Browsing by Subject "activity duration"

Now showing 1 - 5 of 5

A continuous time representation and modeling framework for the analysis of nonworker activity-travel patterns: Tour and episode attributes
(Transportation Research Board of the National Academies, 2003) Misra, Rajul; Bhat, Chandra R.; Srinivasan, Sivaramakrishnan
This paper presents a set of four econometric models to examine the tour and episode-related attributes (specifically mode choice, activity duration, travel times, and location choice) of the activity-travel patterns of non-workers. The paper is a sequel to an earlier work by the authors [see Bhat and Misra (1)], which presented a comprehensive continuous-time framework for representation and analysis of the activity-travel choices of non-workers. That paper also presented detailed descriptions of the first two components of the modeling framework related to the number and sequence of activity episodes. The current paper estimates the proposed models using activity-travel data from the 1990 San Francisco Bay Area travel diary survey.
An Econometric Multi-Dimensional Choice Model of Activity-Travel Behavior
(Maney Publishing, 2010) Eluru, Naveen; Pinjari, Abdul R.; Pendyala, Ram M.; Bhat, Chandra R.
Recent evidence suggests that many activity-travel choices are inter-dependent with one another and hence inextricably linked in ways that need to be better understood to help inform the specification of activity-based travel model systems. Model systems in practice often sequentially link a series of choice dimensions into a deeply nested logit model where accessibility variables (logsum terms) from lower nests cascade up through the structure to the higher levels in the model structure. While these model systems are convenient from a practical standpoint, they ignore the potential jointness in choice-making processes and do not effectively and directly capture the effects of spatial land use and built environment characteristics on activity generation. In this paper, a unified model of activity type choice (generation), time of day choice, mode choice, destination choice, and time use allocation (duration) is formulated and estimated on a survey sample data set drawn from the 2000 San Francisco Bay Area Travel Survey (BATS). The model system constitutes a joint multiple discrete continuous extreme value (MDCEV) multinomial logit (MNL) model, in which all discrete choices, except for destination choice, and the continuous duration dimension are modeled using the MDCEV, and destination choice is modeled as a MNL (with sampling of alternatives) nested and therefore integrated with the MDCEV model component. The parameter estimates of the joint model offer behaviorally intuitive results that support the integrated treatment of these choice dimensions as a choice bundle. The potential applicability of the model system is demonstrated through a policy simulation example that shows how changes in travel cost and time variables lead to changes in out-of-home discretionary activity participation.
An Exploration of the Relationship Between Timing and Duration of Maintenance Activities
(Springer, 2004) Pendyala, Ram M.; Bhat, Chandra R.
The timing and duration of an activity episode are two important temporal aspects of activity travel behavior. Understanding the causal relationship between these two variables would be useful in the development of activity-based travel demand modeling systems. This paper investigates the relationship between these two variables by considering two different causal structures - one structure in which time-of-day choice is determined first and influences duration and a second structure in which activity duration is determined first and affects time-of-day choice. These two structures are estimated within a discrete-continuous simultaneous equations framework employing a full-information maximum likelihood methodology that allows error covariance. The estimation is performed separately for commuter and non-commuter samples drawn from a 1996 household travel survey data set from the Tampa Bay area in Florida. The results of the model estimation effort show that the causal structure in which activity duration precedes or affects activity timing (time of day choice) performs better for the non-commuter sample. For the commuter sample, the findings were less conclusive with both causal structures offering equally good statistical measures of fit. In addition, for the commuter sample, all error correlations were found to be zero. These two findings suggest that time of day choice and activity episode duration are only loosely related for the commuter sample, possibly due to the relatively non-discretionary and inflexible work activity and travel.
A hazard-based duration model of shopping activity with nonparametric baseline specification and nonparametric control for unobserved heterogeneity
(Elsevier, 1996) Bhat, Chandra R.
Activity duration is an important component of the activity participation behavior of individuals, and therefore, an important determinant of individual travel behavior. In this paper, we examine the factors affecting shopping activity duration during the return home from work and develop a comprehensive methodological framework to estimate a stochastic hazard-based duration model from grouped (interval-level) failure data. The framework accommodates a nonparametric baseline hazard distribution and allows for nonparametric control of unobserved heterogeneity, while incorporating the effects of covariates. The framework also facilitates statistical testing of alternative parametric assumptions on the baseline hazard distribution and on the unobserved heterogeneity distribution. Our empirical results indicate significant effects of unobserved heterogeneity on shopping activity duration of individuals. Further, we find that parametric forms for the baseline hazard and unobserved heterogeneity distributions are inadequate, and are likely to lead to substantial biases in covariate effects and hazard dynamics. The empirical results also provide insights into the determinants of shopping activity duration during the commute trip.
Modeling the Influence of Family, Social Context, and Spatial Proximity on Use of Nonmotorized Transport Mode
(National Academy of Sciences, 2011) Ferdous, Nazneen; Pendyala, Ram M.; Bhat, Chandra R.; Konduri Karthik C.
This paper presents a joint model of walking and bicycling activity duration using a hazard based specification that recognizes the interval nature of time reported in activity-travel surveys. The model structure takes the form of a multilevel hazard-based model system that accounts for the range of interactions and spatial effects that might affect walking and bicycling mode use. In addition to the individual-specific factors, family (household-specific) interactions, social group (peer) influences, and spatial clustering effects are also considered as potential factors that contribute to heterogeneity in non-motorized transport mode use behavior. The model system presented is capable of accommodating grouped duration responses often encountered in activity-travel surveys. A composite marginal likelihood estimation approach is adopted to estimate parameters in a computationally tractable manner. The model system is applied to a survey sample drawn from the recent 2009 National Household Travel Survey in the United States. Model results show that there are significant unobserved family-level, social group, and spatial proximity effects that contribute to heterogeneity in walking and bicycling activity duration. The unobserved effects were also found to have a differential impact on bicycling activity duration, thus suggesting the need to treat and model walking and bicycling separately in transportation modeling systems.