By the Book: Is Induced Travel Missing from Transportation Engineering Textbooks?

Induced travel is the new travel that materializes in the aftermath of an expansion of transportation infrastructure (e.g., a wider road). Accounting for induced travel is essential for accurately describing the long-term benefits and environmental impacts of a project. However, engineers rarely account for induced travel during project planning and design, in part due to unfamiliarity with or skepticism about induced travel. To probe this missing piece of engineering practice, this research focuses on whether transportation engineering textbooks introduce students to the concept of induced travel. Based on a systematic review of seven textbooks, coverage of induced travel appears incomplete. Some textbooks omitted the idea entirely and those that did include it offered only partial coverage. Textbooks either defined the term, indicated its expected magnitude, used the concept in a problem set, or described the implications for practice and policy. However, no single textbook included all these essential elements. Beyond this, all textbooks placed a greater emphasis on accommodating demand rather than managing it. Textbooks offered an asymmetric portrayal of how drivers adjust to traffic conditions. They tended to emphasize that drivers avoid congested areas and de-emphasized that drivers are also attracted to uncongested routes. In short, the engineering textbooks reviewed here leave students unprepared to understand induced travel or its implications. To improve, teaching materials should: 1) clearly define induced travel and distinguish it from other terms, 2) indicate the expected magnitude of induced travel, 3) feature the concept in problem sets to be consistent with engineering's signature pedagogy, 4) describe the implications of induced travel for engineering practice, and 5) introduce students to foundational debates about transportation policymaking.