Z
       
  • Methodology for safety improvement programming using constrained
           network-level optimization
    • Abstract: Publication date: January 2015
      Source:Transportation Research Part C: Emerging Technologies, Volume 50
      Author(s): Jackeline Murillo-Hoyos , Nathee Athigakunagorn , Samuel Labi
      This paper develops and implements a decision support framework that prescribes and prioritizes cost-effective safety improvements at deserving locations under funding constraints, economic and comprehensive crash cost methods, at rural two-lane highway sections. The framework is demonstrated using Indiana’s 7700-mile rural two-lane network. For sections that are both deficient and hazardous under unconstrained budget and economic crash cost method, it was determined that $55M is needed. Assuming a safety budget of $1M/year over a 5-year period, it was found that 170–180 crashes (translating to $8–15M) could be prevented. If the annual budget is increased to $2M/year over a 5-year period, 244 crashes (translating to $12–26M) can be prevented. Monetary amounts are in Year 2000 constant dollars. Overall, the results suggest that perpetual increases in highway safety improvements spending are not likely to be accompanied by a commensurate reduction of crashes at rural two-lane highways. In other words, there is a ceiling to the effectiveness of engineering safety countermeasures, and therefore non-engineering countermeasures such as safety education and enforcement must be sought to complement the engineering efforts at rural two-lane highways.


      PubDate: 2015-01-15T13:53:20Z
       
  • A probabilistic approach towards a crash risk assessment of urban segments
    • Abstract: Publication date: January 2015
      Source:Transportation Research Part C: Emerging Technologies, Volume 50
      Author(s): Sara Ferreira , António Couto
      This paper presents a probabilistic approach to measure the crash risk associated to an urban segment. This approach leads to a hotspot definition and identification using a probabilistic model defining the dependent variable as an indicator of a discrete choice. A binary choice model is used considering a binary dependent variable that differentiates a hotspot from a safe site set by the number of crashes per year per kilometre. The explanatory variables to set similar segments are based on average annual daily traffic, segment length, density of minor intersections. A threshold value for the number of crashes per kilometre is set to distinguish hotspots from safe sites. Based on this classification, a binary model is applied that allows the construction of an ordered site list using the probability of a site being a hotspot. A demonstration of the proposed methodology is provided using urban segment data from Porto, Portugal, covering a five-year period. The results of the binary model show a good fit. To evaluate and compare the probabilistic method with three usual hotspot identification methods described in the Highway Safety Manual, measures are used to test the performance of each method. Depending on the tests, actual data or simulated input, which are usually considered to set the “true” hotspots, were used. In general, the tests results indicate that the binary model performs better than the other three models. Nevertheless, it should be noted that the probabilistic approach provides an outcome that is quite different from the other methods, thus making difficult to ensure a linear comparison with the other methods. Overall, the study shows an alternative to hotspot identification using a risk measure in which the gains are the simplicity, the reliability, and the efficiency of model outcome.


      PubDate: 2015-01-15T13:53:20Z
       
  • Exploring the feasibility of classification trees versus ordinal discrete
           choice models for analyzing crash severity
    • Abstract: Publication date: January 2015
      Source:Transportation Research Part C: Emerging Technologies, Volume 50
      Author(s): Ghazan Khan , Andrea R. Bill , David A. Noyce
      A cross-median crash (CMC) is one of the most severe types of crashes in which a vehicle crosses the median and sometimes collides with opposing traffic. A study of severity of CMCs in the state of Wisconsin was conducted by Lu et al. in 2010. Discrete choice models, namely ordinal logit and probit models were used to analyze factors related to the severity of CMCs. Separate models were developed for single and multi-vehicle CMCs. Although 25 different crash, roadway, and geometric variables were used, only 3 variables were found to be statistically significant which were alcohol usage, posted speed, and road conditions. The objective of this research was to explore the feasibility of GUIDE Classification Tree method to analyze the severity of CMCs to discover if any additional information could be revealed. A dataset of CMCs in the state of Wisconsin between 2001 and 2007, used in the study by Lu et al. was used to develop three different GUIDE Classification Trees. Additionally, the effects of variable types (continuous or discrete), misclassification costs, and tree pruning characteristics on models results were also explored. The results were directly compared with discrete choice models developed in the study by Lu et al. showing that the GUIDE Classification Trees revealed new variables (median width and traffic volume) that affect CMC severity and provided useful insight on the data. The results of this research suggest that the use of Classification Tree analysis should at least be considered in conjunction with regression-based crash models to better understand factors affecting crashes. Classification Tree models were able to reveal additional information about the dependent variable and offer advantages with respect to multicollinearity and variable redundancy issues.


      PubDate: 2015-01-15T13:53:20Z
       
  • Crash frequency analysis of left-side merging and diverging areas on urban
           freeway segments – A case study of I-75 through downtown Dayton,
           Ohio
    • Abstract: Publication date: January 2015
      Source:Transportation Research Part C: Emerging Technologies, Volume 50
      Author(s): Deogratias Eustace , Aline Aylo , Worku Y. Mergia
      This paper analyzes the effect of left- and right-side merging and diverging areas and other variables such as light condition, roadway pavement condition, drivers’ age and presence of construction work zones on the occurrence frequency of crashes. A 6.5-mile (10.5-km) section of I-75 that passes through downtown Dayton, Ohio was considered. The area of interest has a high traffic volume and consists of different geometric design challenges including closely spaced merging and diverging ramps. A four-year record of crash data (2005–2008) and a statistical modeling technique that assumes a negative binomial distribution on generalized linear models (GLMs) were used to develop separate models for merging and diverging areas. The model results show that left-side merging and diverging areas are critical elements in crash frequency in the vicinity of ramps on freeways. In addition, pavement condition, light condition, and work zones were found to be significant predictors of crash frequency. Specifically, the results indicate that crashes are about 7.88 times more likely to occur on merging areas located on the left side of the freeway lanes compared to those on the right. For diverging areas, about 2.26 times more crashes are likely to occur near diverging areas on the left compared to those diverging on the right side of the freeway. In addition, adverse pavement conditions (such as wet pavement, snow, and ice), adverse light conditions (such as darkness and glare), and presence of work zone were found to be significant variables in the occurrence of crashes.


      PubDate: 2015-01-15T13:53:20Z
       
  • A correlated random parameter approach to investigate the effects of
           weather conditions on crash risk for a mountainous freeway
    • Abstract: Publication date: January 2015
      Source:Transportation Research Part C: Emerging Technologies, Volume 50
      Author(s): Rongjie Yu , Yingge Xiong , Mohamed Abdel-Aty
      Freeway crashes are highly influenced by weather conditions, especially for a mountainous freeway affected by adverse weather conditions. In order to reduce crash occurrence, a variety of weather monitoring systems and Intelligent Transportation Systems (ITS) have been introduced to address the weather impact. However, the effects of weather conditions on crash occurrence have not been fully investigated and understood. With detailed weather information from weather monitoring stations, this study seeks to investigate the complex effects of weather factors, such as visibility and precipitation, on crash occurrence based on safety performance functions. Unlike conventional traffic safety studies which deal with crash frequency, crash rates per 100million vehicle miles travelled were adopted as the dependent variable in this study. Three years of weather related crash data from a 15mile mountainous freeway on I-70 in Colorado were utilized. First, a fixed parameter Tobit model was estimated to unveil the effects of explanatory variables on crash rates. Then, in order to characterize the heterogeneous effects of weather conditions across the homogeneous segments, a traditional random parameter Tobit model was developed. Furthermore, for the purpose of monitoring the intricate interactions between weather conditions and geometric characteristics, a multivariate structure for the distribution of random parameters was introduced; which result in a correlated random parameter Tobit model. Likelihood ratio test results demonstrated that the correlated random parameter Tobit model was superior to the uncorrelated random parameter and fixed parameter Tobit models. Moreover, visibility and precipitation variables were found to have substantial correlations with geometric characteristics like steep downgrade slopes and curve segments. Results from the models will shed lights on future applications of weather warning systems to improve traffic safety.


      PubDate: 2015-01-15T13:53:20Z
       
  • Development and evaluation of an enhanced surrogate safety assessment
           framework
    • Abstract: Publication date: January 2015
      Source:Transportation Research Part C: Emerging Technologies, Volume 50
      Author(s): Jaehyun (Jason) So , George Dedes , Byungkyu Brian Park , Siavash HosseinyAlamdary , Dorota Grejner-Brzezinsk
      This study adopted an integrated simulation approach for generating more realistic vehicle trajectories, ultimately for enhancing the surrogate safety assessment methodology under the Connected Vehicle (CV) environment. This integrated simulation divides into two main parts, real time-based simulation approach and post-processing approach. The real-time simulation environment consists of the microscopic traffic simulator to generate various traffic situations, driver warning simulator, GPS/INU simulator, and V2V/V2I communication delays probability model. The post-processing approach includes vehicle dynamics model to incorporate vehicle dynamics to the vehicle trajectories and Surrogate Safety Assessment Model (SSAM) to identify traffic conflicts. This integrated simulation approach was adopted to assess the safety impact of Connected Vehicle (CV)-based traffic applications by considering potential positioning errors and communication delays which are likely to occur in reality. The evaluation results showed that the V2V/V2I communication delays degraded the effectiveness of driver warnings by 3–13% while the driver warnings under ideal conditions (i.e., error-free vehicle positions and no V2V/V2I communication delays) reduced conflicts by 27–42%. In addition, the most accurate GPS/INU device (i.e., Real-Time Kinematic (RTK) GPS) was the best for use with vehicle safety applications as the RTK case was the closest to the ground truth-based warning scenario. Meanwhile, the device with the lowest accuracy (i.e., autonomous GPS) was not very suitable for deployment in the safety application as this case showed even worse results than the base case (i.e., no driver warnings). This integrated simulation approach used for these experiments is a practical and reliable alternative for assessing the safety impact of CV-based traffic applications since it considers the potential positioning errors and communication delays which are likely to affect the performance of CV-based traffic applications in reality and uses vehicle dynamics-incorporated vehicle trajectories which are more realistic than the sore traffic simulator vehicle trajectories.


      PubDate: 2015-01-15T13:53:20Z
       
  • Inter-national benchmarking of road safety: State of the art
    • Abstract: Publication date: January 2015
      Source:Transportation Research Part C: Emerging Technologies, Volume 50
      Author(s): Yongjun Shen , Elke Hermans , Qiong Bao , Tom Brijs , Geert Wets , Wuhong Wang
      Road traffic injuries and fatalities have nowadays been recognized as one of the most important public health issues that requires concerted efforts for effective and sustainable prevention. Given the fact that more and more countries are taking steps to improve their road safety situation, there is a growing need for these countries to work together more closely, because there are quite a number of common problems that can be identified in close cooperation, and improvement can be expected by learning lessons from existing best practices in other countries. As a consequence, comparison between a range of countries in terms of their road safety performance and development or – using state-of-the-art terminology – inter-national benchmarking of road safety, is currently widely advocated by most countries and international bodies as an emerging methodology for road safety improvement. However, performing a successful road safety benchmarking practice is by no means easy. Challenges exist from the definition of benchmarking framework at the very beginning to the final decisions in terms of identification of best practices and establishment of a continuous process of mutual learning. In this paper, the theoretical background of the benchmarking approach is introduced, and a specific benchmarking cycle for road safety is established which consists of five core activities. Moreover, as a valuable benchmarking tool, the development of a road safety index is highlighted, and some theoretical and practical issues on this subject are discussed.
      Graphical abstract image Highlights

      PubDate: 2015-01-15T13:53:20Z
       
  • Simulating vehicle dynamics on both design plans and laser-scanned road
           geometry to guide highway design policy
    • Abstract: Publication date: January 2015
      Source:Transportation Research Part C: Emerging Technologies, Volume 50
      Author(s): Alexander Brown , Sean Brennan
      Increasingly, roadway designers use simulations to analyze how roadway design choices affect vehicle dynamics and ultimately safety. When using commercial multi-body simulations for analysis of vehicle dynamics, engineers are usually able to trust that the vehicle states predicted by simulations are reasonably accurate. This is because simulation software companies spend significant research and development dollars making sure that vehicle models and numerical solvers give realistic results. However, when using vehicle dynamic simulations for the analysis of roadway designs, the road environment must be defined by the user. Researchers are often left to wonder whether the roads they simulate in software are representative of what construction crews actually built in the field. This paper compares the results of simulations using both a road’s design geometry, i.e., the CAD plans, versus a three-dimensional point-cloud scan of its actual geometry. For this comparison, high-fidelity commercial vehicle simulation software (CarSim and TruckSim) was used. Research-grade sensing equipment allowed for the digitization of road geometries during highway traversals in the field to create a simulated mesh of the real highway geometry. After comparing simulation results for traversals of design geometry and measured road geometry with collected vehicle data, the road safety implications of discrepancies seen between the predicted and measured vehicle states are also discussed.


      PubDate: 2015-01-15T13:53:20Z
       
  • Design and evaluation of a user-centered interface to model scenarios on
           driving simulators
    • Abstract: Publication date: January 2015
      Source:Transportation Research Part C: Emerging Technologies, Volume 50
      Author(s): Ghasan Bhatti , Roland Brémond , Jean-Pierre Jessel , Nguyen-Thong Dang , Fabrice Vienne , Guillaume Millet
      Modeling scenarios on driving simulators is a complex and difficult task for end-users because they do not have the skills necessary to program the scenarios. In this paper, we present a user-centered architecture in which we have split the scenario modeling interface into 3 sub-interfaces (Template Builder, Experiment Builder, Experiment Interface) based on the user skill. The concept is tested with a panel of end-users, with fair results in terms of performance and subjective judgment.


      PubDate: 2015-01-15T13:53:20Z
       
  • The impact of mobile phone distraction on the braking behaviour of young
           drivers: A hazard-based duration model
    • Abstract: Publication date: January 2015
      Source:Transportation Research Part C: Emerging Technologies, Volume 50
      Author(s): Md. Mazharul Haque , Simon Washington
      Braking is a crucial driving task with a direct relationship with crash risk, as both excess and inadequate braking can lead to collisions. The objective of this study was to compare the braking profile of young drivers distracted by mobile phone conversations to non-distracted braking. In particular, the braking behaviour of drivers in response to a pedestrian entering a zebra crossing was examined using the CARRS-Q Advanced Driving Simulator. Thirty-two licensed drivers drove the simulator in three phone conditions: baseline (no phone conversation), hands-free, and handheld. In addition to driving the simulator, each participant completed questionnaires related to driver demographics, driving history, usage of mobile phones while driving, and general mobile phone usage history. The drivers were 18–26years old and split evenly by gender. A linear mixed model analysis of braking profiles along the roadway before the pedestrian crossing revealed comparatively increased decelerations among distracted drivers, particularly during the initial 20kph of deceleration. Drivers’ initial 20kph deceleration time was modelled using a parametric accelerated failure time (AFT) hazard-based duration model with a Weibull distribution with clustered heterogeneity to account for the repeated measures experiment design. Factors found to significantly influence the braking task included vehicle dynamics variables like initial speed and maximum deceleration, phone condition, and driver-specific variables such as licence type, crash involvement history, and self-reported experience of using a mobile phone whilst driving. Distracted drivers on average appear to reduce the speed of their vehicle faster and more abruptly than non-distracted drivers, exhibiting excess braking comparatively and revealing perhaps risk compensation. The braking appears to be more aggressive for distracted drivers with provisional licenses compared to drivers with open licenses. Abrupt or excessive braking by distracted drivers might pose significant safety concerns to following vehicles in a traffic stream.


      PubDate: 2015-01-15T13:53:20Z
       
  • Editorial Board
    • Abstract: Publication date: January 2015
      Source:Transportation Research Part C: Emerging Technologies, Volume 50




      PubDate: 2015-01-15T13:53:20Z
       
  • Road Safety Technologies
    • Abstract: Publication date: January 2015
      Source:Transportation Research Part C: Emerging Technologies, Volume 50
      Author(s): Andrea Benedetto , Fabrizio D’Amico



      PubDate: 2015-01-15T13:53:20Z
       
  • An evaluation of section control based on floating car data
    • Abstract: Publication date: Available online 7 January 2015
      Source:Transportation Research Part C: Emerging Technologies
      Author(s): Mario Vanlommel , Maarten Houbraken , Pieter Audenaert , Steven Logghe , Mario Pickavet , Philippe De Maeyer
      Floating Car Data (FCD) consists of positional information from moving vehicles and is ideally suited to monitor traffic conditions in large road networks. Given a large mobile fleet equipped with the FCD-system, FCD allows to determine actual travel times on road segments/links and determine traffic state. Based on this link-specific information, we analyse the effectiveness of section control, also called average speed control, on 2 Belgian highways. Section control systems measure the travel time of vehicles between different positions to determine the speed limit compliance. Results show that the section control systems reduce speed limit violations over the entire length of the system, contrary to the local effect of fixed traffic cameras. Section control systems also reduce speed differences between vehicles in the same section as the speed dispersion is much smaller compared to similar, uncontrolled parts of the highway.


      PubDate: 2015-01-15T13:53:20Z
       
  • Speed limits, speed selection and network equilibrium
    • Abstract: Publication date: February 2015
      Source:Transportation Research Part C: Emerging Technologies, Volume 51
      Author(s): Hai Yang , Hongbo Ye , Xinwei Li , Bingqing Zhao
      This paper investigates the local and global impact of speed limits by considering road users’ non-obedient behavior in speed selection. Given a link-specific speed limit scheme, road users will take into account the subjective travel time cost, the perceived crash risk and the perceived ticket risk as determinant factors for their actual speed choice on each link. Homogeneous travelers’ perceived crash risk is positively related to their driving speed. When travelers are heterogeneous, the perceived crash risk is class-specific: different user classes interact with each other and choose their own optimal speed, resulting in a Nash equilibrium speed pattern. With the speed choices on particular roads, travelers make route choices, resulting in user equilibrium in a general network. An algorithm is proposed to solve the user equilibrium problem with heterogeneous users under link-specific speed limits. The models and algorithms are illustrated with numerical examples.


      PubDate: 2015-01-15T13:53:20Z
       
  • Exploring association between perceived importance of travel/traffic
           information and travel behaviour in natural disasters: A case study of the
           2011 Brisbane floods
    • Abstract: Publication date: February 2015
      Source:Transportation Research Part C: Emerging Technologies, Volume 51
      Author(s): Zuduo Zheng , Jinwoo (Brian) Lee , Mohammad Saifuzzaman , Jian Sun
      A sound understanding of travellers’ behavioural changes and adaptation when facing a natural disaster is a key factor in efficiently and effectively managing transport networks at such times. This study specifically investigates the importance of travel/traffic information and its impact on travel behaviour during natural disasters. Using the 2011 Brisbane flood as a case study, survey respondents’ perceptions of the importance of travel/traffic information before, during, and after the flood were modelled using random-effects ordered logit. A hysteresis phenomenon was observed: respondents’ perceptions of the importance of travel/traffic information increased during the flood, and although its perceived importance decreased after the flood, it did not return to the pre-flood level. Results also reveal that socio-demographic features (such as gender and age) have a significant impact on respondents’ perceptions of the importance of travel/traffic information. The roles of travel time and safety in a respondent’s trip planning are also significantly correlated to their perception of the importance of this information. The analysis further shows that during the flood, respondents generally thought that travel/traffic information was important, and adjusted their travel plans according to information received. When controlling for other factors, the estimated odds of changing routes and cancelling trips for a respondent who thought that travel/traffic information was important, are respectively about three times and seven times the estimated odds for a respondent who thought that travel/traffic information was not important. In contrast, after the flood, the influence of travel/traffic information on respondents’ travel behaviour diminishes. Finally, the analysis shows no evidence of the influence of travel/traffic information’s on respondents’ travel mode; this indicates that inducing travel mode change is a challenging task.


      PubDate: 2015-01-15T13:53:20Z
       
  • The influence of in-vehicle speech warning timing on drivers’
           collision avoidance performance at signalized intersections
    • Abstract: Publication date: February 2015
      Source:Transportation Research Part C: Emerging Technologies, Volume 51
      Author(s): Xuedong Yan , Yuting Zhang , Lu Ma
      Collision warning systems have been identified as an effective technique for avoiding accidents. In such a system, the delivery time of warning messages is a crucial factor that influences the success of collision avoidance. This study therefore contributes by providing experimental analyses on a range of delivery times of warning messages, which has been overlooked in past studies. Using simulator-based techniques, experimental scenarios are specifically designed for accounting the red-light-running events at intersections and drivers are recruited to test on different settings of warning timings. Several measures including brake reaction time, alarm-to-brake-onset time and deceleration are adopted as reflections of drivers’ performances under the collision avoidance process and they are connected to several factors by mixed effect models. According to the results, the collision warning system actually can largely reduce the occurrence of red-light-running collisions, more importantly it reveals the influence of warning timings within the predefined ranges and 4.0s or 4.5s may be a proper warning timing for the right-angle collisions accused by red-light-running vehicles in this study. Besides, effects from directional information embedded in warning messages are also investigated in this study. Findings are important to the design of collision warning systems especially in the aspect of warning timings.


      PubDate: 2015-01-15T13:53:20Z
       
  • Variable speed limit control for severe non-recurrent freeway bottlenecks
    • Abstract: Publication date: February 2015
      Source:Transportation Research Part C: Emerging Technologies, Volume 51
      Author(s): Danjue Chen , Soyoung Ahn
      Variable speed limit (VSL) schemes are developed based on the Kinematic Wave theory to increase discharge rates at severe freeway bottlenecks induced by non-recurrent road events such as incidents or work zones while smoothing speed transition. The main control principle is to restrict upstream demand (in free-flow) progressively to achieve three important objectives: (i) to provide gradual speed transition at the tail of an event-induced queue, (ii) to clear the queue around the bottleneck, and (iii) to discharge traffic at the stable maximum flow that can be sustained at the bottleneck without breakdown. These control objectives are accomplished without imposing overly restrictive speed limits. We further provide remedies for (a) underutilized bottleneck capacity due to underestimated stable maximum flow and (b) a re-emergent queue at the bottleneck due to an overestimated stable maximum flow. We analytically formulate the reductions in total delay in terms of control parameters to provide an insight into the system performance and sensitivity. The results from the parameter analysis suggest that significant delay savings can be realized with the proposed VSL control strategies.


      PubDate: 2015-01-15T13:53:20Z
       
  • Operation of signalized diamond interchanges with frontage roads using
           dynamic reversible lane control
    • Abstract: Publication date: February 2015
      Source:Transportation Research Part C: Emerging Technologies, Volume 51
      Author(s): Jing Zhao , Yue Liu , Xiaoguang Yang
      Signalized diamond interchanges (SDI), connecting major highways and surface streets in urban and suburban areas, are probably the most widely used interchange patterns. The limited storage space between the two closely joined intersections coupled with heavy traffic volumes may easily oversaturate the facility and cause spillback problems, especially with the presence of frontage roads. This paper presents an innovative design and operational model for SDI by dynamically reversing certain lanes in the internal link on a regular basis with the deployment of overhead reversible lane control signs. A Binary-Mixed-Integer-Linear-Program (BMILP) is formulated to simultaneously optimize lane markings, dynamic usage of the reversible lane, and signal timings for the new SDI system. Results from extensive numerical analyses reveal the promising property of the proposed design and operational model in expanding capacity and reducing congestion at the SDI with frontage roads.


      PubDate: 2015-01-15T13:53:20Z
       
  • Classification of Automatic Radar Plotting Aid targets based on improved
           Fuzzy C-Means
    • Abstract: Publication date: February 2015
      Source:Transportation Research Part C: Emerging Technologies, Volume 51
      Author(s): Feng Ma , Qing Wu , Xinping Yan , Xiumin Chu , Di Zhang
      Maritime ARPA, Automatic Radar Plotting Aid, systems often complicate navigation by mistaking channel structures and land objects for vessels in inland rivers and harbors. By using Fuzzy C-Means (FCM), it is possible to construct an artificial intelligence to classify and identify ARPA target types and calculate the possibility of a target being a real vessel based on the target’s speed over ground, vector over ground, and location. The membership functions of each attribute are constructed using statics, expert knowledge, and electronic chart information. The main difficulty in developing a successful FCM framework to achieve the previously stated goals is the determination of a proper method of calculating the classification number C and fuzzy coefficient m. Because the value of C for the case of ARPA targets classification is finite, the best C would be determined by assessing the Euclidean distance. The value of m is related to the discreteness of the evidence and results, which is evaluated using the Shannon entropy and the gain. A number of methods exist to properly evaluate the contributions from different forms of evidence so that the best m can be found using the tendentiousness of the evidence. In field testing, the improved FCM was able to accurately classify the ARPA targets, decrease the workload on the ship’s officer, and increase safety.


      PubDate: 2015-01-15T13:53:20Z
       
  • Discovering temporal changes in hierarchical transportation data: Visual
           analytics & text reporting tools
    • Abstract: Publication date: February 2015
      Source:Transportation Research Part C: Emerging Technologies, Volume 51
      Author(s): John Alexis Guerra-Gómez , Michael L. Pack , Catherine Plaisant , Ben Shneiderman
      Analyzing important changes to massive transportation datasets like national bottleneck statistics, passenger data for domestic flights, airline maintenance budgets, or even publication data from the Transportation Research Record can be extremely complex. These types of datasets are often grouped by attributes in a tree structure hierarchy. The parent–child relationships of these hierarchical datasets allow for unique analytical opportunities, including the ability to track changes in the dataset at different levels of granularity, over time or between versions. For example, analysts can use hierarchies to uncover changes in the patterns of passengers flying in the United States over the last ten years, breaking down the data by states, cities, airports, and number of passengers. Exploring changes in travel patterns over time can help carriers make better decisions regarding their operations and long-range planning. This paper describes TreeVersity2, a web-based data comparison tool that provides users with information visualization techniques to find what has changed in a dataset over time. TreeVersity2 enables users to explore data that can be inherently hierarchical or not (by categorizing them by their attributes). An interactive textual reporting tool complements the visual exploration when the amount of data is very large. The results of two case studies conducted with transportation domain experts along with the results of an exit questionnaire are also described. TreeVersity2 preloaded with several demo datasets can be found at (http://treeversity.cattlab.umd.edu) along with several example videos.


      PubDate: 2015-01-15T13:53:20Z
       
  • An enhanced SPSA algorithm for the calibration of Dynamic Traffic
           Assignment models
    • Abstract: Publication date: February 2015
      Source:Transportation Research Part C: Emerging Technologies, Volume 51
      Author(s): Lu Lu , Yan Xu , Constantinos Antoniou , Moshe Ben-Akiva
      Simultaneous perturbation stochastic approximation (SPSA) is an efficient and well established optimization method that approximates gradients from successive objective function evaluations. It is especially attractive for high-dimensional problems and has been successfully applied to the calibration of Dynamic Traffic Assignment (DTA) models. This paper presents an enhanced SPSA algorithm, called Weighted SPSA (W-SPSA), which incorporates the information of spatial and temporal correlation in a traffic network to limit the impact of noise and improve convergence and robustness. W-SPSA appears to outperform the original SPSA algorithm by reducing the noise generated by uncorrelated measurements in the gradient approximation, especially for DTA models of sparsely correlated large-scale networks and a large number of time intervals. Comparisons between SPSA and W-SPSA have been performed through rigorous synthetic tests and the application of W-SPSA for the calibration of real world DTA networks is demonstrated with a case study of the entire expressway network in Singapore.


      PubDate: 2015-01-15T13:53:20Z
       
  • Rapid estimation of electric vehicle acceptance using a general
           description of driving patterns
    • Abstract: Publication date: February 2015
      Source:Transportation Research Part C: Emerging Technologies, Volume 51
      Author(s): Michael A. Tamor , Paul E. Moraal , Briana Reprogle , Miloš Milačić
      A reliable estimate of the potential for electrification of personal automobiles in a given region is dependent on detailed understanding of vehicle usage in that region. While broad measures of driving behavior, such as annual miles traveled or the ensemble distribution of daily travel distances are widely available, they cannot be predictors of the range needs or fuel-saving potential that influence an individual purchase decision. Studies that record details of individual vehicle usage over a sufficient time period are available for only a few regions in the US. In this paper we compare statistical characterization of four such studies (three in the US, one in Germany) and find remarkable similarities between them, and that they can be described quite accurately by properly chosen set of distributions. This commonality gives high confidence that ensemble data can be used to predict the spectrum of usage and acceptance of alternative vehicles in general. This generalized representation of vehicle usage may also be a powerful tool in estimating real-world fuel consumption and emissions.


      PubDate: 2015-01-15T13:53:20Z
       
  • Introducing specific power to bicycles and motorcycles: Application to
           electric mobility
    • Abstract: Publication date: February 2015
      Source:Transportation Research Part C: Emerging Technologies, Volume 51
      Author(s): Magno Mendes , Gonçalo Duarte , Patricia Baptista
      Electric bicycles and motorcycles have emerged as a possible way of improving the transportation system sustainability. This work’s aim was to quantify the energy consumption, the trip travel and the driving dynamics on specific routes in Lisbon, Portugal. Six electric and conventional bicycles and motorcycles were monitored, and a methodology to quantify the power required in each driving second was developed: Motorcycle and Bicycle Specific Power (MSP and BSP respectively). MSP and BSP allows characterizing energy consumption rates based on on-road data and to define real-world operation patterns (driving power distribution), as well as to benchmark the different propulsion technologies under the same baseline of specific power. For negative MSP and BSP modes, the conventional and the electric motorcycles and bicycles demonstrated a similar pattern. However, their behavior was different for positive modes, since electric technologies allow reaching higher power conditions. The methodology developed estimates accurately the energy consumption (average deviation of −0.19±6.76% for motorcycles and of 1.41±8.91% for bicycles). The MSP and BSP methodologies were tested in 2 Lisbon routes. For the electric motorcycle an increase in trip time (+36%) was observed when compared to the conventional one, while for the electric bicycle a 9.5% decrease was verified when compared to the conventional one. The Tank-to-Wheel (TTW) energy consumption for motorcycles was reduced by 61% when shifting to electric mobility, while a 30% Well-to-Wheel (WTW) reduction is obtained. For the electric bicycles, an additional energy use is quantified due to the battery electricity consumption.


      PubDate: 2015-01-15T13:53:20Z
       
  • Motorway speed pattern identification from floating vehicle data for
           freight applications
    • Abstract: Publication date: February 2015
      Source:Transportation Research Part C: Emerging Technologies, Volume 51
      Author(s): A. Pascale , F. Deflorio , M. Nicoli , B. Dalla Chiara , M. Pedroli
      Nowadays, the diffusion of in-car navigators, location-enabled smartphones and various reasons for tracking vehicles – either for insurance and recovery, fleet management or for electronic tolling – are making floating car data (FCD) a leading solution for traffic monitoring. In the next years, this solution might be much more strengthened by the introduction and diffusion of black boxes, installed on commercial or private vehicles devoted to monitor or validate new safety technologies (e.g., the automatic in-vehicle emergency call service eCall in Europe). 1 More details can be found on the official website of the European Commission for Mobility and Transport, http://ec.europa.eu/transport/road_safety/specialist/knowledge/esave/esafety_measures_known_safety_effects/black_boxes_in_vehicle_data_recorders_en.htm, and of the European Parliament, http://www.europarl.europa.eu/sides/getDoc.do?pubRef=-//EP//TEXT+PV+20140225+ITEM-013+DOC+XML+V0//EN. For eCall see Directive 2010/40/EU of the European Parliament and of the Council of 7 July 2010, on the framework for the deployment of Intelligent Transport Systems in the field of road transport and for interfaces with other modes of transport, 6.8.2010, and Commission Delegated Regulation (EU) No 305/2013, of 26 November 2012, supplementing Directive 2010/40/EU of the European Parliament and of the Council with regard to the harmonised provision for an interoperable EU-wide eCall. 1 FCD, possibly integrated with data coming from infrastructure-based monitoring systems, represents a valuable platform for intelligent transport systems (ITS). Traffic monitoring based on FCD relies on a processing algorithm for aggregating the measured data into an accurate and complete traffic map. In this paper we present an experimental study on FCD processing based on a unique large amount of data in Italy, provided by heavy-duty vehicles used as probes over the Italian A4 motorway. A processing procedure is proposed for identifying the typical speed patterns, to be used as baseline for automatic anomaly detection, transport planning or traffic analysis applications. A first assessment based on real traffic-event information shows that the comparison of the probe data to previously identified historical speed patterns allows a clear detection of anomalous events.


      PubDate: 2015-01-15T13:53:20Z
       
  • Modelling shared space users via rule-based social force model
    • Abstract: Publication date: February 2015
      Source:Transportation Research Part C: Emerging Technologies, Volume 51
      Author(s): Bani Anvari , Michael G.H. Bell , Aruna Sivakumar , Washington Y. Ochieng
      The promotion of space sharing in order to raise the quality of community living and safety of street surroundings is increasingly accepted feature of modern urban design. In this context, the development of a shared space simulation tool is essential in helping determine whether particular shared space schemes are suitable alternatives to traditional street layouts. A simulation tool that enables urban designers to visualise pedestrians and cars trajectories, extract flow and density relation in a new shared space design, achieve solutions for optimal design features before implementation, and help getting the design closer to the system optimal. This paper presents a three-layered microscopic mathematical model which is capable of representing the behaviour of pedestrians and vehicles in shared space layouts and it is implemented in a traffic simulation tool. The top layer calculates route maps based on static obstacles in the environment. It plans the shortest path towards agents’ respective destinations by generating one or more intermediate targets. In the second layer, the Social Force Model (SFM) is modified and extended for mixed traffic to produce feasible trajectories. Since car movements are not as flexible as pedestrian movements, velocity angle constraints are included for cars. The conflicts described in the third layer are resolved by rule-based constraints for shared space users. An optimisation algorithm is applied to determine the interaction parameters of the force-based model for shared space users using empirical data. This new three-layer microscopic model can be used to simulate shared space environments and assess, for example, new street designs.


      PubDate: 2015-01-15T13:53:20Z
       
  • Extending Time to Collision for probabilistic reasoning in general traffic
           scenarios
    • Abstract: Publication date: February 2015
      Source:Transportation Research Part C: Emerging Technologies, Volume 51
      Author(s): James R. Ward , Gabriel Agamennoni , Stewart Worrall , Asher Bender , Eduardo Nebot
      Vehicle-to-vehicle communication systems allow vehicles to share state information with one another to improve safety and efficiency of transportation networks. One of the key applications of such a system is in the prediction and avoidance of collisions between vehicles. If a method to do this is to succeed it must be robust to measurement uncertainty and to loss of communication links. The method should also be general enough that it does not rely on constraints on vehicle motion for the accuracy of its predictions. It should work for all interactions between vehicles and not just a select subset. This paper presents a method to calculate Time to Collision for unconstrained vehicle motion. This metric is gated using a novel technique based on relative vehicle motion that we call “looming”. Finally, these ideas are integrated into a probabilistic framework that accounts for uncertainty in vehicle state and loss of vehicle-to-vehicle communication. Together this work represents a new way of considering vehicle collision estimation. These algorithms are validated on data collected from real world vehicle trials.


      PubDate: 2015-01-15T13:53:20Z
       
  • Dynamic system optimal model for multi-OD traffic networks with an
           advanced spatial queuing model
    • Abstract: Publication date: February 2015
      Source:Transportation Research Part C: Emerging Technologies, Volume 51
      Author(s): Kien Doan , Satish V Ukkusuri
      This paper provides an approach to solve the system optimal dynamic traffic assignment problem for networks with multiple O–D pairs. The path-based cell transmission model is embedded as the underlying dynamic network loading procedure to propagate traffic. We propose a novel method to fully capture the effect of flow perturbation on total system cost and accurately compute path marginal cost for each path. This path marginal cost pattern is used in the projection algorithm to equilibrate the departure rate pattern and solve the system optimal dynamic traffic assignment. We observe that the results from projection algorithm are more reliable than those from method of successive average algorithm (MSA). Several numerical experiments are tested to illustrate the benefits of the proposed model.


      PubDate: 2015-01-15T13:53:20Z
       
  • A hybrid approach to integrate fuzzy C-means based imputation method with
           genetic algorithm for missing traffic volume data estimation
    • Abstract: Publication date: February 2015
      Source:Transportation Research Part C: Emerging Technologies, Volume 51
      Author(s): Jinjun Tang , Guohui Zhang , Yinhai Wang , Hua Wang , Fang Liu
      Although various innovative traffic sensing technologies have been widely employed, incomplete sensor data is one of the most major problems to significantly degrade traffic data quality and integrity. In this study, a hybrid approach integrating the Fuzzy C-Means (FCM)-based imputation method with the Genetic Algorithm (GA) is develop for missing traffic volume data estimation based on inductance loop detector outputs. By utilizing the weekly similarity among data, the conventional vector-based data structure is firstly transformed into the matrix-based data pattern. Then, the GA is applied to optimize the membership functions and centroids in the FCM model. The experimental tests are conducted to verify the effectiveness of the proposed approach. The traffic volume data collected at different temporal scales were used as the testing dataset, and three different indicators, including root mean square error, correlation coefficient, and relative accuracy, are utilized to quantify the imputation performance compared with some conventional methods (Historical method, Double Exponential Smoothing, and Autoregressive Integrated Moving Average model). The results show the proposed approach outperforms the conventional methods under prevailing traffic conditions.


      PubDate: 2015-01-15T13:53:20Z
       
  • Vehicle detection based on And–Or Graph and Hybrid Image Templates
           for complex urban traffic conditions
    • Abstract: Publication date: February 2015
      Source:Transportation Research Part C: Emerging Technologies, Volume 51
      Author(s): Ye Li , Fei-Yue Wang
      In complex urban traffic conditions, occlusions among vehicles and between vehicles and non-vehicle objects are very common, which presents a major challenge to current vehicle detection methods. To circumvent this problem, we have proposed a vehicle detection method based on an And–Or Graph (AOG) and Hybrid Image Templates (HITs). In our AOG, the vehicle object is hierarchically decomposed into multiple vehicle parts by up–down and left–right division to reduce the impacts of vehicle occlusion. Furthermore, the vehicle parts are modeled by HITs to differentiate vehicles from non-vehicle objects effectively. These HITs integrate multiple features including sketch, texture, color and flatness so as to well describe the vehicle features. To test the performance of the proposed method, we have conducted a quantitative experiment and a comparison experiment. The experimental results show that, by combining AOG and HIT for vehicle identification, severe occlusions among vehicles and non-vehicle objects under complex urban traffic environments can be dealt with efficiently. Furthermore, the results also indicated that our method can adapt to variations in vehicle poses and shapes.


      PubDate: 2015-01-15T13:53:20Z
       
  • Equity-based timetable synchronization optimization in urban subway
           network
    • Abstract: Publication date: February 2015
      Source:Transportation Research Part C: Emerging Technologies, Volume 51
      Author(s): Jianjun Wu , Muhan Liu , Huijun Sun , Tongfei Li , Ziyou Gao , David Z.W. Wang
      In the urban subway transportation system, passengers may have to make at least one transfer traveling from their origin to destination. This paper proposes a timetable synchronization optimization model to optimize passengers’ waiting time while limiting the waiting time equitably over all transfer station in an urban subway network. The model aims to improve the worst transfer by adjusting the departure time, running time, the dwelling time and the headways for all directions in the subway network. In order to facilitate solution, we develop a binary variables substitute method to deal with the binary variables. Genetic algorithm is applied to solve the problem for its practicality and generality. Finally, the suggested model is applied to Beijing urban subway network and several performance indicators are presented to verify the efficiency of suggested model. Results indicate that proposed timetable synchronization optimization model can be used to improve the network performance for transfer passengers significantly.


      PubDate: 2015-01-15T13:53:20Z
       
  • Evaluating a concept design of a crowd-sourced ‘mashup’
           providing ease-of-access information for people with limited mobility
    • Abstract: Publication date: December 2014
      Source:Transportation Research Part C: Emerging Technologies, Volume 49
      Author(s): Andrew May , Christopher J. Parker , Neil Taylor , Tracy Ross
      This study investigates the impact of using a concept map-based ‘mashup’ (www.accessadvisr.net) to provide volunteered (i.e. user contributed) ease of access information to travellers with limited mobility. A scenario-based user trial, centred around journey planning, was undertaken with 20 participants, divided equally between (1) those who have physical restrictions on their mobility, due to disability, illness or injury, and (2) those with practical mobility constraints due to being parents with young children who have to use a child’s pushchair when using public transport. Both user groups found the concept useful, but its potential impact was less for the pushchair user group. There were mixed views in relation to the ability of the mashup to convey the trustworthiness, credibility and reliability of information necessary for journey planning. The study identified a number of key information-related user requirements which help enable effective design of user contributed web-based resources for travellers with mobility-related issues.


      PubDate: 2014-12-05T14:52:34Z
       
  • Real time detection of driver attention: Emerging solutions based on
           robust iconic classifiers and dictionary of poses
    • Abstract: Publication date: December 2014
      Source:Transportation Research Part C: Emerging Technologies, Volume 49
      Author(s): G.L. Masala , E. Grosso
      Real time monitoring of driver attention by computer vision techniques is a key issue in the development of advanced driver assistance systems. While past work mostly focused on structured feature-based approaches, characterized by high computational requirements, emerging technologies based on iconic classifiers recently proved to be good candidates for the implementation of accurate and real-time solutions, characterized by simplicity and automatic fast training stages. In this work the combined use of binary classifiers and iconic data reduction, based on Sanger neural networks, is proposed, detailing critical aspects related to the application of this approach to the specific problem of driving assistance. In particular it is investigated the possibility of a simplified learning stage, based on a small dictionary of poses, that makes the system almost independent from the actual user. On-board experiments demonstrate the effectiveness of the approach, even in case of noise and adverse light conditions. Moreover the system proved unexpected robustness to various categories of users, including people with beard and eyeglasses. Temporal integration of classification results, together with a partial distinction among visual distraction and fatigue effects, make the proposed technology an excellent candidate for the exploration of adaptive and user-centered applications in the automotive field.


      PubDate: 2014-12-05T14:52:34Z
       
 
 
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