“My First Four Step Model” is a simple four-step model that can install easily and run quickly on consumer-grade computers. It can be estimated for any US metropolitan area using publicly-available data.
Most transportation planning and engineering programs teach travel demand modeling to some extent. In my experience, it is almost invariably taught with a ‘bottom-up’ approach. Students take classes on transportation planning, econometrics, and choice modeling. Students then work with individual components of demand models, such as trip generation or mode choice. Often, students never “put it all together” to run a regional model from start to finish. The vast majority of learning time is spent on theory and mathematics, rather than applications. My First Four Step Model facilitates a ‘top-down’ approach where running a complete model is one of the first steps. I use this approach in my introductory Planning Methods course, where we spend only a week discussing transportation modeling and engineering, and at the conclusion the students run a simple demand model for the Research Triangle region of North Carolina. Full details of this learning module are available here.
Theory and mathematics are paramount for those who will build and run travel demand models themselves. This is a very small group of students, however. At most metropolitan planning organizations and DOT’s, demand models are estimated and run by consultants or a small in-house team. Consumers of model output are a larger group: transportation planners and engineers, land use planners, developers, advocates, and so on. For this larger group, only a cursory understanding of the mathematics is required; the general mechanisms and assumptions the model relies on are far more important.
Most students in transportation planning and engineering programs will fall into the latter group. A better understanding of modeling among this group will help promote better communications between modelers and model consumers. Consumers will be more aware of what the model can and can’t do, and more able to come up with situations where the model may be helpful. Understanding will also promote a “healthy skepticism” of the model, enabling feedback from users on the model and ultimately leading to better models and decision support.
Students interested in modeling may take further classes, but all students will have some first-hand experience with demand models—something many students do not get at all today, even after taking many classes on modeling.
My First Four-Step Model will never be appropriate for production travel demand modeling. It is also not appropriate as a sole teaching tool for students who will ultimately become modelers. However, it is useful as a first exercise even in courses that focus only on demand modeling, where students can have a chance to work with a simple model before diving into the more complex theories and software that are necessary for a detailed education in this area.