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Showing papers in "Transportation Research Record in 2007"


Journal ArticleDOI
TL;DR: A general model (minimizing overall braking induced by lane change, MOBIL) is proposed to derive lane-changing rules for discretionary and mandatory lane changes for a wide class of car-following models and allows one to vary the motivation for lane changing from purely egoistic to more cooperative driving behavior.
Abstract: A general model (minimizing overall braking induced by lane change, MOBIL) is proposed to derive lane-changing rules for discretionary and mandatory lane changes for a wide class of car-following models. Both the utility of a given lane and the risk associated with lane changes are determined in terms of longitudinal accelerations calculated with microscopic traffic models. This determination allows for the formulation of compact and general safety and incentive criteria for both symmetric and asymmetric passing rules. Moreover, anticipative elements and the crucial influence of velocity differences of these car-following models are automatically transferred to the lane-changing rules. Although the safety criterion prevents critical lane changes and collisions, the incentive criterion takes into account the advantages and disadvantages of other drivers associated with a lane change via the "politeness factor." The parameter allows one to vary the motivation for lane changing from purely egoistic to more c...

976 citations


Journal ArticleDOI
Abstract: This paper discusses the selection of indicators for comprehensive and sustainable transportation planning. It discusses the concept of sustainability and the role of indicators in planning, describes factors to consider in selecting indicators, identifies potential problems with conventional indicators, describes examples of indicators, and provides recommendations for selecting indicators for use in a particular situation.

434 citations


Journal ArticleDOI
TL;DR: In this paper, the results from a random phone survey of adults in the Portland, Oregon, region were used to explore the relationship between levels of cycling and demographics, objective environmental factors, perceptions of the environment, and attitudes.
Abstract: The levels of bicycling in the United States, particularly for nonrecreation purposes and among adults, are low. Only about 1% of the trips that people make in the United States are on bicycles, and less than 5% of trips under 1/2 mi are made on bicycles. Factors influencing the rates of cycling include demographics and environmental factors. Environmental factors can be measured both objectively (e.g., number of miles of bike lanes, average temperature, and street connectivity) and subjectively (e.g., people's ratings or perceptions of the bicycling environment). People's attitudes about travel and mobility likely play a role. This paper uses the results from a random phone survey of adults in the Portland, Oregon, region to explore the relationships between levels of cycling and demographics, objective environmental factors, perceptions of the environment, and attitudes. The survey revealed several significant differences, although additional analysis is necessary. Objective measures of proximity to off...

418 citations


Journal ArticleDOI
TL;DR: In this paper, the authors identified cost savings, convenient locations, and guaranteed parking as the most common motivations for carsharing use worldwide, and compared them with other car-sharing services.
Abstract: Carsharing (or short-term auto use) provides a flexible alternative that meets diverse transportation needs across the globe while reducing the negative impacts of private vehicle ownership. Although carsharing appeared in Europe between the 1940s and 1980s, the concept did not become popularized until the early 1990s. For nearly 20 years, worldwide participation in carsharing has been growing. Today, carsharing operates in approximately 600 cities around the world, in 18 nations and on 4 continents. Approximately 348,000 individuals share nearly 11,700 vehicles as part of organized carsharing services (>60% in Europe). Malaysia is operating a carsharing pilot, with a planned launch in 2007. Another eight countries are exploring carsharing. Thirty-three carsharing expert surveys were identified on an international basis. Cost savings, convenient locations, and guaranteed parking were identified as the most common motivations for carsharing use worldwide. An international comparison of carsharing operation...

317 citations


Journal ArticleDOI
TL;DR: In this paper, a new multivariate approach is introduced for jointly modeling data on crash counts by severity on the basis of multivariate Poisson-lognormal models, which can cope with both overdispersion and a fully general correlation structure in the data.
Abstract: A new multivariate approach is introduced for jointly modeling data on crash counts by severity on the basis of multivariate Poisson-lognormal models. Although the data on crash frequency by severity are multivariate in nature, they have often been analyzed by modeling each severity level separately, without taking into account correlations that exist among different severity levels. The new multivariate Poisson-lognormal regression approach can cope with both overdispersion and a fully general correlation structure in the data, as opposed to the recently suggested multivariate Poisson regression approach, which allows for neither overdispersion nor a general correlation structure in the data. The new method is applied to the multivariate crash counts obtained from intersections in California for 10 years. The results show promise toward the goal of obtaining more accurate estimates by accounting for correlations in the multivariate crash counts and overdispersion.

305 citations


Journal ArticleDOI
TL;DR: For example, this paper found that after the introduction of City CarShare in the San Francisco, Bay area in California, 29% of carshare members had gotten rid of one or more cars, and 4.8% of members' trips and 5.4% of their vehicle miles traveled were in carshare vehicles.
Abstract: Four years after the introduction of City CarShare in the San Francisco, Bay area in California, 29% of carshare members had gotten rid of one or more cars, and 4.8% of members' trips and 5.4% of their vehicle miles traveled were in carshare vehicles. Matched-pair comparisons with a statistical control group suggest that, over time, members have reduced total vehicular travel. However, most declines occurred during the first 1 to 2 years of the program; 3 to 4 years after City CarShare's inauguration, earlier declines had leveled off. Because many carshare vehicles are small and fuel-efficient but can carry several people, the trend in per capita gasoline consumption also is downward. Mindful of the cumulative costs of driving, carshare members appear to have become more judicious and selective when deciding whether to drive, take public transit, walk, bike, or even forgo a trip. Coupled with reduced personal car ownership, these factors have given rise to a resourceful form of automobility in the San Fra...

278 citations


Journal ArticleDOI
TL;DR: The car can be integrated into the complex structures of contemporary lifestyles like no other mode of transportation as discussed by the authors and the consequence is the emergence of highly car-dependent mobility behavior, which is referred to as multimodals.
Abstract: The car can be integrated into the complex structures of contemporary lifestyles like no other mode of transportation. The consequence is the emergence of highly car-dependent mobility behavior. Nevertheless, the use of multiple modes of transportation, a behavior that is desirable from the perspective of transportation policy, is a matter of course and daily routine for a not insignificant segment of the population. This group, referred to as multimodals, is the subject of this study. "Multimodality" is defined as the use of at least two modes of transportation—bicycle, car, or public transportation—in 1 week. Monomodal car users serve as the contrast group for the study. The study is based on the data sets from the national survey Mobility in Germany, 2002, as well as the 1999-2004 data of the German Mobility Panel. The results indicate a close relationship between multimodality and life stage. Most adolescents are multimodal, mainly out of necessity, and the percentage of multimodal people declines dra...

240 citations


Journal ArticleDOI
TL;DR: Models of the duration of lane changes are presented using detailed vehicle trajectory data collected in naturalistic driving with high-mounted video cameras for passenger cars and heavy vehicles and statistical tests are conducted for the similarity between the lane-change durations of the two vehicle types.
Abstract: Lane changes significantly affect the characteristics of traffic flow. Lane-changing models are therefore important in microscopic traffic simulation. Existing lane-changing models emphasize the decision-making aspects of the task but generally neglect the detailed modeling of the lane-changing action itself and model it only as an instantaneous event. However, research indicates that lane-changing durations are on average in the range of 5 to 6 s. The omission of lane-changing durations from simulation models may have a significant impact on simulation outputs. Models of the duration of lane changes are presented. These models are estimated by using detailed vehicle trajectory data that were collected in naturalistic driving with high-mounted video cameras. Separate models are presented for passenger cars and for heavy vehicles and statistical tests are conducted for the similarity between the lane-change durations of the two vehicle types.

236 citations


Journal ArticleDOI
TL;DR: In this article, a survey of the Icelandic pavement industry showed strong support for WMA technology use to improve cool weather paving, and two projects in Maryland showing the potential for widespread adoption of high reclaimed asphalt-pavement mixtures.
Abstract: Warm-mix asphalt (WMA) describes a range of technologies that seek to lower emissions and reduce energy consumption by lowering the temperature at which asphalt mixtures are produced and placed. Despite these benefits, reduced mixture viscosity may be the most likely reason for widespread adoption of WMA technologies. Hot-mix asphalt (HMA) producers are unlikely to adopt WMA technologies solely to lower emissions, because current environmental regulations and the relatively clean nature of HMA plants make lower emissions unnecessary and unprofitable except in select air pollution areas. Producers are also unlikely to adopt WMA technologies solely to reduce energy consumption, because energy savings are less than the associated costs except in the most expensive energy markets. Reduced viscosity makes the best business case for widespread WMA technology adoption, because this benefit offers cost and risk reduction: it can (a) alleviate compaction problems associated with cool weather, (b) reduce compaction equipment needs at the job site, and (c) lower the risk of poor compaction when working with stiff mixtures. This conclusion is supported by basic economic calculations, a survey of the Icelandic pavement industry showing strong support for WMA technology use to improve cool weather paving, and two projects in Maryland showing the potential for WMA technology use to lower the risk of poor compaction of high reclaimed asphalt-pavement mixtures.

216 citations


Journal ArticleDOI
TL;DR: In this article, the chemical and physical bonding mechanisms associated with selected nontraditional stabilizers were investigated and the results of the experiments were used to improve the understanding of how these non-traditional additives stabilize soils.
Abstract: Because of the high cost of quality construction materials, transportation engineers are often forced to seek alternative designs using substandard materials, commercial construction aids, alternative pavement materials, and innovative design practices. Nontraditional soil stabilization additives are being marketed as viable solutions for stabilizing marginal materials as a low-cost alternative to traditional construction materials. Nontraditional additives are diverse in their composition and the way they interact with soil. Unfortunately, little is known about their interaction with geotechnical materials and their fundamental stabilization mechanisms. The objective of this research was to advance current understanding of the chemical and physical bonding mechanisms associated with selected nontraditional stabilizers. The research consisted of conducting qualitative analyses of hypothesized stabilization mechanisms, examining historical literature for supporting documentation, and performing laboratory experiments to improve the understanding of how these nontraditional additives stabilize soils. Laboratory experiments included image analyses, physical characterization, and chemical analyses to determine the primary constituents of the mineral, soil, stabilizer, and stabilized soil composite. The focus of this effort was to provide insight into the proposed mechanisms by using the laboratory data to examine proposed mechanisms from the historical literature and to provide additional hypotheses for the interaction between nontraditional additives and different soil types.

213 citations


Journal ArticleDOI
TL;DR: In this article, a methodology was developed to project growth trends of the motor vehicle population and associated oil demand and carbon dioxide (CO2) emissions in China through 2050 through three scenarios of vehicle growth by following different patterns of motor vehicle growth in Europe and Asia.
Abstract: During this study a methodology was developed to project growth trends of the motor vehicle population and associated oil demand and carbon dioxide (CO2) emissions in China through 2050. In particular, the numbers of highway vehicles, motorcycles, and rural vehicles were projected under three scenarios of vehicle growth by following different patterns of motor vehicle growth in Europe and Asia. Projections showed that by 2030 China could have more highway vehicles than the United States has today. Three scenarios of vehicle fuel economy were also developed on the basis of current and future policy efforts to reduce vehicle fuel consumption in China and in developed countries. With the vehicle population projections and potential vehicle fuel economy data, it was projected that in 2050 China's on-road vehicles could consume approximately 614 million to 1,016 million metric tons of oil (or 12.4 million to 20.6 million barrels per day) and emit 1.9 billion to 3.2 billion metric tons (or 2.1 billion to 3.5 bi...

Journal ArticleDOI
TL;DR: This article evaluated the stopping characteristics of vehicles 2.5 to 5.5 s upstream of signalized intersections at the start of a yellow interval, a region typically considered drivers' indecision zone or dilemma zone.
Abstract: A field study evaluated the stopping characteristics of vehicles 2.5 to 5.5 s upstream of signalized intersections at the start of a yellow interval, a region typically considered drivers' indecision zone or dilemma zone. Characteristics included brake-response times for first-to-stop vehicles, deceleration rates for first-to-stop vehicles, distinguishing characteristics and prediction of first-to-stop versus last-to-go events, and distinguishing characteristics and prediction of red-light-running events. Consumergrade video cameras temporarily installed at four high-speed and two lowspeed intersections in the Madison, Wisconsin, area recorded dilemma zone vehicles. Several factors were measured for each last-to-go (n = 435) and first-to-stop (n = 463) vehicle in each lane during each yellow interval, including approach speed; distance upstream at start of yellow; brake-response time; deceleration rate; vehicle type; headway; tailway; action of vehicles in adjacent lanes; presence of side-street vehicles,...

Journal ArticleDOI
Søren Underlien Jensen1
TL;DR: The Danish Road Directorate sponsored a study to develop methods for objectively quantifying pedestrian and bicyclist stated satisfaction with road sections between intersections as mentioned in this paper, which provided a measure of how well urban and rural roads accommodate pedestrian and bicycle travel.
Abstract: The Danish Road Directorate sponsored a study to develop methods for objectively quantifying pedestrian and bicyclist stated satisfaction with road sections between intersections. The results provide a measure of how well urban and rural roads accommodate pedestrian and bicycle travel. To determine how existing traffic operations, geometric conditions, and other variables affect pedestrians' and bicyclists' satisfaction, 407 randomly selected Danes were shown video clips from 56 roadway segments filmed by a pedestrian walking and a bicyclist riding along the road. Respondents rated the roadway segments on a six-point scale ranging from very dissatisfied to very satisfied. This resulted in 7,724 pedestrian ratings and 7,596 bicyclist ratings. Roadway segments and video clips were described by 150 variables. Pedestrian and bicyclist satisfaction models were developed by cumulative logit regression of the ratings and the variables. The models included variables that related significantly (p ≤ .05) to the sat...

Journal ArticleDOI
TL;DR: Two techniques are presented for real-time measurement of vehicledelay and queue length at a signalized intersection, and these automated delay and queue estimates are compared with manually ground-truthed measurement.
Abstract: Vehicle delay and queue length are quantitative measures of intersection performance. The technological advancement in the field of vehicle sensors and traffic controllers has reached a point where it has enabled efficient measurement of these performance measures. Two techniques are presented for real-time measurement of vehicle delay and queue length at a signalized intersection, and these automated delay and queue estimates are compared with manually ground-truthed measurement. These techniques were evaluated at an instrumented intersection in Noblesville, Indiana. The root-mean-square error by both techniques was below 0.7 veh-s for estimation of average delay and less than 0.15 vehicle for estimation of average maximum queue length, both on a cycle-by-cycle basis.

Journal ArticleDOI
TL;DR: A video-based vehicle detection and classification (VVDC) system was developed for truck data collection using wide-ranging available surveillance cameras and the accuracy for vehicle detection was above 97%, and the total truck count error was lower than 9% for all three tests, indicating that the video image processing method developed is indeed a viable alternative for Truck data collection.
Abstract: Length-based vehicle classification data are important inputs for traffic operation, pavement design, and transportation planning. However, such data are not directly measurable by single-loop detectors, the most widely deployed type of traffic sensor in the existing roadway infrastructure. In this study a video-based vehicle detection and classification (VVDC) system was developed for truck data collection using wide-ranging available surveillance cameras. Several computer vision-based algorithms were developed or applied to extract background image from a video sequence, detect presence of vehicles, identify and remove shadows, and calculate pixel-based vehicle lengths for classification. Care was taken to handle robustly negative effects resulting from vehicle occlusions in the horizontal direction and slight camera vibrations. The pixel-represented lengths were exploited to distinguish long vehicles from short vehicles; hence the need for complicated camera calibration can be eliminated. These algorithms were implemented in the prototype VVDC system using Microsoft Visual C#. As a plug-and-play system, the VVDC system is capable of processing both digitized image streams and live video signals in real time. The system was tested at three test locations under different traffic and environmental conditions. The accuracy for vehicle detection was above 97%, and the total truck count error was lower than 9% for all three tests. This indicates that the video image processing method developed for vehicle detection and classification in this study is indeed a viable alternative for truck data collection.

Journal ArticleDOI
TL;DR: In this paper, surface free energy of asphalt binders and aggregates was used to derive energy parameters that quantify the moisture sensitivity of various combinations of materials, including asphalt-aggregate interactions.
Abstract: Conventional methods to quantify the moisture sensitivity of asphalt mixtures are based on the comparison of mechanical properties of the mix before and after a moisture-conditioning process. Although this approach consolidates the effect of material and mixture properties on moisture sensitivity, it does not identify the causes responsible for the poor or good performance of the mixture. In this study, surface free energy of asphalt binders and aggregates was used to derive energy parameters that quantify the moisture sensitivity of various combinations of materials. The moisture sensitivity of 12 asphalt mixtures carefully designed to represent a wide range of asphalt-aggregate interactions was measured in the laboratory under controlled conditions. Test results indicate that the moisture sensitivity of these mixtures correlates well with the energy parameters, which are based on the surface energy properties of the constituent materials. Incorporating the specific surface area of the aggregate into the...

Journal ArticleDOI
TL;DR: Warm-mix asphalt (WMA) mixes produced by an emulsion process were evaluated under accelerated loading in three total sections of the National Center for Asphalt Technology Test Track and used as the surface mix for two of the sections.
Abstract: Warm-mix asphalt (WMA) mixes produced by an emulsion process were evaluated under accelerated loading in three total sections of the National Center for Asphalt Technology Test Track and used as the surface mix for two of the sections. Evotherm was incorporated into the same mixes used previously on the track. In-place densities of the WMA surface layers were equal to or better than the hot-mix asphalt (HMA) surface layers, even when compaction temperatures were reduced by 8°C to 42°C (15°F to 75°F). Laboratory rutting-susceptibility tests conducted in the asphalt pavement analyzer indicated similar performance for the WMA and HMA surface mixes with the PG 67-22 base asphalt. However, laboratory tests indicated an increased potential for moisture damage with the WMA mixes. The two WMA sections and the HMA section showed excellent rutting performance in the field after the application of 515,333 equivalent single-axle loads in a 43-day period. One of the WMA sections was also evaluated for quick turnover to traffic and showed good performance.

Journal ArticleDOI
TL;DR: A v-support vector machine (v-SVM) model, which has the particular strength of overcoming local minima and overfitting common to neural network models, is proposed for short-term traffic volume prediction and outperforms the MLFNN model for all data sets.
Abstract: Predictions for short-term traffic volume provide important inputs for traveler information and traffic management. Traffic volumes in the near future are often estimated based on historical volumes. Because of the complicated nonlinear relationship between historical and future traffic volume data, many previous studies used neural networks to predict short-term traffic volumes. In this research, a v-support vector machine (v-SVM) model, which has the particular strength of overcoming local minima and overfitting common to neural network models, is proposed for short-term traffic volume prediction. The v-SVM model is compared with a widely used multilayer feed-forward neural network (MLFNN) model using four data sets collected from three interstate freeways. Testing results show that for both one-step and two-step forecasting, the v-SVM model outperforms the MLFNN model for all data sets in terms of mean absolute percentage error and root-mean-square error. Key issues in applying both models are also dis...

Journal ArticleDOI
TL;DR: In this paper, a model of crash risk based on the distribution of in-vehicle glances is described, as well as several characteristics of the traffic environment, and experimental data collected in a driving simulator are used to demonstrate how an analysis of the average glance durations to an invehicle display might lead to different conclusions about safety compared with an alternative analysis of a tail end of the distribution.
Abstract: In general, the unsafe conditions that are likely to produce a motor vehicle crash reside not at the mean of a given distribution (in other words, under typical conditions), but rather in the tails of the distribution. For example, an unusually slow response to a traffic obstacle, rather than an average response, may result in a collision. Although that situation means that crashes are the exception and not the norm, it has implications for how safety-critical data are approached and handled. In this current paper, experimental data collected in a driving simulator are used to demonstrate how an analysis of the average glance durations to an in-vehicle display might lead to different conclusions about safety compared with an alternative analysis of the tail end of the distribution. In addition, a model of crash risk based on the distribution of in-vehicle glances is described, as well as several characteristics of the traffic environment.

Journal ArticleDOI
TL;DR: Results show that forecasts obtained from recursive adaptive filtering methods are comparable with those from maximum likelihood estimated models, and the adaptive methods deliver this performance at a significantly lower computational cost.
Abstract: Conventionally, most traffic forecasting models have been applied in a static framework in which new observations are not used to update model parameters automatically. The need to perform periodic parameter reestimation at each forecast location is a major disadvantage of such models. From a practical standpoint, the usefulness of any model depends not only on its accuracy but also on its ease of implementation and maintenance. This paper presents an adaptive parameter estimation methodology for univariate traffic condition forecasting through use of three well-known filtering techniques: the Kalman filter, recursive least squares, and least mean squares. Results show that forecasts obtained from recursive adaptive filtering methods are comparable with those from maximum likelihood estimated models. The adaptive methods deliver this performance at a significantly lower computational cost. As recursive, self-tuning predictors, the adaptive filters offer plug-and-play capability ideal for implementation in...

Journal ArticleDOI
TL;DR: In this article, an integrated general purpose data collection module that timestamps detector and phase state changes within a National Electrical Manufacturers Association actuated traffic signal controller was developed to provide quantitative graphs to assess arterial progression, phase capacity utilization, movement delay, and served volumes on a cycle-by-cycle basis.
Abstract: Cycle-by-cycle data have been shown to be effective in the analysis of a signalized intersection with measures of effectiveness such as volume-to-capacity ratios, arrival type, and average vehicular delay. Currently, actuated traffic controllers are unable to store vehicle counts and vehicle occupancy in cycle-by-cycle bins, requiring extra equipment and personnel to collect data in these bins. The objective of this research was to develop an integrated general purpose data collection module that timestamps detector and phase state changes within a National Electrical Manufacturers Association actuated traffic signal controller and uses those data to provide quantitative graphs to assess arterial progression, phase capacity utilization, movement delay, and served volumes on a cycle-by-cycle basis. Given that the United States recently received a grade of 61 of 100 on the National Traffic Signal Report Card, it is particularly important that procedures such as these be used to provide performance measures ...

Journal ArticleDOI
TL;DR: In this article, rheological properties of two commonly used performance grade (PG) binders (PG 64-22 and PG 70-28) were evaluated, with and without Sasobit and Aspha-Min additives.
Abstract: Warm-mix asphalt (WMA), which reduces the production temperatures (mixing and compaction) while maintaining the advantages of hot-mix asphalt (HMA), is becoming an attractive paving material. In this study, rheological properties of two commonly used performance grade (PG) binders (PG 64-22 and PG 70-28) were evaluated, with and without Sasobit and Aspha-Min additives. For PG 64-22, 2%, 3%, and 4% Sasobit additive reduced the mixing temperature of the pure binder from 163°C to 147°C (i.e., by 16°C). In case of the PG 70-28, the reductions are 10°C, 12°C and 13°C, respectively, for 2%, 3%, and 4% Sasobit additive. No significant decrease in mixing temperature by the Aspha-Min additive was observed in using the rotational viscometer. Evaluation of the binders on the basis of G*/sin(δ) demonstrates no negative effect on high-temperature grading due to high-temperature viscosity reduction. With the addition of 4% Sasobit additive, the high-temperature binder grading of PG 64 (actually PG 65) increases to PG 6...

Journal ArticleDOI
TL;DR: In this article, the authors explored the weather-ridership relationship and its potential applications in transit operations and planning using the Chicago Transit Authority (CTA) in Illinois as a case study, investigating the impact of five weather elements (temperature, rain, snow, wind, and fog) on daily bus and rail ridership and variation across modes, day types, and seasons.
Abstract: This paper explores the weather-ridership relationship and its potential applications in transit operations and planning. Using the Chicago Transit Authority (CTA) in Illinois as a case study, the paper investigates the impact of five weather elements (temperature, rain, snow, wind, and fog) on daily bus and rail ridership and variation across modes, day types, and seasons. The resulting relationships are applied to the CTA ridership trend analysis, showing how preliminary findings may change after controlling for weather. The paper emphasizes the importance of having a theoretical framework encompassing weather and travel.

Journal ArticleDOI
TL;DR: In this paper, the authors evaluated several mathematical models to calculate the onset of tertiary flow for asphalt mixtures, which is a significant parameter in evaluating rutting in the field.
Abstract: The objective of this research study was to evaluate several mathematical models to be used in calculating the onset of tertiary flow [referred to as the flow number (FN) parameter] for asphalt mixtures. The FN indicates the onset of shear deformation in asphalt mixtures, which is a significant parameter in evaluating rutting in the field. The FN is obtained from the repeated load permanent deformation (RLPD) laboratory test. Current modeling techniques in determining the FN use a polynomial model fitting approach, which works well for most conventional asphalt mixtures. However, analysis and observations on the use of this polynomial model for rubber-modified asphalt mixtures showed problems in identifying the true FN values. The scope of the work included the collection and analysis of more than 300 RLPD test data files, which comprised more than 40 mixtures, a wide range of test temperatures, and several stress levels. A new comprehensive mathematical model was recommended to accurately determine the F...

Journal ArticleDOI
TL;DR: The goal of this research is to develop a method for automated analysis of road safety with video sensors to address the problem of dependency on the deteriorating collision data and address the main shortcomings of the traffic conflict technique.
Abstract: Traffic safety analysis has often been undertaken with historical collision data. However, well-recognized availability and quality problems are associated with collision data. In addition, the use of collision records for safety analysis is reactive: a significant number of collisions has to be recorded before action is taken. Therefore, the observation of traffic conflicts has been advocated as a complementary approach in the analysis of traffic safety. However, incomplete conceptualization and the cost of training observers and collecting conflict data have been factors inhibiting extensive application of the traffic conflict technique. The goal of this research is to develop a method for automated analysis of road safety with video sensors to address the problem of dependency on the deteriorating collision data. The method automates the extraction of traffic conflicts from video sensor data. This method should address the main shortcomings of the traffic conflict technique. A comprehensive system is described for traffic conflict detection in video data. The system is composed of a feature-based vehicle tracking algorithm adapted for intersections and a traffic conflict detection method based on the clustering of vehicle trajectories. The clustering uses a K-means approach with hidden Markov models and a simple heuristic to find the number of clusters automatically. Traffic conflicts can then be detected by identifying and adapting pairs of models of conflicting trajectories. The technique is demonstrated on real-world video sequences of traffic conflicts.

Journal Article
TL;DR: The Swissmetro European Market Study as mentioned in this paper evaluated technology, market conditions, European policy, investment costs, and risks associated with the project, and concluded that there is not sufficient market potential for the SwissMetro system in European long-distance transport.
Abstract: Results of the Swissmetro European Market Study are presented. Swissmetro is a proposed high-speed passenger ground transportation system that would operate magnetically levitated trains in underground tunnels with reduced air pressure by using linear motor technology. The market study considered the market feasibility of constructing Swissmetro on potential European corridors. It evaluated technology, market conditions, European policy, investment costs, and risks associated with the project. The study conclusion was that there is not sufficient market potential for the Swissmetro system in European long-distance transport. The main problems with Swissmetro identified in the study were the long time necessary to bring the technology to commercial deployment; the lack of obvious corridors (most high-demand corridors will be served by high-speed rail by 2020); strong competition from other modes, such as air and high-speed rail; European Union policy of supporting an interoperable system of rail lines; Swissmetro’s high capital and operating costs—plus the risk that these costs may be significantly underestimated—and Swissmetro’s long construction time.

Journal ArticleDOI
TL;DR: The SPF developed for this research indicates that, for the same traffic volume, rural frontage road segments experience about the same number of severe crashes as typical rural two-lane highways.
Abstract: In some states, frontage roads are frequently used along freeway and fully controlled principal arterial corridors. Their primary function is to provide access between the arterial, or freeway, and adjacent developed property. Little information about the safety performance of rural frontage roads exists. This paper describes the development of a safety performance function (SPF) and accident modification factors (AMFs) for rural frontage road segments. Both one-way and two-way frontage road operations are addressed. The AMFs quantify the relationship between specific changes in geometric design and road safety. The findings from this research show that wider lanes and shoulders are associated with a reduction in segment-related collisions. In addition, the data suggest that the presence of edge marking has an impact on rural two-way frontage road safety. The SPF developed for this research indicates that, for the same traffic volume, rural frontage road segments experience about the same number of severe crashes as typical rural two-lane highways.

Journal ArticleDOI
TL;DR: The stochastic approach provides new measures of traffic flow performance based on aspects of traffic reliability and provides a quantitative assessment for oversaturated conditions.
Abstract: A stochastic concept for highway capacity analysis is presented. The capacity of a highway facility is regarded as a random variable instead of a constant value. Thus, the stochastic approach provides new measures of traffic flow performance based on aspects of traffic reliability. A method for the estimation of capacity distribution functions from empirical data based on statistical methods for lifetime data analysis is introduced. This method is derived for the analysis of freeway capacity. However, the stochastic approach also is shown to be applicable to intersections. Results of the analysis of data samples from freeway sections in Germany indicate that freeway capacity is Weibull-distributed with a considerable variance. A Monte Carlo technique based on the stochastic description of capacity is proposed to quantify freeway traffic performance over a whole year. This technique also provides a quantitative assessment for oversaturated conditions.

Journal ArticleDOI
TL;DR: In this paper, the authors describe the key logistical issues that plagued the response to Hurricane Katrina, which in August 2005 devastated the US Gulf Coast, provide an example of the need to improve the efficiency of supply chains to the site of an extreme event.
Abstract: Extreme events pose serious logistical challenges to emergency and aid organizations active in preparation, response, and recovery operations, because the disturbances they produce have the potential to turn normal conditions suddenly into chaos Under these conditions, delivering critical supplies (eg, food, water, medical supplies) becomes an extremely difficult task because of the severe damage to the physical and virtual infrastructure and the limited or nonexistent transportation capacity In this context, the recovery process is made more difficult by the prevailing lack of knowledge about the nature and challenges of emergency supply chains As a result, the design of reliable emergency logistics systems is hampered by lack of knowledge about how formal and informal (emergent) supply chains operate and interact; methods to analyze and coordinate the flows of priority and nonpriority goods; and, in general, scientific methods to analyze logistics systems under extreme conditions This paper describes the key logistical issues that plagued the response to Hurricane Katrina The logistical failures following Katrina, which in August 2005 devastated the US Gulf Coast, provide an example of the need to improve the efficiency of supply chains to the site of an extreme event The paper is based on public accounts of the event and interviews conducted during a number of field visits to the Katrina-affected area in the aftermath of the event, as part of a research project funded by the National Science Foundation

Journal ArticleDOI
TL;DR: Validation results indicate that the new procedure can produce a synthetic population that more closely represents the true population than the conventional approach can.
Abstract: For the forecasting of activity-based travel demand, the representativeness of the base-year synthetic population is critical to the accuracy of subsequent simulation outcomes. To date, the conventional approach to synthesizing the base-year population has been based on the iterative proportional fitting procedure. Two issues associated with this conventional approach are discussed: the first is often termed as the zero-cell-value problem, and the second is related to the inability to control for statistical distributions of both household- and individual-level attributes. Then, a new population synthesis procedure is presented that addresses the limitations of the conventional approach. The new procedure is implemented into an operational software system and used to generate synthetic populations for the Dallas–Fort Worth area in Texas. Validation results indicate that the new procedure can produce a synthetic population that more closely represents the true population than the conventional approach can.