Showing papers in "Transportation Research Record in 2009"
TL;DR: It is proved in this paper that heterogeneity has a strong impact on the shape of the macroscopic fundamental diagram.
Abstract: Recently, some authors have provided experimental evidence of the existence of an urban-scale macroscopic fundamental diagram (MFD). Their convincing results were obtained on the basis of 500 urban fixed detectors placed 100 m upstream of most major intersections in the city of Yokohama, Japan. Those authors assume that the network in which data are collected is homogeneous in regard to congestion occurrence. This paper is devoted to exploring the impact of heterogeneity on the existence of an MFD. All data available for a medium-size French city are used. The data set encompasses measurements on highways, urban center streets (congested during business hours), and residential area streets. Data were collected by loop detectors with a distance from a downstream signal that can vary from 1,000 to 10 m. Heterogeneity is examined here in various aspects: differences between the surface and highway network, impact of the distance between the loop detector and the traffic signal in the surface network, and dif...
384 citations
TL;DR: In this article, the sensitivity of heart rate, skin conductance, and respiration rate as measures of mental workload in a simulated driving environment was examined, and the pattern of results indicates that physiological measures can be sensitive to changes in workload before the appearance of clear decrements in driving performance.
Abstract: This study examined the sensitivity of heart rate, skin conductance, and respiration rate as measures of mental workload in a simulated driving environment. Workload was systematically manipulated by using increasingly difficult levels of a secondary cognitive task. In a sample of 121 young adults, heart rate increased incrementally with increasing task demand. Significant elevations in skin conductance and respiration rate were also observed. At the lower levels of added workload, secondary task performance was nearly perfect and changes in indices of driving performance were negligible. At the highest level of workload, all three physiological measures appeared to plateau, and a subtle drop in simulated driving performance became detectable. Taken together, the pattern of results indicates that physiological measures can be sensitive to changes in workload before the appearance of clear decrements in driving performance. These findings further highlight a role for physiological monitoring as a means to measure mental workload in product design and functionality research. They also support work exploring the potential for incorporating physiological measures of driver workload and attentional state in future safety systems.
353 citations
TL;DR: A postprocessing procedure needing no input other than the most basic GPS raw data is described, which is applied to GPS records collected in the Swiss cities of Zurich, Winterthur, and Geneva to demonstrate that derived data are ready for further applications, such as discrete choice model estimations.
Abstract: Since the first Global Positioning System (GPS) studies in the mid-1990s, this method of surveying individual travel behavior has gained attention in transport research. Compared with classic travel survey methods, GPS studies offer researchers benefits of more accurate and reliable information. At the same time, the participants' burden is reduced substantially if the GPS data collection does not involve time-consuming questions. However, without additional information, such as modes and trip purposes, extensive postprocessing is required to derive data that can be used for analysis and model estimation. The corresponding procedures are an ongoing research issue. This paper describes a postprocessing procedure needing no input other than the most basic GPS raw data: three-dimensional positions and the corresponding time stamps. First, the data are thoroughly cleaned and smoothed. Second, trips and activities are determined. Third, the trips are segmented into single-mode stages, and the transport mode fo...
321 citations
TL;DR: In this paper, a web-based survey was conducted to understand the travel patterns and the specific issues regarding bicyclists on and around the campus of the University of Maryland, College Park.
Abstract: The focus of this study is on the opportunities and challenges presented to cyclists on and around the campus of the University of Maryland, College Park. A web-based survey was conducted to understand the travel patterns and the specific issues regarding bicyclists. The survey included questions about possible bicycle infrastructure improvements, policy, and program innovations to assess the perceptions of the campus community regarding these changes. The findings of this survey, conducted to understand cyclists' travel patterns and identify their issues and concerns, are discussed. Both nonbicycle commuters and bicycle commuters agreed that bicycle lanes, trails, and paths would encourage them to ride a bike (or ride more often) to the campus. Discrete choice models are estimated to model the commuters' mode to campus. The findings of the models suggest that people are more sensitive to time for nonmotorized modes and women are less likely to ride a bicycle. Those who perceive walking and biking as a form of exercise and identify flexibility of departure time as an important factor in their mode choice are more likely to ride a bicycle. Those more likely to choose to drive an automobile to campus assume that they do not have other options to commute to campus. Policies designed to promote the use of bicycle transportation on and to the campus based on these findings are presented. The results of this study will help practitioners and campus transportation planners understand the reasons that prevent people from bicycling and evaluate the transportation improvements that may be considered to achieve bicycle-friendly campuses.
286 citations
TL;DR: In this paper, the authors provide insight on gender differences with the factors that influence the decision to use a bicycle, with the intent of supporting policy development aimed at increasing bicycle ridership, particularly among women.
Abstract: Although men and women bicycle at relatively equal rates in industrialized countries such as the Netherlands, Germany, and Denmark, research has consistently found that in the United States men's total bicycle trips surpass women's by a ratio of at least 2 to 1 Current evidence, though limited, suggests that women are affected to greater or lesser degrees than men by certain factors The purpose of this study is to provide insight on gender differences with the factors that influence the decision to use a bicycle, with the intent of supporting policy development aimed at increasing bicycle ridership, particularly among women Bicycle use in six small cities in the western United States is examined to determine how gender interacts with individual factors and social and physical environments to influence bicycle behavior Analysis of data from an online survey using a binary logistic regression approach shows strong interaction of gender with individual factors such as safety perception and household resp
245 citations
TL;DR: In this paper, VISSIM, CMEM, and VISGAOST were linked to optimize signal timings and minimize fuel consumption and CO2 emissions in a 14-intersection network in Park City, Utah.
Abstract: One way to reduce excessive fuel consumption and vehicular emissions on urban streets is to optimize signal timings. Historically, signal timing optimization tools were used to reduce traffic delay and stops. The concept of optimizing signal timings to reduce fuel consumption and emissions was addressed decades ago with tools that are now considered outdated. This study advocates a fresh approach to integrating existing state-of-the-art tools for reassessing and ultimately minimizing fuel consumption and emissions. VISSIM, CMEM, and VISGAOST were linked to optimize signal timings and minimize fuel consumption and CO2 emissions. As a case study, a 14-intersection network in Park City, Utah, was used. Signal timings were optimized for seven optimization objective functions to find the lowest fuel consumption and CO2 emissions. Findings show that a formula commonly used to estimate fuel consumption in traffic simulation tools inadequately estimates fuel consumption and cannot be used as a reliable objective ...
208 citations
TL;DR: In this article, the authors evaluated the effect of road grade on vehicle fuel consumption (and thus carbon dioxide [CO2] emissions) and showed that road grade does have significant effects on the fuel economy of lig...
Abstract: Recently, advanced navigation systems have been developed that provide users the ability to select not only a shortest-distance route and even the shortest-duration route (on the basis of real-time traffic congestion information) but also routes that minimize fuel consumption as well as greenhouse gas and pollutant emissions. In these ecorouting systems, fuel consumption and emission attributes are estimated for roadway links on the basis of the measured traffic volume, density, and average speed. Instead of standard travel time or distance attributes, these link attributes are then used as cost factors when an optimal route for any particular trip is selected. In addition to roadway congestion attributes, road grade factors also have an effect on fuel consumption and emissions. This study evaluated the effect of road grade on vehicle fuel consumption (and thus carbon dioxide [CO2] emissions). The real-world experimental results show that road grade does have significant effects on the fuel economy of lig...
197 citations
TL;DR: This study is unique in its attempt to extract conflict indicators from video sequences in a fully automated way and provide detailed insight into the conflict process.
Abstract: Pedestrians are vulnerable road users, and despite their limited representation in traffic events, pedestrian-involved injuries and fatalities are overrepresented in traffic collisions. However, little is known about pedestrian exposure to the risk of collision, especially when compared with the amount of knowledge available for motorized traffic. More data and analysis are therefore required to understand the processes that involve pedestrians in collisions. Collision statistics alone are inadequate for the study of pedestrian-vehicle collisions because of data quantity and quality issues. Surrogate safety measures, as provided by the collection and study of traffic conflicts, were developed as a proactive complementary approach to offer more in-depth safety analysis. However, high costs and reliability issues have inhibited the extensive application of traffic conflict analysis. An automated video analysis system is presented that can (a) detect and track road users in a traffic scene and classify them ...
196 citations
TL;DR: A 10-year retrospective examines North America's carsharing evolution from initial market entry and experimentation (1994 to mid-2002) to growth and market diversification (mid-2002 to late 2007) to commercial mainstreaming (late 2007 to present).
Abstract: Carsharing (or short-term auto use) organizations provide members access to a fleet of shared vehicles on an hourly basis, reducing the need for private vehicle ownership. Since 1994, 50 carsharing programs have been deployed in North America—33 are operational and 17 defunct. As of July 1, 2008, there were 14 active programs in Canada and 19 in the United States, with approximately 319,000 carsharing members sharing more than 7,500 vehicles in North America. Another six programs were planned for launching in North America by January 2009. The four largest providers in the United States and Canada support 99% and 95.2% of total membership, respectively. A 10-year retrospective examines North America's carsharing evolution from initial market entry and experimentation (1994 to mid-2002) to growth and market diversification (mid-2002 to late 2007) to commercial mainstreaming (late 2007 to present). This evolution includes increased competition, new market entrants, program consolidation, increased market di...
190 citations
TL;DR: In this paper, the relationship between ridership and network design was studied by using updated graph theory concepts, and the authors showed that network topologies play a key role in attracting people to use public transit; ridership is not solely determined by cultural characteristics (North American versus European versus Asian) or city design (transit oriented versus automobile oriented).
Abstract: This paper demonstrates that network topologies play a key role in attracting people to use public transit; ridership is not solely determined by cultural characteristics (North American versus European versus Asian) or city design (transit oriented versus automobile oriented). The analysis considers 19 subway systems worldwide: those in Toronto, Ontario, Canada; Montreal, Quebec, Canada; Chicago, Illinois; New York City; Washington, D.C.; San Francisco, California; Mexico City, Mexico; London; Paris; Lyon, France; Madrid, Spain; Berlin; Athens, Greece; Stockholm, Sweden; Moscow; Tokyo; Osaka, Japan; Seoul, South Korea; and Singapore. The relationship between ridership and network design was studied by using updated graph theory concepts. Ridership was computed as the annual number of boardings per capita. Network design was measured according to three major indicators. The first is a measure of transit coverage and is based on the total number of stations and land area. The second relates to the maximum ...
173 citations
TL;DR: The application of complete journey data to bus network planning is used to illustrate the value of new information that would be available to network planners through the use of smart card fare payment data.
Abstract: This paper contributes to the emerging literature on the application of smart card fare payment data to public transportation planning. The research objective is to identify and assess complete, multimodal journeys using Oyster smart card fare payment data in London. Three transfer combinations (bus-to-Underground, Underground-to-bus, and bus-to-bus) are considered to formulate recommendations for maximum elapsed time thresholds to identify transfers between journey stages for each passenger on the London network. Recommended elapsed time thresholds for identifying transfers are 20 min for Underground-to-bus, 35 min for bus-to-Underground, and 45 min for bus-to-bus, but a range of values that account for variability across the network are also assessed. Key findings about bus and Underground travel in London include an average of 2.3 daily public transportation journeys per passenger, 1.3 journey stages per public transportation journey, and 23% of Underground journeys involving a transfer to or from a bu...
TL;DR: In this article, the authors evaluated the potential impact of secondary cognitive tasks on the allocation of drivers' visual attention and on vehicle control, and found that drivers were presented with increasingly complex forms of an auditory cognitive task while driving an instrumented vehicle.
Abstract: Cognitive distractions have been shown to affect drivers adversely and are a leading cause of accidents. Research indicates that drivers alter how they allocate their visual attention while engaging in secondary cognitive tasks. To evaluate the potential impact of secondary cognitive tasks on the allocation of drivers' visual attention and on vehicle control, drivers were presented with increasingly complex forms of an auditory cognitive task while driving an instrumented vehicle. Measures of vehicle performance and eye gaze were assessed. Consistent with theories of visual tunneling, gaze distributions were significantly smaller while drivers performed certain levels of the secondary task; peripheral vision was thereby reduced. During the most difficult level of the secondary task, gaze dispersion was smaller than during any other level of the task. Changes in visual attention may provide earlier indications of cognitive distraction than changes in vehicle control, the latter of which were observed only ...
TL;DR: In this paper, the effects of different fouling agents on ballast aggregate shear strength were studied at the University of Illinois using a large direct shear (shear box) device, and the strength properties of both clean and fouled ballast samples were determined when three types of fine materials (coal dust, plastic clayey soil, and mineral filler) were added to clean ballast sample under both dry and wet [mostly optimum moisture content (OMC)] conditions.
Abstract: Fouling refers to the condition of railroad ballast when voids in this unbound aggregate layer are filled with relatively finer materials or fouling agents, which commonly come from breakdown of the ballast aggregate, outside contamination such as coal dust from coal trains, or subgrade soil intrusion. Effects of different fouling agents on ballast aggregate shear strength were studied at the University of Illinois. Through the use of a large direct shear (shear box) device, the strength properties of both clean and fouled ballast samples were determined when three types of fine materials—coal dust, plastic clayey soil, and mineral filler—were added to clean ballast samples at various percentages by weight of ballast under both dry and wet [mostly optimum moisture content (OMC)] conditions. Realistic sample preparation procedures were conducted to closely simulate field-fouling scenarios. Test results showed that when the coal dust fouling percentage increased, the ballast shear strength steadily decreased. Wet fouling was found to exacerbate this trend. Results of ballast samples fouled with clay and mineral filler also showed decreasing trends in strength properties; however, coal dust was by far the worst fouling agent for its impact on track substructure and roadbed. Approximately 15% coal dust fouling by weight of ballast was statistically significant to cause considerable strength reductions. In the case of ballast fully fouled with wet coal dust at 35% OMC, the friction angles obtained were as low as the friction angle of coal dust itself.
TL;DR: In this paper, a real-time mathematical programming model of buses operating on a transit corridor that incorporates vehicle-capacity constraints is proposed, where two control policies are considered: (a) vehicle holding, which is applicable at any stop, and boarding limits that constrain the number of passengers entering a vehicle even when the vehicle is at less than physical capacity, to increase operating speed.
Abstract: A real-time mathematical programming model of buses operating on a transit corridor that incorporates vehicle-capacity constraints is proposed. The objective for the model is to minimize the total times experienced by all passengers in the system, from the moment they arrive at a stop to the moment they reach their destination. Two control policies are considered: (a) vehicle holding, which is applicable at any stop, and (b) boarding limits that constrain the number of passengers entering a vehicle even when the vehicle is at less than physical capacity, to increase operating speed. The objective function is quadratic, but not convex with linear constraints. This problem is solved by using MINOS in a reasonable amount of computation time. A case study in a high-demand scenario shows that the proposed control achieves reductions in the objective function of more than 22% and 12% compared with no control and only holding strategies, respectively.
TL;DR: A least-squares–based algorithm is developed to match measured delays in each cycle by using piecewise linear curves, which is useful for providing time-dependent intersection delay information to the driving public.
Abstract: Intersection delays are the major contributing factor to arterial delays. Methods to estimate intersection delay patterns by using measured travel times are studied. The delay patterns provide a way to estimate the delay for any vehicle arriving at the intersection at any time, which is useful for providing time-dependent intersection delay information to the driving public. The model requires sampled travel times between two consecutive locations on arterial streets, one upstream and the other downstream of a signalized intersection, without the need to know signal timing or traffic flow information. Signal phases can actually be estimated from the delay patterns, which is a unique feature of the proposed method in this paper. The proposed model is based on two observations regarding delays for signalized intersections: (a) delay can be approximately represented by piecewise linear curves due to the characteristics of queue forming and discharging and (b) there is a nontrivial increase in delay after the...
TL;DR: In this article, the authors used full Bayes multivariate Poisson lognormal models to estimate the expected crash frequency for different levels of crash severity and then compared those estimates to independent or univariate poisson Lognormal estimates.
Abstract: Traditionally, highway safety analyses have used univariate Poisson or negative binomial distributions to model crash counts for different levels of crash severity. Because unobservables or omitted variables are shared across severity levels, however, crash counts are multivariate in nature. This research uses full Bayes multivariate Poisson lognormal models to estimate the expected crash frequency for different levels of crash severity and then compares those estimates to independent or univariate Poisson lognormal estimates. The multivariate Poisson lognormal model fits better than the univariate model and improves the precision in crash-frequency estimates. The covariances and correlations among crash severities are high (correlations range from 0.47 to 0.97), with the highest values found between contiguous severity levels. Considering this correlation between severity levels improves the precision of the expected number of crashes. The multivariate estimates are used with cost data from the Pennsylvania Department of Transportation to develop the expected crash cost (and excess expected cost) per segment, which is then used to rank sites for safety improvements. The multivariate-based top-ranked segments are found to have consistently higher costs and excess costs than the univariate estimates, which is due to higher multivariate estimates of fatalities and major injuries (due to the random effects parameter). These higher estimated frequencies, in turn, produce different rankings for the multivariate and independent models. The finding of a high correlation between contiguous severity levels is consistent with some of the literature, but additional tests of multivariate models are recommended. The improved precision has important implications for the identification of sites with promise (SWiPs), because one formulation includes the standard deviation of crash frequencies for similar sites as part of the assessment of SWiPs.
TL;DR: In this article, the feasibility of using 100% RAP HMA as a base course with warm-mix asphalt (WMA) additives (Sasobit H8 or Advera zeolite) at a lower temperature (125°C) was investigated.
Abstract: The soaring cost of liquid asphalt binder and anticipated stricter environmental regulations have driven highway agencies to maximize the amount of reclaimed asphalt pavement (RAP) used for pavement construction. However, because of already aged and stiffened asphalt binder in RAP, the use of high percentages of RAP in hot-mix asphalt (HMA) presents many challenges. Problems with workability and compactability during construction need to be resolved first. This study investigated the feasibility of using 100% RAP HMA as a base course with warm-mix asphalt (WMA) additives (Sasobit H8 or Advera zeolite) at a lower temperature (125°C). Mix samples (control set with 100% RAP; a set with 100% RAP plus Sasobit H8 at 1.5%, 2.0%, and 5.0%; and a set with 100% RAP plus Advera zeolite at 0.3%, 0.5%, and 0.7%) were compacted with 50 gyrations. Their workability, bulk specific gravity, indirect tensile strength at 0°C, and moduli at 0°C, 26.7°C, and 50°C were determined. The effects of different amounts of WMA additi...
TL;DR: In this article, a laboratory investigation was conducted of moisture damage in WMA mixtures containing moist aggregates, and indirect tensile strength (ITS) and deformation and toughness tests were performed to determine the mixtures' moisture susceptibilities.
Abstract: In recent years, rising energy prices, global warming, and more stringent environmental regulations have generated interest in warm-mix asphalt (WMA) technologies as a means to decrease energy consumption and emissions associated with conventional hot-mix asphalt. In this study, a laboratory investigation was conducted of moisture damage in WMA mixtures containing moist aggregates. Indirect tensile strength (ITS), tensile strength ratio, deformation, and toughness tests were performed to determine the mixtures' moisture susceptibilities. The experimental design included two percentages of moisture content (0% and ~0.5% by weight of the dry mass of the aggregate), two WMA additives (Asphamin and Sasobit), and three aggregate sources. In this study 15 mix designs were performed, and 180 specimens were tested. Test results indicated that, as expected, dry ITS values were affected by aggregate moisture and hydrated lime contents, whereas a WMA additive did not significantly alter the dry ITS and toughness val...
TL;DR: In this paper, the authors analyzed 12 months of automated hourly pedestrian counts in downtown Montpelier, Vermont (population 8,035), along with weather data (temperature, relative humidity, precipitation, and wind) to determine the factors affecting count variability.
Abstract: Twelve months of automated hourly pedestrian counts in downtown Montpelier, Vermont (population 8,035), were analyzed along with weather data (temperature, relative humidity, precipitation, and wind) to determine the factors affecting count variability. This study is unique in that a large amount of data in a single location was collected in a locale with an extreme range of weather conditions. Results indicate consistent patterns in relative volumes by hour of the day and month of the year that show that good adjustment factors can be developed to use with time-limited counts to estimate usage and pedestrian exposure to accidents. Predictive relationships were found between weather variables, season, and pedestrian volumes (30% of the variation is accounted for). Consistent hourly patterns within a day and the consistency of day type (weekday or Saturday versus holiday or Sunday) suggest that correction factors and forecasting methods are feasible for pedestrian traffic volumes. The results indicate that weather such as cold temperatures or precipitation consistently reduces aggregate levels of walking by only a moderate amount (less than 20%). Precipitation and season are found to affect pedestrian levels even when time of day and day of week are controlled, but other, larger, unmeasured factors are at play.
TL;DR: In this paper, the authors proposed a framework of a model-based hot spot identification method by applying full-Bayes (FB) technique, which can seamlessly integrate prior information and all available data into posterior distributions on which various ranking criteria could be based.
Abstract: This study proposes a framework of a model-based hot spot identification method by applying full Bayes (FB) technique. In comparison with the state-of-the-art approach [i.e., empirical Bayes method (EB)], the advantage of the FB method is the capability to seamlessly integrate prior information and all available data into posterior distributions on which various ranking criteria could be based. With intersection crash data collected in Singapore, an empirical analysis was conducted to evaluate the following six approaches for hot spot identification: (a) naive ranking using raw crash data, (b) standard EB ranking, (c) FB ranking using a Poisson-gamma model, (d) FB ranking using a Poisson-lognormal model, (e) FB ranking using a hierarchical Poisson model, and (f) FB ranking using a hierarchical Poisson (AR-1) model. The results show that (a) when using the expected crash rate-related decision parameters, all model-based approaches perform significantly better in safety ranking than does the naive ranking method, and (b) the FB approach using hierarchical models significantly outperforms the standard EB approach in correctly identifying hazardous sites.
TL;DR: In this paper, the factors influencing the decision to bicycle are explored and unraveled to inform the development of appropriate and effective strategies to increase bicycling and promote the health of individuals and of the environment.
Abstract: The factors influencing the decision to bicycle are explored and unraveled to inform the development of appropriate and effective strategies to increase bicycling and promote the health of individuals and of the environment. The data used in the analysis were drawn from a survey of Texas bicyclists, and the study includes a comprehensive explanatory analysis of bicyclists and their bicycling habits. Various econometric models are used to evaluate the determinants of bicyclists' perception for safety and quality issues and the frequency of bicycling for commute and noncommute purposes. The results of the study indicate that the perceptions of the quality of bicycle facilities and safety from traffic crashes show significant variation depending on bicyclists' demographic and work characteristics and bicycle amenities and facilities on the commute route and at the workplace. Bicyclist demographics (gender, age, education level, commute distance), household demographics (number of automobiles, number of bicycles, number of children), residential location and season, bicycle amenities at work (bicycle racks, showers), bicyclist perceptions of the overall quality of bicycle facilities, and bicycle-use characteristics affect commute and noncommute bicycling frequency. These study results can assist in the development of informed policies to increase commute and noncommute bicycling, and the results highlight the ongoing need for detailed surveys to understand bicycling behavior.
TL;DR: A statistical model was developed to reveal and quantify the main factors defining transport-related consequences of link failures, including congestion effects on a networkwide scale and demonstrates that detours are by far the predominant demand reaction.
Abstract: This paper presents a methodology that incorporates vulnerability to natural hazards into current infrastructure management systems. The paper is mainly concerned with presenting the methodology applied to assess the transport-related consequences of link failures, including congestion effects on a networkwide scale. Four possible demand shifts caused by single link failures can be expected: detours, shifts in mode choice, shifts in destination choice, and trip–activity suppression. The paper demonstrates that detours are by far the predominant demand reaction. Hence, the quantification of detour-based principal consequences is the main focus. The main challenge was to overcome the calculation time intensity of this equilibrium-based approach. Since demand shift effects were assumed to be spatially restricted around the failed link, subnetworks were used, that is, limited sections of the complete network that were cut out, including their internal and transit demands. The resulting failures turned out to be consistent with those that involved the full network, even for links with long path distances or long detours. On the basis of computed consequences of link failures and on link parameters, a statistical model was developed to reveal and quantify the main factors defining transport-related consequences. Furthermore, the findings highlight potential gains, including rail networks, mode shifts, and destination choice shifts in network vulnerability assessments.
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TL;DR: In this paper, the authors reviewed what is known about the evolution of speed over time and space, and how it affects road safety, and discussed how to predict the consequences of speed changes.
Abstract: The speed at which people elect to travel is affected by vehicle and road design; by limits to speed and enforcement of those limits; by traffic control, signs, and markings; and so forth. The speed at which people travel, in turn, affects road safety. In this context two questions arise: (a) How is the evolution of speed over time and space affected by what drivers do? (b) How does speed affect safety? This paper reviews what is known, notes the gaps in knowledge, and describes where opinions differ and why. Unfortunately, despite decades of speed measurement and monitoring, the evolution of speed over time is poorly documented, and the understanding of what drives the evolution is largely missing. It is known that speeds evolve over time, but not why; it is known that there is some spillover of the change from one road to another, but its size or extent cannot be predicted. This is a neglected field of inquiry. More is known in answer to Question b. There can be no reasonable doubt that if speed increases while other conditions (vehicles, roads, medical services) remain unchanged, the accidents that occur will tend to be more severe. However, the prevalent and strongly held belief that the greater the speed, the higher is the probability that accidents will occur is, at present, not well supported by research. Even so, given a change in mean speed, one can predict the consequences in injuries and fatalities and this paper discusses how to do so.
TL;DR: In this article, two types of spatial modeling techniques, the Gaussian conditional autoregressive (CAR) and the multiple membership (MM) models, were compared with the traditional Poisson-lognormal model.
Abstract: This paper investigates the inclusion of spatial effects in accident prediction models. Two types of spatial modeling techniques—the Gaussian conditional autoregressive (CAR) and the multiple membership (MM) models—were compared with the traditional Poisson-lognormal model. A variation of the MM model (extended MM or EMM) was also investigated to study the effect of clustering segments within the same corridor on spatial correlation. Full Bayes estimation was used by means of the Markov chain Monte Carlo methodology to estimate the parameters. The study made use of 281 urban road segments in Vancouver, British Columbia, Canada. Various traffic and geometric variables were included in the accident prediction models. The models were compared in terms of their goodness of fit and inference. For the data set under consideration, the results showed that annual average daily traffic, business land use, the number of lanes between signals, and the density of unsignalized intersections have significant positive i...
TL;DR: In this paper, the authors examine the relationship between the availability of transportation infrastructure and services and the pattern of house prices in an urban area and assess whether public investment in transportation can modify residential property values.
Abstract: The aim of this paper is to examine the relationship between the availability of transportation infrastructure and services and the pattern of house prices in an urban area and to assess whether public investment in transportation can modify residential property values. This study was developed for the Lisbon, Portugal, metropolitan area (LMA) as part of a broader study that intends to develop new value-capture financing schemes for public transportation in the LMA. The paper focuses on three central municipalities in Portugal (Amadora, Lisbon, and Odivelas), where these effects could be more easily measured because of the existence of a significant variability of public transportation services. The paper tries to determine, with different spatial hedonic pricing models, the extent to which access to transportation infrastructure currently is capitalized into house prices and isolates the influence of three different transportation infrastructures: metro, rail, and road. The results suggest that the proxi...
TL;DR: This paper presents a case study for the Metropolitan Transit Authority's New York City Transit, a transit system in which a rider swipes a fare card only to enter a station or board a bus, the first work to include trips by all transit modes in a system that records the transaction only on rider entry.
Abstract: Many large transit systems use automatic fare collection (AFC) systems. Most AFC systems were designed solely for revenue management, but they contain a wealth of customer use data that can be mined to create inputs to operations planning and demand forecasting models for transportation planning. More detailed information than could ever be collected by any travel survey is potentially available if it is assumed that the transactional data can be processed to produce the desired information. Previous work in this field focused primarily on rail transit, since boardings at fixed stations are easier to locate than boardings of buses, which move around. This paper presents a case study for the Metropolitan Transit Authority's New York City Transit, a transit system in which a rider swipes a fare card only to enter a station or board a bus. This is the first work to include trips by all transit modes in a system that records the transaction only on rider entry, which is significantly more challenging because ...
TL;DR: In this article, the authors assess the impacts of failed first-time home deliveries on additional carrier journeys (repeat deliveries) and customer trips (to retrieve goods from carrier depots) and are assessed in this paper.
Abstract: The impacts of failed first-time home deliveries on additional carrier journeys (repeat deliveries) and customer trips (to retrieve goods from carrier depots) are of increasing concern to e-retailers and are assessed in this paper. The attended collection and delivery point (CDP) concept is one solution to first-time delivery failures, using a variety of outlets (e.g., convenience stores, petrol stations, post offices) as alternative addresses to receive deliveries. By using a database of households from across West Sussex in the United Kingdom, this paper confirms that certain benefits might accrue from using networks of Local Collect post offices, supermarkets, and railway stations as CDPs, compared with the traditional delivery method in which the carrier may make several redelivery attempts to the home with the customer making a personal trip to the carrier's depot in the event that these attempts also fail. A network of CDPs across West Sussex would function most effectively (in reducing the overall ...
TL;DR: In this article, the authors identify for transportation planners five key implications of extending cap-and-trade for greenhouse gas emissions to the transportation sector, as envisaged in legislative and regulatory proposals in the U.S. Congress and in the western states and Canadian provinces.
Abstract: This paper identifies for transportation planners five key implications of extending cap-and-trade for greenhouse gas emissions to the transportation sector, as envisaged in legislative and regulatory proposals in the U.S. Congress and in the western states and Canadian provinces. First, cap-and-trade would increase gasoline prices as refiners and fuel importers pass on the cost of carbon allowances; a $30 per metric ton price of carbon allowances equates to 27 cents per gallon of gasoline. Second, transit, smart growth, and other emission reduction projects might be eligible for billions of dollars in revenue from carbon allowance auctions. Third, as emissions would be constrained at the level of the cap, transportation projects would be unlikely to have any impact on aggregate emissions. Any environmental benefit of a project (reduced emissions) would be converted into an economic benefit (reduced carbon allowance prices and thus reduced compliance costs in other sectors). Fourth, the converse of this argument suggests a weakening of the potential to use the environmental review process to mitigate emissions from development projects. There may be an economic impact (higher carbon allowance prices), but not an environmental impact (emissions would be constrained at the level of the cap). Finally, extending cap-and-trade to the transportation sector would eliminate the potential for revenue from the sale of offsets, as this would double count emission reductions.
TL;DR: In this article, an evaluation of the economic, environmental, and mixture performance factors to assess the sustainability of WMA in North America is presented, and the benefits, risks, in...
Abstract: During the past 3 years, warm-mix asphalt (WMA) technologies from European countries have entered the North American market. European experiences with WMA technologies have indicated that a significant reduction in mixture temperature, mixture viscosity, energy consumption, and environmental emissions during asphalt mix production and placement can be achieved in comparison with traditional hot-mix asphalt (HMA). On the basis of North American experiences with these technologies to date, transportation agencies and HMA producers are unlikely to adopt WMA technologies solely for the reduction in manufacturing energy costs and environmental emissions, because these benefits do not cover the associated increase in investment and additive costs of WMA over HMA, even in the most expensive North American energy markets. This paper presents an evaluation of the economic, environmental, and mixture performance factors to assess the sustainability of WMA in North America. The paper examines the benefits, risks, in...
TL;DR: In this paper, an incompatible binder and a compatible base asphalt binder were selected and modified with various amounts of styrene-butadiene-styrene (SBS) in different proportions.
Abstract: The rheological properties of asphalt binders modified by styrene-butadiene-styrene (SBS) depend on formulation variables. The most sensitive of them may be listed as polymer amount, cross-linking agent amount (percentage), and other additives such as polyphosphoric acid (PPA). The dispersion of SBS in an asphalt binder depends on the time and temperature of blending and the base asphalt binder compatibility. In this study an incompatible binder and a compatible base asphalt binder were selected and modified with various amounts of SBS. Elemental sulfur was used as a cross-linking agent in different proportions. Other additives, such as PPA at 0.5% concentration, were also used. High shear blends of SBS-modified asphalt binders were made in the laboratory by varying blending time until an optimum dispersion of polymer was obtained. The dispersion of the polymer was studied with a fluorescence microscope. A multiple stress creep and recovery (MSCR) test was used to study creep and recovery behavior of thes...