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Joint Travel Design
In the current example model, joint travel for non-mandatory activities is modeled explicitly in the form of fully joint tours (where all members of the travel party travel together from the very beginning to the end and participate in the same activities along the way). This accounts for more than 50% of joint travel. Other types of joint travel like carpooling of workers and escorting children are not explicitly considered currently, though they are handled implicitly through shared ride alternatives in mode choice. Some later versions of CT-RAMP implemented in specific regions better model joint travel, but for now, the example follows the MTC TM1 design.
The new sub-models are:
- Joint tour frequency
- Joint tour party composition
- Joint tour person participation
- Joint tour primary destination choice
- Joint tour time-of-day choice (i.e. scheduling)
- Joint tour mode choice
- For each household
- MNL model
- Alternatives: 21 (No Tours, 1 Tour segmented by purpose, 2 tours segmented by purpose combination)
- Notes:
- Includes the presence and size of overlapping time-windows, which represent the availability of household members to travel together after mandatory tours have been generated and scheduled.
- Relatively straightforward model and should be easily vectorized.
- For each joint tour
- MNL model
- Alternatives: 3 (Adults-only, Children-only, Adults + Children)
- Notes:
- Include the maximum time window overlaps across adults, children and adults or children after mandatory tours have been scheduled.
- The joint tour party composition model is relatively straightforward and should be easily vectorized.
- For each joint tour and person
- MNL model
- Alternatives: 2 (Participate in joint tour or does not participate in joint tour)
- Notes:
- Persons with CDAP=Home are excluded
- Requires the calculation of available person time windows
- The Java model loops through household persons until a valid tour party is formed. Within the valid tour party loop, a switch statement based on the party composition sets up and solves the relevant expression file for a) adults only, b) children only, or c) mixed, adults and children. After solving the relevant model, it checks for a valid party and if not, it then repeats the participation choice with new random numbers.
- Vectorizing the model requires re-structuring the problem into a series of pandas tables with rows being joint tours and columns being explanatory variables, including those for each person potentially being added to the joint tour. This is a switch from a for loop within each tour to a for loop that operates on each potential joint tour party.
- For each joint tour
- MNL model
- Alternatives: Zones
The joint tour primary destination choice model uses the existing tour non-mandatory destination choice model.
The joint tour scheduling model is similar to the existing other partially implemented scheduling models. It requires time windows and logsums.
The joint tour mode model uses the existing tour mode choice model.