Showing papers in "Transportation Research Record in 1997"
TL;DR: In this paper, the relative significance and influence of a variety of measures of urban form on household vehicle kilometers traveled, automobile ownership, and mode choice were investigated for the 1990 San Francisco Bay Area travel surveys, and the land use data were largely constructed from hectare-level descriptions provided by the Association of Bay Area Governments.
Abstract: The relative significance and influence of a variety of measures of urban form on household vehicle kilometers traveled, automobile ownership, and mode choice were investigated. The travel data came from the 1990 San Francisco Bay Area travel surveys, and the land use data were largely constructed from hectare-level descriptions provided by the Association of Bay Area Governments. After demographic characteristics were controlled for, the measures of accessibility, land use mixing, and land use balance—computed for trip-makers' home neighborhoods and at trip ends—proved to be highly statistically significant and influential in their impact on all measures of travel behavior. In many cases, balance, mix, and accessibility were found to be more relevant (as measured by elasticities) than several household and traveler characteristics that often form a basis for travel behavior prediction. In contrast, under all but the vehicle ownership models, the impact of density was negligible after accessibility was co...
539 citations
TL;DR: ALINEA, a local feedback ramp-metering strategy, has had multiple field applications, and more applications are planned in several European countries.
Abstract: Asservissement Lineaire d'Entree Autoroutiere (ALINEA), a local feedback ramp-metering strategy, has had multiple field applications, and more applications are planned in several European countries. The main features of ALINEA are presented and the field results achieved to date at both single and multiple ramps of the Boulevard Peripherique in Paris and at the A10 West motorway in Amsterdam are summarized. The reported results indicate easy application, flexibility, and high efficiency of ALINEA. Planned implementations are outlined.
389 citations
TL;DR: In this paper, the authors developed a bicycle-quality model for applications in U.S. metropolitan areas based on real-time perceptions from bicyclists traveling in actual urban traffic and roadway conditions.
Abstract: The primary focus of this study by Sprinkle Consulting Engineers, Inc. is to develop a bicycle-quality, or level-of-service, model for applications in U.S. metropolitan areas. Although there are several model forms being used throughout the United States that attempt to quantify road suitability or the quality of service afforded bicyclists traveling the street and roadway networks of urbanized areas, to date there have been no statistically calibrated models published. The statistically calibrated level-of-service model described here is based on real-time perceptions from bicyclists traveling in actual urban traffic and roadway conditions. The study's participants represented a cross section of age, gender, experience level, and geographic origin of the population of cyclists that use the metropolitan road networks in the United States. The test course is representative of the collector and arterial street systems of North American urban areas. Although further hypothesis testing is being conducted and ...
328 citations
TL;DR: A cross-nested model that is derived from the generalized extreme value class and that can be thought of as a generalization of the nested logit model is proposed, which takes into account the cross similarities between different pure and combined modes.
Abstract: Currently, modal split modeling is done mainly by means of disaggregated mode choice models. The almost absolute dominance of multinomial and nested logit models over other mode choice models among applied transportation modelers is attributable to their theoretical soundness, to their simple and understandable analytical structure, and to the calibration procedures that have been developed. Typical urban transport systems, however, are characterized by a variety of modes including private (automobile), public transit (bus, suburban rail, light rail, and subway), and various combinations of these. Analysis reveals that the nested logit model based on the assumption of groupwise similarities among modes is not a suitable modeling tool in such situations. A cross-nested model that is derived from the generalized extreme value class and that can be thought of as a generalization of the nested logit model is proposed. The model takes into account the cross similarities between different pure and combined mode...
273 citations
TL;DR: In this paper, the authors examined whether high or low incidence of pedestrian travel in mixed-use, medium-density environments is due to site design characteristics, and specifically to presence of direct, continuous, and safe pedestrian systems.
Abstract: Whether high or low incidence of pedestrian travel in mixed-use, medium-density environments is due to site design characteristics, and specifically to presence of direct, continuous, and safe pedestrian systems, is examined. Twelve neighborhood centers or sites in the Puget Sound area of Washington were selected by matching gross residential density, median income, automobile ownership, and intensity and type of neighborhood commercial development. Pedestrians and bicyclists were recorded that traveled into the commercial area. A clear break emerges between urban and suburban sites. The average urban pedestrian volume is 37.7 pedestrians per hour per 1,000 residents, which is 3 times higher than the 12.5 pedestrians per hour per 1,000 residents in suburban sites. These results strongly support the hypothesis that, when holding other variables constant, the urban versus suburban difference in route directness and completeness of pedestrian facilities (namely, block size and sidewalk length) affects pedestrian volumes. The research also questions the common belief that people do not walk in the suburbs. Given appropriate land use conditions, pedestrian facility improvement programs in suburban areas can support pedestrian travel and have a significant influence on mode choice.
255 citations
TL;DR: In this paper, a cross-sectional analysis of bicycle pathways in 18 U.S. cities was conducted to investigate the relationship between bicycle pathway supply and commuting by bicycle, and a positive association was found between bicycle pathways per 100,000 residents and the percentage of commuters using bicycles.
Abstract: Conventional wisdom suggests that if bicycle pathways are provided, people will use them. This assertion is based on a combination of anecdotes, a few case studies, and mostly wishful thinking. Until now, there have been no cross-sectional studies of the association between bicycle pathway supply and commuting by bicycle that control for a variety of factors. Cross-sectional analysis, controlling for a variety of extraneous factors, can help to attribute differences in bicycle commuting to the overall supply of pathways. Cross-sectional data are applied here to 18 U.S. cities to help fill this gap in research. After considering such factors as weather, terrain, and number of college students, a positive association was found between miles of bicycle pathways per 100,000 residents and the percentage of commuters using bicycles. It is speculated that one problem with shifting the mode of commuting away from automobiles may simply be an inadequate supply of bicycle facilities. Although this work is the first of its kind, more systematic research is needed to confirm its findings.
251 citations
TL;DR: In this article, the general relationship between hourly accident rates and hourly traffic volume/capacity (vie) ratios was examined and a 26 km (16 mi) segment of Interstate I-94 in the Detroit area was selected as the study segment.
Abstract: The general relationships between hourly accident rates and hourly traffic volume/capacity (vie) ratios were examined. A 26 km (16 mi) segment of Interstate I-94 in the Detroit area was selected as the study segment. The v/c ratios were calculated from average hourly traffic volume counts collected in 1993 and 1994 from three permanent count stations. Accident rates were derived from hourly distributed number of accidents in the same 2 years. The correlation between v/c values and accident rates follows a general U-shaped pattern. The study of all observed accidents combined indicates that accident rates are highest in the very low hourly v/c range, decrease rapidly with increasing v/c ratio, and then gradually increase as the v/c ratio continues to increase. U-shaped models also explain the relationship between v/c and accident rates for weekdays and weekend days, multivehicle, rear-end, and property-damage-only accidents. On the other hand, single-vehicle, fixed-object, and turnover accidents, and accid...
211 citations
TL;DR: In this paper, a geographic information system (GIS) network data base is used to determine the characteristics of 397 routes used by commuter cyclists in Guelph, Ontario, Canada, and to compare them with the shortest-path routes between each origin and destination.
Abstract: A geographic information system (GIS) network data base is used to determine the characteristics of 397 routes used by commuter cyclists in Guelph, Ontario, Canada, and to compare them with the shortest-path routes between each origin and destination. The analysis of route data provides useful insight for understanding factors affecting travel behavior and in this case provides quantitative support for many existing assumptions regarding commuter cyclist behavior. Most commuters divert very little from their minimum path (0.4 km on average) and are found to use major road routes. The cyclists tend to avoid grades, grade-separated railway crossings, and high-activity areas, but not road (as opposed to pedestrian) bridges. Cyclists use traffic signals especially for crossing major roadways and turning. The high-quality direct off-road paths are used only infrequently by the commuter cyclists and the lower quality ones even less. The results of this analysis suggest that efforts to accommodate current commut...
207 citations
TL;DR: In this article, a travel survey of individual riders was used to develop a disaggregate discrete choice logit model of walk access to BART stations, and linear regression analysis of aggregate station area characteristics was developed; density, the number of parking spaces at the station, and income and education of the residents were identified as key factors in the decision to walk.
Abstract: Walking links practically every trip taken, yet it has not been maximized as a primary mode of transportation, and the characteristics of walk trips are little understood. The Bay Area Rapid Transit (BART) system has been used for primary analysis of characteristics of pedestrian access to transit. A travel survey of individual riders was used to develop a disaggregate discrete choice logit model of walk access to BART stations. Characteristics with the highest probability of choosing walking over another mode are distance, availability of a car, and gender. Linear regression analysis of aggregate station area characteristics was developed; density, the number of parking spaces at the station, and income and education of the residents were identified as key factors in the decision to walk. When the logit and regression models were combined into a single model, there was a clear shift toward individual characteristics over aggregate station area characteristics that determines access-mode choice. Among phy...
167 citations
TL;DR: In this article, four groups of capacity estimation methods, namely, headway distribution, bimodal distribution, selected maxima, direct probability and product limit, are compared.
Abstract: Capacity is a central concept in roadway design and traffic control. Estimation of empirical capacity values in practical circumstances is not a trivial problem; it is very difficult to define capacity in an unambiguous manner. Empirical capacity estimation for uninterrupted roadway sections has been studied. Headways, traffic volumes, speed, and density are traffic data types used to identify four groups of capacity estimation methods. Aspects such as data requirement, location choice, and observation period were investigated for each method. The principles of the different methods and the mathematical derivation of roadway capacity are studied and discussed. Among the methods studied are the headway distribution approaches, the bimodal distribution method, the selected maxima, and the direct probability method. Of the methods based on traffic volume counts, the product limit method is recommended for practical application because of sound underlying theory. An example of the application of this promisin...
162 citations
TL;DR: In this article, the effect of automatic speed enforcement on the number of injury accidents varied according to the level of conformance with official warrants for its use, which referred to accident rate and accident density.
Abstract: Automatic speed enforcement by means of photo radar was introduced in Norway in 1988. The results of a before-and-after study of the effects of automatic speed enforcement on accidents are reported in this paper. The study controlled for general trends in the number of accidents and regression to the mean. A statistically significant reduction of 20 percent in the number of injury accidents was found. The number of property-damage-only accidents was reduced by 12 percent. This change was not statistically significant at the 5 percent level. The effect of automatic speed enforcement on the number of injury accidents varied according to the level of conformance with official warrants for its use. The warrants refer to accident rate (accidents per vehicle kilometer) and accident density (accidents per kilometer of road). A decline of 26 percent in injury accidents was found on road sections conforming with both warrants. On road sections not conforming with any of the warrants, injury accidents declined by 5...
TL;DR: In this article, a hedonic price function is used to estimate property values and the effect of proximity to rail transit stations and the benefits of living near high-quality rail transit station provides an array of benefits.
Abstract: For many Americans, living near high-quality rail transit stations provides an array of benefits. The benefits arise from lower transportation expenses, changing development patterns, and other nonuse factors. Automobile-centered development patterns increase congestion, sprawl, and pollution. The benefits of transit-oriented neighborhoods are explored. A hedonic price function is used to estimate property values and the effect of proximity to rail transit stations. Geographical information system databases were used to calculate actual walking distances to transit, providing a much more accurate measure of the “proximity” variable than the usual measure of straight-line distance. The results indicate that proximity to rail transit stations can be a significant source of benefit to residents within walking distance. Whereas light rail transit stations in Portland, Oregon, indicate minimal effects, the magnitude of the benefits for the Bay Area Rapid Transit and New York City Metropolitan Transportation Au...
TL;DR: In this article, the authors describe the development and application of transit accessibility measures by geographic information system technology, which allows transit planners to focus on access to transit routes and bus stops at the neighborhood level and draws attention to the significance of the walk access mode to transit.
Abstract: The development and application of transit accessibility measures by geographic information system technology are described. The approach allows transit planners to focus on access to transit routes and bus stops at the neighborhood level and draws attention to the significance of the walk access mode to transit. Then land use, population, and employment characteristics are incorporated into the evaluation of transit service. A case study example of a "what-if" scenario for evaluation of transit service alternatives is discussed. Conclusions are offered about the use and further development of the approach for transit planners.
TL;DR: In this article, a pedestrian survey conducted in two pairs of Austin, Texas, neighborhoods that possess either pedestrian-oriented or automobile-oriented transportation system, land use, and design characteristics but similar density, housing, and sociodemographic characteristics are reported.
Abstract: Results of a pedestrian survey conducted in two pairs of Austin, Texas, neighborhoods that possess either pedestrian-oriented or automobile-oriented transportation system, land use, and design characteristics but similar density, housing, and sociodemographic characteristics are reported. Survey results identify the influence of contrasting neighborhood forms on structural characteristics of walk-activity patterns and attitudes as mediated by personal characteristics. Walk-activity patterns significantly vary between neighborhoods with different accessibility characteristics. In the physically accessible neighborhoods, walks are predominantly short and frequent utilitarian trips that involve more secondary activities. Activity in the less accessible neighborhoods is characterized by longer, less frequent recreational walks that involve fewer secondary activities. Results support the conclusion that neighborhood transportation, land use, and design characteristics influence walk distance, duration, purpose...
TL;DR: In this paper, a comprehensive modal emission model for light-duty cars and trucks is developed, based on a simple parameterized physical approach and consists of six modules that predict engine power, engine speed, air/fuel ratio, fuel use, engine-out emissions, and catalyst pass fraction.
Abstract: A comprehensive modal emission model for light-duty cars and trucks is being developed. More than 300 real-world vehicles are being recruited for in-house dynamometer testing under as-is conditions to provide the foundation for the model. The model is designed to predict second-by-second tailpipe emissions under a variety of driving conditions. The vehicles can be modeled as individual vehicles with properly functioning, deteriorated, or malfunctioning emission control conditions, or as composite vehicles representing different vehicle technology categories. The model is based on a simple parameterized physical approach and consists of six modules that predict engine power, engine speed, air/fuel ratio, fuel use, engine-out emissions, and catalyst pass fraction. When developing the model, four important vehicle operating conditions are considered: cold and warm starts; normal, stoichiometric operation; high-power enrichment; and lean-burn operation. The model concept and the expected input/output requirem...
TL;DR: In this paper, a modified form of nested logit model was developed and estimated using disaggregate revealed preference observations collected in Calgary, Alberta, Canada, where three categories of choice were treated as a joint choice made by the household, allowing for differing numbers of workers in different households.
Abstract: Household behavior in the selection of home location and the selection of workplace locations and commuting modes for employed members involves trade-offs among the attributes of the available alternatives for the different household members. A modified form of nested logit model representing this behavior has been developed and estimated using disaggregate revealed preference observations collected in Calgary, Alberta, Canada. Three categories of choice—choice of home location for the household, choice of workplace location for each worker in the household, and choice of mode for the trip to work for each worker in the household—are treated as a joint choice made by the household, allowing for differing numbers of workers in different households. A nesting structure that takes into account the greater similarity among mode alternatives is combined with a system for weighting, by age and gender, the contributions of different individual workers' utilities to the total household utility. This leads to a ne...
TL;DR: In this paper, a new algorithm for queue management and coordination of traffic signals along oversaturated arterials is presented, where the main idea is to manage queue formation and dissipation on system links so that traffic flow is maximized by efficiently using all green time, preventing formation of de facto red, accounting for the non-steady state conditions, and providing time-dependent control measures.
Abstract: The formulation and solution of a new algorithm for queue management and coordination of traffic signals along oversaturated arterials are presented. Existing traffic-control and signal-coordination algorithms deal only with undersaturated steady-state traffic flow conditions. No practical algorithms are readily available for oversaturated flow conditions. The main idea of the procedure is to manage queue formation and dissipation on system links so that traffic flow is maximized by efficiently using all green time, preventing formation of de facto red, accounting for the non-steady-state conditions, and providing time-dependent control measures. The problem is formulated as a throughput maximization problem subject to state and control variables. The solution is then obtained using genetic algorithms. The results show that the control procedure can produce dynamic and responsive control so that traffic progression is attained and all undesirable conditions such as queue spill-back and de facto red are avoided.
TL;DR: The results of this survey should be of interest to policy makers, businesses, and advocates interested in promoting the use of the bicycle for transportation purposes.
Abstract: Although interest exists in promoting bicycle commuting to help meet air quality and commuter-trip reduction goals, there are virtually no data on bicycle commuters. A comprehensive survey, distributed over the Internet and by mail, of such commuters has been conducted, with 2,374 responses received from all regions of the United States and Canada. Information was gathered in seven categories: about your commuting; about the facilities you use; about your bike; about your motivation; about safety/accidents; about your health; and about you and your household. Comments were also collected. Although the average bicycle commuter is a 39-year-old male professional with a household income in excess of $45,000 per year who rides 10.6 months per year, nearly one in five respondents was female. Average annual bicycle-commuting distance was 3100 km, although these same cyclists rode an average of 5500 km for all trip purposes. Just under 10 percent reported having an accident in the previous 12 months. A relative ...
TL;DR: In this article, the authors evaluated the impact of traffic flow, truck percentage, truck type (i.e., length and weight/horsepower ratio), grade, and length of grade on passenger car equivalents (PCEs) for different truck types for the full range of traffic conditions on freeways, two-lane highways and arterials.
Abstract: Passenger car equivalents (PCEs) have been used extensively in the Highway Capacity Manual to establish the impact of trucks, buses, and recreational vehicles on traffic operations. PCEs are currently being used for studying freeways, multilane highways, and two-lane highways. A heavy-vehicle factor is directly given for the impact of heavy vehicles at signalized intersections (and indirectly along arterials). These PCE values are typically based on a limited number of simulations and on older simulation models. In addition, the impact of variables such as traffic flow, truck percentage, truck type (i.e., length and weight/horsepower ratio), grade, and length of grade on PCEs has not been evaluated in depth for all facility types. The methodology for developing PCEs for different truck types for the full range of traffic conditions on freeways, two-lane highways, and arterials is described. Given the scope of this research and the variability of traffic conditions to be examined, simulation was selected a...
TL;DR: In this article, an empirical assessment of the interaction between the land use-transportation system and travel behavior is presented, and a methodology for identifying a range of land usetransportation systems by a clustering technique with network and land use inputs is developed.
Abstract: An empirical assessment of the interaction between the land use—transportation system and travel behavior is presented. A methodology for identifying a range of land use—transportation systems by a clustering technique with network and land use inputs was developed. Twenty neighborhoods from Orange County, California, were considered in this process. Three groups, or themes, were found to best represent the neighborhoods in the sample area: one each associated with the conventional definition of traditional and neotraditional neighborhood design (TND) and planned unit development (PUD) neighborhoods and one representing neighborhoods that blend characteristics of TND and PUD. Conventional measures of individual travel behavior were compared with an analysis of variance between the themes to identify significant differences, controlling for socioeconomic characteristics. Research results include the development of (a) a systematic methodology to identify a more explicit land use—transportation dimension, (...
TL;DR: In this article, a simple laboratory test for evaluating unstabilized granular base material is introduced, which consists of monitoring the capillary rise of moisture within a 300mm-high cylinder of compacted aggregate.
Abstract: A simple laboratory test for evaluating unstabilized granular base material is introduced. The test consists of monitoring the capillary rise of moisture within a 300-mm-high cylinder of compacted aggregate. The moisture conditions at the aggregate surface are monitored with a dielectric probe. A graph of surface dielectric versus time is used as the basis for performance classification. The poorest-performing materials are those that rapidly reach saturation and exhibit high surface dielectric values. The dielectric is a measure of the “free” or unbound water within the aggregate sample. It is not a simple measure of the moisture content of the material but an assessment of the state of bonding of the water within the fine aggregates. It is this unbound water that is thought to be directly related to the strength of the material and to its ability to withstand repeated freeze-thaw cycling. This test was developed by the Finnish National Road Administration and successfully used to investigate a major fle...
TL;DR: In this paper, the authors explored the relationship between demographic attributes and spatial clustering of individuals making a weekday bicycle journey-to-work commute and their commuting travel time and found that cyclists traveling primarily on separated paths tend to make significantly longer trips.
Abstract: The relationship between the demographic attributes and spatial clustering of individuals making a weekday bicycle journey-to-work commute and their commuting travel time is explored. The study uses data from a 1993 bicycle-intercept survey distributed in Seattle, Washington, in which individual bicycle-travel behavior characteristics were collected. The data include socioeconomic information, such as age, gender and income. The results indicate that these three factors may play unexpected roles in the length of bicycle commuting travel times for the journey-to-work trips. This study also suggests that separated bicycle paths play an integral part in the overall bicycle transportation network. Statistical analysis also indicated that cyclists traveling primarily on separated paths tend to make significantly longer trips.
TL;DR: In this article, the authors examined short-term and sustained effects on red-light compliance and potential vehicle conflicts as a result of an increase in change intervals to values associated with the Institute of Traffic Engineers (ITE) proposed recommended practice for determining vehicle change intervals.
Abstract: Motor vehicle crashes at traffic signals are a major source of injuries and property damage, especially in urban areas. Many crashes result from vehicles entering the intersection after the onset of a red light, a traffic violation that may be affected by the duration of the change interval (the yellow and all-red periods of the traffic signal). The purpose of this study was to examine short-term and sustained effects on red-light compliance and potential vehicle conflicts as a result of an increase in change intervals to values associated with the Institute of Traffic Engineers (ITE) proposed recommended practice for determining vehicle change intervals. Data were collected during an experiment in an urban location involving changes in signal timing at some 10 intersections. Observations included the proportion of signal cycles with vehicles entering on a red light and the proportion of vehicles exiting the intersection after the onset of a conflicting green signal. Results indicate that change intervals...
TL;DR: In this paper, a cross-anisotropic model is proposed to predict the performance of granular bases in flexible pavements, which can account for the dilative behavior observed under the wheel load and the effects of compaction-induced residual stresses.
Abstract: A new cross-anisotropic model is proposed to predict the performance of granular bases in flexible pavements. A cross-anisotropic representation has different material properties (i.e., elastic modulus and Poisson's ratio) assigned in the horizontal and vertical directions. Repeated-load triaxial tests with vertical and lateral deformation measurements can be used to establish these anisotropic properties. Simple stress-dependent granular material models, obtained from analysis of the laboratory test data, are used in a nonlinear finite element program, named GT-PAVE, to predict pavement responses. The horizontal and shear stiffnesses are typically found to be less than the vertical. The nonlinear anisotropic approach is shown to account effectively for the dilative behavior observed under the wheel load and the effects of compaction-induced residual stresses. The main advantage of using a cross-anisotropic model in the base is the drastic reduction or elimination of significant tensile stresses generally predicted by isotropic linear elastic layered programs.
TL;DR: In this paper, a closed form solution for calculating the stresses in a pavement slab due to nonlinear gradients is introduced. But, the actual distributions of such gradients have been found to be highly nonlinear.
Abstract: Temperature and moisture gradients can lead to significant tensile stresses at the slab top and bottom. Current techniques for assessing the internal stresses due to such gradients are based on the assumption that temperature and moisture distributions through the slab thickness are linear. However, the actual distributions of such gradients have been found to be highly nonlinear. A new closed form solution technique for calculating the stresses in a pavement slab due to nonlinear gradients is introduced. The analysis is separated into two parts. In the first, an expression is presented for calculating the self-equilibrated stresses within a cross section due to internal restraint (i.e., satisfying equilibrium conditions and continuity of the strain field within the cross section). These stresses are independent of slab dimensions and boundary conditions. In the second, the stresses due to external restraint (i.e., self-weight and subgrade reaction) are calculated using an equivalent linear temperature gradient obtained from the first part and existing closed form solutions by Westergaard or Bradbury. The solution to this step includes slab length and boundary conditions. Total internal stresses due to nonlinear gradients are obtained by using the superposition principle. The methodology has been applied to field data from two studies in which the temperature profiles were recorded throughout a 24-hr period. Linear gradient solution methods cannot accurately predict the curling stresses in concrete pavements. This is especially pronounced during nighttime and early morning hours, during which nonlinear analysis predicts tensile stress in both the slab bottom and top before the application of any traffic loading.
TL;DR: In the course of describing the usefulness of this technique for estimating several measures, including the maximum length of a physical queue and the time when this maximum occurs, the difference between “delay” at a bottleneck and the “time spent in queue,” is clarified.
Abstract: A simple approach is described for modifying an input-output (or queue-ing) diagram to measure the time and distance spent by vehicles in a queue in a much simpler and self-serving manner than a time-space diagram. The graphic technique requires construction of a curve depicting the cumulative number of vehicles to have reached the back of the queue as a function of time, but, as indicated here, the technique can be easily automated with a spreadsheet. The technique is applied to the simple case of a constant departure rate from a bottleneck and to the slightly more general case of a bottleneck capacity that changes once, which is demonstrated to be applicable to the study of an undersaturated traffic signal. In the course of describing the usefulness of this technique for estimating several measures, including the maximum length of a physical queue and the time when this maximum occurs, the difference between “delay” at a bottleneck and the “time spent in queue,” which appears to have been confused in so...
TL;DR: In this paper, the authors examined the freeze-thaw durability of concrete with ground waste tire rubber and found that 10 and 15 percent rubber by weight of cement is more durable than other types of rubber.
Abstract: Used tires represent an increasingly serious environmental problem in the United States. This study examines the freeze-thaw durability of concrete with ground waste tire rubber. Various percentages of rubber, by weight of cement, were added to a control concrete mixture. To evaluate the freeze-thaw durability of these “rubcrete” mixtures, freeze-thaw tests in accordance with ASTM C666 Procedure A and microscopic analyses in accordance with ASTM C457 Procedure B, were conducted. Results show that the rubcrete mixtures with 10 and 15 percent rubber by weight of cement are freeze-thaw durable. Results of the microscopic analysis indicate that properties such as air content and spacing factors are difficult to determine accurately because of the problems associated with polishing of the rubcrete specimens.
TL;DR: In this paper, a framework for a process that can be used to select the proper maintenance strategies for different distress types in asphalt pavements, depending on traffic level and environment, is discussed.
Abstract: Preventive maintenance techniques are considered useful in extending the life of a pavement if applied at the right time. Discussed here is a framework for a process that can be used to select the proper maintenance strategies for different distress types in asphalt pavements, depending on traffic level and environment. Maintenance treatments addressed include only crack seals, fog seals, slurry seals, microsurfacings, chip seals, thin asphalt concrete overlays, and other thin surface treatments. Types of distress considered include roughness, rutting, fatigue cracking, longitudinal cracking, raveling, weathering, and bleeding. Decision trees, based on the authors' experiences, are presented to illustrate the process in selecting appropriate maintenance treatments. A framework for evaluating the cost-effectiveness of the various maintenance treatments is presented. Existing methods for evaluating cost-effectiveness of maintenance are discussed together with their strengths and weaknesses. An example of cost-effectiveness for different maintenance treatments is also briefly presented.
TL;DR: In this paper, a discrete choice model is used to quantify transfer penalties and their effects on mode choice in different transfer contexts, and revealed and stated preference data from the New York-New Jersey commute corridors are used to estimate logit models of mode choice reflecting the impacts of modal transfers.
Abstract: Since the passage of the Intermodal Surface Transportation Efficiency Act of 1991 there has been an increasing interest in the planning and design of an intermodal passenger transportation system. It has long been recognized that modal transfer has a certain penalty associated with it. The recent surge in intermodal planning merits an in-depth examination and accurate measurement of the penalties associated with transfers between modes. Current planning procedures usually involve an ad hoc treatment of transfer penalties based on various assumptions of wait time and value of time. To better assess the disutility associated with modal transfers, discrete choice models are used to quantify transfer penalties and their effects on mode choice in different transfer contexts. Revealed and stated preference data from the New York-New Jersey commute corridors are used to estimate logit models of mode choice reflecting the impacts of modal transfers. The model results suggest that the penalty factor associated with transfer time should be higher than that traditionally used in travel demand models and that the value of the transfer penalty varies according to the type of modal transfer.
TL;DR: A sequential approach to generating synthetic daily individual activity-travel patterns was developed and results indicate that the predicted pattern of activity choices conforms with observed choices by time of day.
Abstract: Microsimulation approaches to travel demand forecasting are gaining increased attention because of their ability to replicate the multitude of factors underlying individual travel behavior. The implementation of microsimulation approaches usually entails the generation of synthetic households and their associated activity-travel patterns to achieve forecasts with desired levels of accuracy. A sequential approach to generating synthetic daily individual activity-travel patterns was developed. The sequential approach decomposes the entire daily activity-travel pattern into various components, namely, activity type, activity duration, activity location, work location, and mode choice and transition. The sequential modeling approach offers practicality, provides a sound behavioral basis, and accurately represents an individual's activity-travel patterns. In the proposed system each component may be estimated as a multinomial logit model. Models are specified to reflect potential associations between individual activity-travel choices and such factors as time of day, socioeconomic characteristics, and history dependence. As an example results for activity type choice models estimated and validated with the 1990 Southern California Association of Governments travel diary data set are provided. The validation results indicate that the predicted pattern of activity choices conforms with observed choices by time of day. Thus, realistic daily activity-travel patterns, which are requisites for microsimulation approaches, can be generated for synthetic households in a practical manner.