“Low-incidence” travel behavior is difficult to capture in a
traditional household travel study (where typically one day of travel is
collected from a representative sample of households in a region). Behaviors or
travel choices that do not occur frequently may fall into different categories:
· Behaviors that a small number of people
participate in or consider in their travel choice set. This might include
travel modes that are used frequently by a small number of people (bicycling,
vanpool, etc.) or new or emerging travel modes that may not be widely used yet
(carshare, rideshare, e-bikes, automated vehicles, etc.)
· Travel behavior in the context of complex
analytical structures (complicated tour patterns, decisions that are related to
· Behaviors that a large number of people may
participate in, but may not engage in frequently enough to be captured in a
one-day travel diary (long-distance travel, trip replacement behavior such as
home delivery of goods and services, etc.)
It is important to be able to collect more observations of
these behaviors to better analyze the current and future demand for different
types of travel; to better understand how these rare or new types of behaviors
affect the overall demand for transportation resources; and to understand how
these emerging alternatives may affect “traditional” transportation behavior.
Because these behaviors are rare, alternative methods for sampling enough
observations in a regional travel study need to be identified and tested.
Despite their low-incidence, many of these alternatives have outsize effects on
the transportation system.
It should also be noted that some behaviors are related to
more to survey design than to sampling -
for example, it may be easy to sample the types of people who participate in
long-distance travel, but a multi-day survey design or other survey design may
be better for capturing these trips which may occur infrequently. The variety
of challenges in observing different types of rare behaviors may necessitate
separate and distinct research efforts to focus on methods that address the
primary challenges for a given type of behavior.