1. Model Task Force Meeting November 29, 2007 Activity-based Modeling from an Academic Perspective Transportation Research Center (TRC) Dept. of Civil & Coastal Engg. University of Florida Siva Srinivasan

2. Overview 1.A critique of the trip-based method 2.What is the activity-based approach? 3.Feasibility of adopting activity-based methods 4.Concluding thoughts Model Task Force Meeting November 29, 2007

3. Home Work Lunch Shop Drop-off Kid at School 7:15 am 7:30 am 8:00 am 7:35 am 12:30 pm 12:35 pm 1:00 pm 1:05 pm 5:00 pm 5:30 pm6:00 pm 6:30 pm Car-pool Drive- alone walk Consider the travel pattern of a person……… Critique of the Trip-based Approach

4. Drive Walk HA1 H P3 P4 P5 P6 A2 A3 A4 A5 A6 One Home-based Other tripFour Non home-based trips Peak Off Peak Critique of the Trip-based Approach The trip-based method views this person’s travel as: Model Task Force Meeting November 29, 2007 One Home-based Shop trip

5. Trip Generation (frequency) Trip Distribution (destination) Mode Split (mode) Network Assignment (route) Link flows, speeds, travel times, transit- ridership, etc. Socio-economic characteristics Land-use patterns Transportation system characteristics Model Task Force Meeting November 29, 2007 The analytical modeling procedure is the “four-step” process Critique of the Trip-based Approach

6. The fundamental role of travel-demand models is to enable us perform quantitative assessments of the impacts of policy actions The policy actions being considered these days may invoke complex behavioral responses from travelers which cannot be adequately captured within a trip-based framework Some Illustrative Examples….. Model Task Force Meeting November 29, 2007 Critique of the Trip-based Approach

7. Example 1: Effect of Transit Improvements Model Task Force Meeting November 29, 2007 Work Shopping Drive alone Very Good Transit Service Transit Drive Alone Critique of the Trip-based Approach

8. Home WorkShop Example 2: Effect of Transit Improvements (alternate responses) Drive alone Home Shop Drive alone Home Work Transit Model Task Force Meeting November 29, 2007 Critique of the Trip-based Approach

9. 5:00 pm 5:15 pm5:40 pm 6:00 pm 4:00 pm 4:15 pm4:40 pm5:00 pm 4:00 pm 4:30 pm5:40 pm 6:00 pm Example 3: Employer-based Demand-Management Actions Model Task Force Meeting November 29, 2007 Critique of the Trip-based Approach

10. Home Work Pick-up child Shop Drop-off child Person 1 Person 2 Example 4: Inter-personal Dependencies and Indirect Effects Model Task Force Meeting November 29, 2007 Critique of the Trip-based Approach

11. Home Work Person 1 Pick-up child Shop Drop-off child Person 2 Model Task Force Meeting November 29, 2007 Critique of the Trip-based Approach Example 4: Inter-personal Dependencies and Indirect Effects

12. What is the Activity-based Approach? Model Task Force Meeting November 29, 2007 Home Work Lunch Shop Drop-off Kid at School 7:15 am 7:30 am 8:00 am 7:35 am 12:30 pm 12:35 pm 1:00 pm 1:05 pm 5:00 pm 5:30 pm6:00 pm 6:30 pm Car-pool Drive- alone walk The activity-based method views the travel pattern as………

13. Model Task Force Meeting November 29, 2007 The conceptual modeling procedure is……… (1) Activity Generation: Choose what out-of-home activities have to be undertaken during the day incorporating relevant constraints Drop-off Kid at School Work Lunch Shop Space constraints: Location of home, school, and work are fixed Time constraints: School and work timings Total time = 24 hours & that includes time for sleeping, eating etc. Inter-personal constraints: Household task allocations Joint travel of household members What is the Activity-based Approach?

14. Model Task Force Meeting November 29, 2007 The conceptual modeling procedure is……… (2) Activity Scheduling: Sequence the activities into a “chain” or “pattern”. Travel is a consequence of this sequencing – the need to move from one location to another at certain times of the day to participate in the different activities Home Work Lunch Shop Drop-off Kid at School 7:15 am 7:30 am 8:00 am 7:35 am 12:30 pm 12:35 pm 1:00 pm 1:05 pm 5:00 pm 5:30 pm6:00 pm 6:30 pm Car-pool Drive- alone walk Home School 7:15 am 7:30 am Car-pool 4:00 pm 4:15 pm Car-pool What is the Activity-based Approach?

15. Contrasting Trip-based and Activity-based Methods: Summary of Conceptual Differences Model Task Force Meeting November 29, 2007 Treatment of travel as though demanded on their own right Individual trip is the unit of analysis Internal consistency of the travel pattern NOT guaranteed Impacts of personal and household constraints not captured Represents time as simply a cost of making a trip and time-of-day of travel is not captured adequately Treatment of travel as a derived demand Activity-travel pattern is the unit of analysis Ensures internal consistency of the activity-travel pattern Accommodates the impacts of various constraints on activity-travel decision making Models travel within the context of overall daily time-use (both durations and time-of-day) Trip-based Activity-based

16. Contrasting Trip-based and Activity-based Methods: Summary of Modeling Differences Model Task Force Meeting November 29, 2007 Trip-based Activity-based Number of HB and NHB trips Generation and sequencing of activities Zonal-level trip attractions & gravity model for trip-end locations Location of activity participation Mode for each tripMode for linked trips (tours) Time of day using peak and off- peak factors Duration and timing of activities and travel

17. Feasibility of Adopting Activity-based Methods Model Task Force Meeting November 29, 2007 (1) Activity-based models are “complicated” Yes…  There are several (definitely more than four) components in the model-system  Could employ advanced econometric methods However…  The conceptual modeling approach is more intuitive and easier to explain  The overall complexity depends on what dimensions of the activity pattern we are modeling  Statistical software to estimate the advanced econometric models available

18. Model Task Force Meeting November 29, 2007 (2) Activity-based models are data intensive Yes…  Household travel surveys are needed for model estimation  Disaggregate forecasts of future population characteristics needed for model application However….  Activity-based models can be developed using data collected from currently-used household-travel-survey methods  In fact, activity-based methods make better use of the data we are currently collecting  Methods (Iterative Proportional Fitting) for synthesizing disaggregate population characteristics are available Feasibility of Adopting Activity-based Methods

19. Model Task Force Meeting November 29, 2007 (3) Activity-based models are computationally demanding Yes….  More model components / disaggregate approach / probabilistic models requiring micro-simulation to determine choice outcomes  Requires significant run times and very large data processing capabilities However…  Computers are only becoming faster !  Parallel processing, multi-threading, efficient database management methods are available  Can use clever sampling techniques Feasibility of Adopting Activity-based Methods

20. Model Task Force Meeting November 29, 2007 (4) There are no standardized procedures or software Yes…  Unlike the trip-based approach, there is no one single well-established procedure for modeling activity-patterns  There are no rigorous comparative assessments of the different modeling methods  There are no generic software platforms for implementing activity-based methods However…  There are common underlying structures across the different activity-based models that can provide guidelines on developing one for any region  There is considerable flexibility in customizing the modeling approach for the activity-travel dimensions of interest for any region Feasibility of Adopting Activity-based Methods

21. Model Task Force Meeting November 29, 2007 (5) Other Issues  Activity-based models have predominantly focused on internal, person travel – external travel and freight movements are not yet within this framework  The activity-patterns have to be aggregated to OD trip tables by time-of-day if dynamic traffic assignment techniques are to be used -- these may not necessarily be straight forward  Still need to make the models “empirically” useful Incorporation of appropriate traveler characteristics Choice of resolution for space and time Inclusion of appropriate land-use descriptors Inclusion of appropriate transportation system descriptors Feasibility of Adopting Activity-based Methods

22. Concluding Thoughts Model Task Force Meeting November 29, 2007 Activity-based methods are theoretically and intuitively better descriptors of the travel-generation process The fundamental advantage of activity-based approach is in terms of more providing more realistic behavioral responses to land-use and transportation system changes The practical necessity of activity-based methods (and the structure of this model) for any region depends on what kinds of questions we want the travel-demand model to answer for this region It does appear that the “questions” are rather different for different regions as are data and resource availability Customization of the modeling methodology to different regions is more appropriate ??