May 8, 2013
People Navigate Their City Routes Efficiently And Predictably
Brett Smith for redOrbit.com - Your Universe Online
Personal vehicles and public transportation allow for individuals to select from a multitude of routes while making their routine daily commute. According to a new study in the“¯Journal of the Royal Society Interface, most people deviate from their regular commute in a fairly predictable and efficient pattern.
Using a “big data” analysis, MIT researcher Marta GonzÃ¡lez and her team were able to uncover motifs that occur with regular frequency.
“The existence of a motif means our predictive model can be based on a relatively simple mathematical formula rather than on more complex econometrics that try to account for all the different types of human behavior,” said GonzÃ¡lez, a professor in MIT´s Department of Civil and Environmental Engineering (CEE).
“For a physicist, this is key. With our model, we can now add drops of complexity — such as the types of secondary locations — to get a more complete picture.”
In reacting to Gonzalez´s study, physics professor Chaoming Song of Northeastern University said his experience in studying human mobility and complex networks inclines him to agree with GonzÃ¡lez´ findings.
“When working at the large scale you assume that everything is random. The motif captures the failure of that assumption, and for network scientists, this indicates a successful theory,” Song said. “GonzÃ¡lez and [colleagues] have derived a simple formula, which indicates the study has achieved a very deep understanding of the phenomena and that it has predictive power.”
“But the real beauty of their model is that it connects two layers,” he added. “It tells how individuals behave, yet is simple enough to use at the large-scale, population level.”
Study co-author Christian Schneider describes the model as a “perturbation model.”
“Once a person does a single ℠flexible´ trip beyond the primary commute, they are 10 times more likely to make an additional flexible trip rather than going directly back home. So I say they´re in a perturbed state,” Schneider explained.
For example, if a person travels from work to a restaurant, there is a greater chance they will then go somewhere else for dessert or coffee than there would be if they had opted to go straight home.
The MIT researchers also found that the number of potential trip configurations increased exponentially with each additional stop. However, the number of configurations that were actually used did not increase significantly, if at all.
For example, during a three-location trip only three of five possible configurations are typically used. For a four-stop trip, only four of the 83 possible configurations are used and with five stops, people only used an average of four of the 5,408 possible route combinations.
Schneider said the study demonstrates the planning and efficiency the goes into how people move around large cities such as Chicago or Paris. People tend to avoid going home between locations and, people seem to plan ahead to avoid revisiting a location — making travel more efficient and reducing wasted time.
“The motifs tell us that people seem to travel quite efficiently,” Schneider said.