Showing papers in "Transportation Research Record in 2005"

Laboratory Investigation of Mixing Hot-Mix Asphalt with Reclaimed Asphalt Pavement

Abstract: This paper presents a laboratory study in which the blending process of reclaimed asphalt pavement (RAP) with virgin mixture was analyzed through controlled experiments. One type of screened RAP was blended with virgin (new) coarse aggregate at different percentages. A blended mixture containing 20% of screened RAP was subjected to staged extraction and recovery. The result from this experiment indicated that only a small portion of aged asphalt in RAP actually participated in the remixing process; other portions formed a stiff coating around RAP aggregates, and RAP functionally acted as "composite black rock." The resulting composite layered structure was desirable to improve the performance of the hot-mix asphalt mixture.

Discrete choice with social and spatial network interdependencies: An empirical example using mixed generalized extreme value models with field and panel effects

Abstract: Discrete choice analysis has become an industry standard in land use and transportation models. Such models are fundamentally grounded in individual choice; therefore, the treatment of interdependencies among decision makers is a formidable challenge. Through an empirical application to mode choice, the capture of interdependencies in discrete choice is described and illustrated. Decision makers are assumed to be influenced, for example, by people of similar socioeconomic status who are nearby. Given such social and spatial network relationships, the choice model captures interdependencies in two ways: (a) including in the systematic utility variables that describe choices of others in the decision maker's social and spatial network and (b) allowing for correlation across the disturbances of decision makers within the same social and spatial network. Variations of these approaches (including their combination and the use of random parameters) are tested with mode choice and compared with traditional metho...

Investigation of the Fracture Resistance of Hot-Mix Asphalt Concrete Using a Disk-Shaped Compact Tension Test

Abstract: In recent years the transportation materials research community has focused a great deal of attention on the development of testing and analysis methods to shed light on fracture development in asphalt pavements. Recently it has been shown that crack initiation and propagation in asphalt materials can be realistically modeled with cutting-edge computational fracture mechanics tools. However, much more progress is needed toward the development of practical laboratory fracture tests to support these new modeling approaches. The goal of this paper is twofold: (a) to present a disk-shaped compact tension [DC(T)] test, which appears to be a practical method for determining low-temperature fracture properties of cylindrically shaped asphalt concrete test specimens, and (b) to illustrate how the DC(T) test can be used to obtain fracture properties of asphalt concrete specimens obtained from field cores following dynamic modulus and creep compliance tests performed on the same specimens. Testing four mixtures wit...

Split Models for Predicting Multivehicle Crashes During High-Speed and Low-Speed Operating Conditions on Freeways

Abstract: The future of traffic management and highway safety lies in proactive traffic management systems. Crash prediction models that use real-time traffic flow variables measured through a series of loop detectors are the most important component of such systems. A previous crash prediction model was developed with the matched case-control logistic regression technique. Although the model achieved reasonable classification accuracy, it remained open to improvement because of the limited study area, sample size, and transferability issues. Therefore, the previous work had been extended. Multivehicle freeway crashes under high- and low-speed traffic conditions were found to differ in severity and in their mechanism. The distribution of 5-min average speeds obtained immediately before the crash from the loop detector station closest to the crash shows two approximate mound-shaped distributions. This distribution is used as the basis to separate the models for crashes occurring under the two speed conditions. The results show that, as expected, variables that entered in the final models (for crashes under high and low speeds) were not the same. However, they were found to be consistent with the probable mechanisms of crashes under the respective speed conditions. A possible implementation of the separate models with the use of the odds ratios and with the balancing of the threshold between achieving high classification of crash potential and the false alarm situation is presented.

Analysis and Comparison of Microscopic Traffic Flow Models with Real Traffic Microscopic Data

Abstract: The evermore widespread use of microscopic traffic simulation in the analysis of road systems has refocused attention on submodels, including car-following models. The difficulties of microscopic-level simulation models in the accurate reproduction of real traffic phenomena stem not only from the complexity of calibration and validation operations but also from the structural inadequacies of the submodels themselves. Both of these drawbacks originate from the scant information available on real phenomena because of the difficulty with the gathering of accurate field data. In this study, the use of kinematic differential Global Positioning System instruments allowed the trajectories of four vehicles in a platoon to be accurately monitored under real traffic conditions on both urban and extraurban roads. Some of these data were used to analyze the behaviors of four microscopic traffic flow models that differed greatly in both approach and complexity. The effect of the choice of performance measures on the m...

Efficient Map Matching of Large Global Positioning System Data Sets: Tests on Speed-Monitoring Experiment in Zürich

Abstract: Speed and location observations from Global Positioning System (GPS) loggers are quickly becoming an important source of data for travel behavior researchers. Postprocessing these data requires identifying the location of the GPS data points on a coded map of the transportation network. The output of the map-matching process is the identification of the routes that were actually taken. This paper presents an innovative map-matching algorithm that relies only on the GPS coordinates and the network topology. Examples are provided on a large data set for the Zurich area. The paper demonstrates the efficiency of the algorithm in regard to accuracy and computational speed.

Application of the dissipated energy concept in fatigue endurance limit testing

Abstract: A fatigue endurance limit has been postulated to exist in hot-mix asphalt pavement performance It cannot be observed and studied with the use of traditional phenomenological approaches as seen by the totally different fatigue behavior at low strain-damage levels close to the fatigue endurance limit The ratio of dissipated energy change succeeds in defining and investigating the existence of a fatigue endurance limit with a unique relationship between plateau value (PV) and fatigue life (Nf), regardless of strain-damage levels, mixture types, loading modes, and other testing conditions To determine a fatigue endurance limit requires an extraordinarily long time to conduct testing This paper applied the PV to the study of a fatigue endurance limit to validate a shortened laboratory testing procedure Statistical analysis shows that the shortened test can predict the PV with sufficient accuracy By applying the validated relationship between PV and Nf, the extremely long fatigue life under low strain-dam

Advanced Testing and Characterization of Interlayer Shear Resistance

Abstract: The performance of multilayered pavement systems depends strongly on interlayer bonding. To guarantee good bonding, tack coats (also called bond coats) are usually applied at various interfaces during pavement construction or overlay. The effectiveness of the tack coat can be assessed with the use of several devices arranged by different laboratories to evaluate interlayer shear resistance. This paper shows how interlayer shear resistance may be evaluated through the Ancona shear testing research and analysis (ASTRA) device. ASTRA results, expressed in units of maximum interlayer shear stress (τpeak) highlight the effects of various influence parameters such as type of interface treatment, curing time, procedure of specimen preparation, temperature, and applied normal load. Moreover, this paper compares the τpeak results obtained by two different shear test devices: the ASTRA tester designed and developed in the Polytechnic University of Marche (Italy) and the layer-parallel direct shear tester created by...

Traffic Measurement and Vehicle Classification with Single Magnetic Sensor

Abstract: Wireless magnetic sensor networks offer an attractive, low-cost alternative to inductive loops for traffic measurement in freeways and at intersections. In addition to providing vehicle count, occupancy, and speed, these sensors yield information (such as non-axle-based vehicle classification) that cannot be obtained from standard loop data. Because such networks can be deployed quickly, they can be used (and reused) for temporary traffic measurement. This paper reports the detection capabilities of magnetic sensors on the basis of two field experiments. The first experiment collected a 2-h trace of measurements on Hearst Avenue in Berkeley, California. The vehicle detection rate was better than 99% (100% for vehicles other than motorcycles), and estimates of average vehicle length and speed appear to have been better than 90%. The measurements also yield intervehicle spacing or headways, revealing interesting phenomena such as platoon formation downstream of a traffic signal. Results of the second experiment are preliminary. Sensor data from 37 passing vehicles at the same site are processed and classified into six types. Sixty percent of the vehicles are classified correctly when length is not used as a feature. The classification algorithm can be implemented in real time by the sensor node itself, in contrast to other methods based on high-scan-rate inductive loop signals, which require extensive off-line computation. It is believed that if length were used as a feature, 80% to 90% of vehicles would be correctly classified.

Relating Adhesion and Cohesion of Asphalts to the Effect of Moisture on Laboratory Performance of Asphalt Mixtures

Abstract: Antistripping additives and polymer modifications are two common modifiers used to improve the fundamental properties of asphalt binders as those properties relate to the performance of asphalt mixtures Adhesion and cohesion are two important related properties of asphalt binders that can affect asphalt mixture performance before and after water conditioning The purpose of this study was to quantify the effects of antistripping additives and polymers on the adhesion and cohesion of binders and to relate these effects to the performance of mixtures as measured in the laboratory before and after water conditioning The performance tests of asphalt mixtures included indirect tensile strength, uniaxial compression permanent deformation, and Hamburg wheel tracking Asphalt mixtures were produced with different modified binders and with two aggregate types The binders were modified with antistripping additives and polymers and by chemical treatment and oxidization methods Granite and limestone were selected

Florida activity mobility simulator - Overview and preliminary validation results

Abstract: The development of modeling systems for activity-based travel demand ushers in a new era in transportation demand forecasting and planning. A comprehensive multimodal activity-based system for forecasting travel demand was developed for implementation in Florida and resulted in the Florida Activity Mobility Simulator (FAMOS). Two main modules compose the FAMOS microsimulation model system for modeling activity-travel patterns of individuals: the Household Attributes Generation System and the Prism-Constrained Activity-Travel Simulator. FAMOS was developed and estimated with household activity and travel data collected in southeast Florida in 2000. Results of the model development effort are promising and demonstrate the applicability of activity-based model systems in travel demand forecasting. An overview of the model system, a description of its features and capabilities, and preliminary validation results are provided.

Monitoring and Predicting Freeway Travel Time Reliability: Using Width and Skew of Day-to-Day Travel Time Distribution

Abstract: Generally, the day-to-day variability of route travel times on, for example, freeway corridors is considered closely related to the reliability of a road network. The more that travel times on route r are dispersed in a particular time-of-day (TOD) and day-of-week (DOW) period, the more unreliable travel times on route r are conceived to be. In the literature, many different aspects of the day-to-day travel time distribution have been proposed as indicators of reliability. Mean and variance do not provide much insight because those metrics tend to obscure important aspects of the distribution under specific circumstances. It is argued that both skew and width of this distribution are relevant indicators for unreliability; therefore, two reliability metrics are proposed. These metrics are based on three characteristic percentiles: the 10th, 50th, and 90th percentile for a given route and TOD-DOW period. High values of either metric indicate high travel time unreliability. However, the weight of each metric on travel time reliability may be application- or context-specific. The practical value of these particular metrics is that they can be used to construct so-called reliability maps, which not only visualize the unreliability of travel times for a given DOW-TOD period but also help identify DOW-TOD periods in which congestion will likely set in (or dissolve). That means identification of the uncertainty of start, end, and, hence, length of morning and afternoon peak hours. Combined with a long-term travel time prediction model, the metrics can be used to predict travel time (un)reliability. Finally, the metrics may be used in discrete choice models as explanatory variables for driver uncertainty.

Development and Evaluation of a Procedure for the Calibration of Simulation Models

Abstract: Microscopic traffic simulation models have been playing an important role in the evaluation of transportation engineering and planning practices for the past few decades, particularly in cases in which field implementation is difficult or expensive to conduct. To achieve high fidelity and credibility for a traffic simulation model, model calibration and validation are of utmost importance. Most calibration efforts reported in the literature have focused on the informal practice, and they have seldom proposed a systematic procedure or guideline for the calibration and validation of simulation models. This paper proposes a procedure for microscopic simulation model calibration. The validity of the proposed procedure was demonstrated by use of a case study of an actuated signalized intersection by using a widely used microscopic traffic simulation model, Verkehr in Staedten Simulation (VISSIM). The simulation results were compared with multiple days of field data to determine the performance of the calibrate...

Estimating Trip Generation of Elderly and Disabled People: Analysis of London Data

Abstract: The aging of populations has implications for trip-making behavior and the demand for special transport services. The London Area Travel Survey 2001 is analyzed to establish the trip-making characteristics of elderly and disabled people. Ordinal probit models are fitted for all trips and for trips by four purposes (work, shopping, personal business, and recreational), with daily trip frequency as the latent variable. A log-linear model is used to analyze trip length. A distinction must be made between young disabled, younger elderly, and older elderly people. Retired people initially tend to make more trips, but as they become older and disabilities intervene, trip making tails off. Household structure, income, car ownership, possession of a driver's license, difficulty walking, and other disabilities are found to affect trip frequency and length to a greater or lesser extent.

Validation of a Driving Simulator for Work Zone Design

Abstract: The research project aimed at calibrating and validating the driving simulator of the European Interuniversity Research Center for Road Safety to enable its use for design and verification of the effectiveness of temporary traffic signs on highways. The research was developed through the following steps: (a) a survey of speed measurements on highways next to a work zone of medium duration, (b) reconstruction in virtual reality of the real situation by using the driving simulator and subsequent running of a series of driving tests, and (c) statistical analysis of the field speeds and of the speeds from driving simulations for validation of the simulator. The surveyed work zone was located on Highway A1 from Milan to Naples, Italy. Speed measurements were conducted with a laser speed meter in the transition area, the activity area, and the termination area, and in the advance warning area speeds were shot with a camera from an overpass. Speed data from the field and the simulator were analyzed by using the bilateral Z-test for nonmatched samples to determine whether drivers responded differently in the simulator compared with their response during the real driving experience. The activity carried out revealed that differences between the speeds observed in the real situation and those measured with the simulator were not statistically significant.

Method for Automated Discontinuity Analysis of Rock Slopes with Three-Dimensional Laser Scanning

Abstract: Three-dimensional (3D) laser scanning data can be used to characterize discontinuous rock masses in an unbiased, rapid, and accurate manner. With 3D laser scanning, it is now possible to measure rock faces whose access is restricted or rock slopes along highways or railway lines where working conditions are hazardous. The proposed method is less expensive than traditional manual survey and analysis methods. Laser scanning is a relatively new surveying technique that yields a so-called point cloud set of data; every single point represents a point in 3D space of the scanned rock surface. Because the density of the point cloud can be high (on the order of 5 mm to 1 cm), it allows for an accurate reconstruction of the original rock surface in the form of a 3D interpolated and meshed surface using different interpolation techniques. Through geometric analysis of this 3D mesh and plotting of the facet orientations in a polar plot, it is possible to observe clusters that represent different rock mass discontinu...

PhillyCarShare : First-year social and mobility impacts of carsharing in philadelphia, pennsylvania

Abstract: One year into a carsharing program in Philadelphia, Pennsylvania, compelling evidence of reduced vehicle ownership, reduced vehicle miles traveled (VMT), and social change was uncovered through member surveys and detailed usage data. Each PhillyCarShare vehicle replaced an average of 23 private vehicles. Members giving up cars overwhelmingly reported driving less and replacing automobile trips with a variety of modes (transit, walking, taxi, and to a lesser extent biking). However, members who simply gained access to cars used PhillyCar-Share primarily to substitute for modes that most resemble driving (taxis, borrowing or renting, and to a lesser extent transit). The average monthly VMT increase of members gaining access to a car was limited to 29.9 mi, whereas the monthly VMT decrease of members who gave up a car appeared to be several hundred miles but not greater than 522 mi. After joining, PhillyCarShare members made travel decisions more judiciously, expressed greater awareness of transportation cos...

Structural Equation Modeling to Determine Passenger Loyalty Toward Intercity Bus Services

Abstract: This paper investigates passenger loyalty to intercity bus services and identifies important factors influencing loyalty. The relationships between passenger loyalty and other latent factors, including satisfaction, service value, service quality, sacrifice, switching costs, attractiveness of competitors, and trust are hypothesized and tested. Factor analysis is used to extract the latent service quality factors from a large number of service quality indicators. Structural equation models are then developed to elucidate the causal relationships of passenger loyalty and the latent factors. The empirical results have confirmed the proposed hypotheses. Satisfaction has the most significant influence on passenger loyalty. Service value, switching costs, and trust have direct and positive effects on loyalty, whereas attractiveness of competitors has a direct negative effect. The indirect effect of service quality, via service value and satisfaction, on passenger loyalty is also significant. From the empirical results, managerial implications for the bus carriers are addressed.

Development and Application of an International Vehicle Emissions Model

Abstract: Rapid vehicle growth in developing nations makes it necessary for these nations to address the transportation and environmental impacts of on-road mobile sources. To estimate the air quality impact of their fleets, many nations have adopted modified versions of U.S. or European emissions models or factors. In most cases, these models can lead to significant errors in emissions estimates. To address this problem, a new on-road mobile source emissions model, called the international vehicle emissions (IVE) model, designed for use in developing countries has been developed. The IVE model was developed jointly by researchers at the International Sustainable Systems Research Center and the University of California at Riverside. The IVE model uses local vehicle technology distributions, power-based driving factors, vehicle soak distributions, and meteorological factors to tailor the model to the local situation. In addition, an intensive 2-week field study was designed to collect the necessary fleet and activity data to populate the model with critical local information. The IVE model, along with the field study process, has proved highly effective in providing an improved estimate of mobile source emissions in an urban area and allows the effective analysis of local policy options. The studies have served to transfer tools and knowledge on the process of creating and improving mobile source inventories in an efficient manner. The rationale behind the development of the model, the development and application of the field studies, an overview of the results obtained to date, and planned next steps are described in this paper.

Metrics of Urban Form and the Modifiable Areal Unit Problem

Abstract: There is growing interest in incorporating urban form indicators into transportation planning and travel analysis. These indicators typically are measured at a certain level of spatial aggregation (e.g., traffic analysis zone) and therefore are subject to the modifiable areal unit problem (MAUP) known primarily in the statistical and geographic literature but generally overlooked by transportation researchers. The presence of the MAUP can cause serious inconsistency in analytical results and consequently misinform policy making. This study diagnoses the MAUP in measuring urban form through empirical modeling of travel mode choice in the Boston, Massachusetts, region. Using data aggregated in grids with five cell sizes and at the transportation analysis zone, the census block group, and the block level, the study explores the sensitivity of coefficient estimates for population density, network pattern, and land use balance to data aggregation in predicting mode choice decisions. Having confirmed the presen...

Alternative Risk Models for Ranking Locations for Safety Improvement

Abstract: Many types of statistical models have been proposed for estimating accident risk in transport networks, ranging from basic Poisson and negative binomial models to more complicated models, such as zero-inflated and hierarchical Bayesian models. However, little systematic effort has been devoted to comparing the performance and practical implications of these models and ranking criteria when they are used for identifying hazardous locations. This research investigates the relative performance of three alternative models: the traditional negative binomial model, the heterogeneous negative binomial model, and the Poisson lognormal model. In particular, this work focuses on the impact of the choice of two alternative prior distributions (i.e., gamma versus lognormal) and the effect of allowing variability in the dispersion parameter on the outcome of the analysis. From each model, two alternative accident estimators are computed by using the conditional mean under both marginal and posterior distributions. A sample of Canadian highway-railway intersections with an accident history of 5 years is used to calibrate and evaluate the three alternative models and the two ranking criteria. It is concluded that the choice of model assumptions and ranking criteria can lead to considerably different lists of hazardous locations.

Low Income, Public Transit, and Mobility:

Abstract: A fundamental justification for transit subsidies in the United States is to provide a basic level of mobility to all persons, especially the transportation disadvantaged: those who are either unwilling or unable to drive or who do not have access to a car. Yet even among the disadvantaged, most travel is by private vehicle. This paper examines the role of transit in the daily travel patterns of low-income households. Public transit is used for only a small portion of travel, and those who use transit regularly have the lowest level of mobility among all population segments. Attitudinal data indicate dissatisfaction with public transit, suggesting that current trends are likely to continue. Retaining existing markets by improving service frequency and quality in high-demand markets, exploring more effective ways of providing transit in low-demand markets, and expanding transit to serve off-peak and off-direction commutes would make transit a more attractive option for everyone.

Speed and Road Safety: Synthesis of Evidence from Evaluation Studies

Abstract: This paper presents a study evaluating the power model of the relationship between speed and road safety. The power model states that a given relative change in the mean speed of traffic is associated with a relative change in the number of accidents or accident victims by means of a power function. An extensive review of relevant literature has been made, and evidence from 98 studies containing 460 estimates of the relationship between changes in speed and changes in the number of accidents or accident victims has been synthesized by means of meta-analysis. The results are broadly supportive of the power model. It is concluded that speed has a major impact on the number of accidents and the severity of injuries and that the relationship between speed and road safety is causal, not just statistical.

Joint Modeling of Advanced Travel Information Service, Habit, and Learning Impacts on Route Choice by Laboratory Simulator Experiments

Abstract: A conceptual modeling framework is proposed, and mathematical sub-models for route choice on motorways and urban networks are derived. The models convey the most relevant aspects that play a role in route choice, including learning, risk attitude under uncertainty, habit, and the impacts of advanced travel information service on route choice and learning. To gain insight into the relative importance of the different aspects and processes of route choice behavior, which support the proposed conceptual framework, the models were estimated with data from two experiments carried out with a so-called interactive travel simulator. The latter is a new research laboratory that combines the advantages of both stated preference and revealed preference research. Many relevant contributions on the aforementioned aspects that play a role in route choice can be found in the literature, but a simultaneous consideration of all is lacking. On the basis of these contributions from the literature, a conceptual framework tha...

Mechanistic and Volumetric Properties of Asphalt Mixtures with Recycled Asphalt Pavement

Abstract: This research examines how the addition of recycled asphalt pavement (RAP) changes the volumetric and mechanistic properties of asphalt mixtures. A Superpave® 19-mm mixture containing 0% RAP was the control for evaluating properties of mixes containing 15%, 25%, and 40% RAP. Two types of RAP were evaluated: a processed RAP and an unprocessed RAP (grindings). Testing included dynamic modulus in tension and compression, creep compliance in compression, and creep flow in compression. Dynamic modulus and creep compliance master curves were constructed with the use of the time-temperature superposition principle to describe the behavior of each mix over a range of temperatures. The voids in mineral aggregate (VMA) and voids filled with asphalt (VFA) of the RAP mixtures increased at the 25% and 40% levels, and there was also an influence of preheating time on the volumetric properties. The dynamic modulus of the processed RAP mixtures increased from the control to 15% RAP level, but the 25% and 40% RAP mixtures...

Trip-Chaining Trends in the United States: Understanding Travel Behavior for Policy Making

Abstract: This paper uses data from the 1995 Nationwide Personal Transportation Survey and the 2001 National Household Travel Survey to examine trip-chaining trends in the United States. The research focuses on trip chaining related to the work trip and contrasts travel characteristics of workers who trip chain with those who do not, including their distance from work, current levels of trip making, and the purposes of stops made within chains. Trends examined include changes in the purpose of stops and in trip-chaining behavior by gender and life cycle. A robust growth in trip chaining occurred between 1995 and 2001, nearly all in the direction of home to work. Men increased their trip chaining more than women, and a large part of the increase was to stop for coffee (the Starbucks effect). It was found that workers who trip chain live farther from their workplaces than workers who do not. It was also found that, in two-parent, two-worker households that drop off children at school, women are far more likely than men to incorporate that trip into their commute and that those trips are highly constrained between 8:00 a.m. and 9:00 a.m. An analysis was done of workers who stopped to shop and those who did not but made a separate shopping trip from home; a large potential to increase trip-chaining behavior in shopping trips was found. Results of these analyses have important policy implications as well as implications for travel demand forecast model development. Finally, this paper uses these analyses to develop conclusions about the utility of transportation policies and programs that use the promotion of trip chaining as a primary travel demand management strategy.

Practical Procedure for Developing Dynamic Modulus Master Curves for Pavement Structural Design

Abstract: A dynamic modulus master curve for asphalt concrete is a critical input for flexible pavement design in the mechanistic-empirical pavement design guide developed in NCHRP Project 1-37A. The recommended testing to develop the modulus master curve is presented in AASHTO Provisional Standard TP62-03, Standard Method of Test for Determining Dynamic Modulus of Hot-Mix Asphalt Concrete Mixtures. It includes testing at least two replicate specimens at five temperatures between 14°F and 130°F (-10°C and 54.4°C) and six loading rates between 0.1 and 25 Hz. The master curve and shift factors are then developed from this database of 60 measured moduli using numerical optimization. The testing requires substantial effort, and there is much overlap in the measured data, which is not needed when numerical methods are used to perform the time-temperature shifting for the master curve. This paper presents an alternative to the testing sequence specified in AASHTO TP62-03. It requires testing at only three temperatures be...

Hybrid Mesoscopic-Microscopic Traffic Simulation

Abstract: Traffic simulation is an important tool for modeling the operations of dynamic traffic systems. Although microscopic simulation models provide a detailed representation of the traffic process, macroscopic and mesoscopic models capture the traffic dynamics of large networks in less detail but without the problems of application and calibration of microscopic models. This paper presents a hybrid mesoscopic-microscopic model that applies microscopic simulation to areas of specific interest while simulating a large surrounding network in less detail with a mesoscopic model. The requirements that are important for a hybrid model to be consistent across the models at different levels of detail are identified. These requirements vary from the network and route choice consistency to the consistency of the traffic dynamics at the boundaries of the microscopic and mesoscopic submodels. An integration framework that satisfies these requirements is proposed. A prototype hybrid model is used to demonstrate the application of the integration framework and the solution of the various integration issues. The hybrid model integrates MlTSIMLab, a microscopic traffic simulation model, and Mezzo, a newly developed mesoscopic model. The hybrid model is applied in two case studies. The results are promising and support both the proposed architecture and the importance of integrating microscopic and mesoscopic models.

Influence of Accessibility on Residential Location Choice

Abstract: There has been substantial discussion among planners about the influence of transport in residential location choices. The purpose of this paper is to analyze the importance of accessibility in explaining residential location choices. The paper addresses this issue by presenting and analyzing findings from the literature and results of a housing market estimation study in the Netherlands. The research findings for the Netherlands illustrate that the transport system influences residential moves at three stages: in move-stay choice, estimation results show that households are less likely to move away from a more accessible location; travel time variables are significant for all household types, and therefore changes in the transport system will affect the size of the housing market and search area of the households; the model estimation results suggest that accessibility of a specific location for many household types is not a significant variable in their location choice. Overall, the empirical results suggest that the role of accessibility is significant but small compared with the effect of demographic factors, neighborhood amenities, and dwelling attributes in explaining residential location choices. The empirical findings are confirmed by findings in the literature; the present results are located at the lower end of findings reported in the literature. An important factor contributing to this result is that accessibility changes among regions in the Netherlands are rather small.

Analysis of Day-to-Day Variability in an Individual's Action Space: Exploration of 6-Week Mobidrive Travel Diary Data

Abstract: Using 6-week travel diary data from Karlsruhe and Halle, Germany, this study examines the characteristics of individuals' action space. The extension of action space is represented by the second moment of the activity locations that it contains. Day-to-day variation in the second moment is examined. The results show that out-of-home activity orientation and commitment (e.g., obligatory activities on weekdays and discretionary activities on weekend days) influence the extension of action space. For workers and students on weekdays, the spread of activity locations and the distance from home to the centroid of activity locations are relatively stable from day to day. A substantial portion of the variations in their action spaces is due to unexplained differences across individuals that remain stable over time for each individual (unobserved heterogeneity). In contrast, random factors have dominant influences on nonworkers' weekday action spaces and on all individuals' weekend action spaces.