The shortest path usually isn’t the best one, according to bikeshare users

By Chris McCahill

Many transportation models assume that people choose the shortest (or least cost) path connecting them from point A to point B. But this isn’t how individuals actually behave—or so confirms one recent study based on bikeshare trip data. This affects how we model travel behavior, but also our understanding of people’s travel preferences and the ways in which we accommodate them.

For this newest study, researchers at McMaster University in Ontario, Canada, used on-board GPS data to compare actual SoBi (Social Bicycles) trips to their corresponding shortest distance paths. They found that the most popular route between any pair of SoBi hubs was 10 percent less efficient than the shortest path, measured in terms of route directness. The shortest path was the most popular choice for only seven percent of hub pairs.

A similar pattern also holds true for driving trips, as highlighted in the most recent National Household Travel Survey. The newest 2017 survey used Google API to estimate trip distances based on shortest path algorithms, but the survey documentation warns that these distances could be 10 percent lower than self-reported distances in previous surveys.

The reasons for longer bike trips could be much more telling, however. It is not surprising, for example, that SoBi users traveled longer distances on grades below four percent, to avoid steeper slopes. They also preferred local roads over major ones and chose routes with designated bike lanes. This kind of information, articulated by the level of traffic stress concept for bicycle networks, can inform bicycle plans, infrastructure prioritization and maintenance, and bicycle accessibility analysis, which was highlighted in a recent SSTI webinar.

Chris McCahill is the Deputy Director at SSTI.