Public Release: 

Collective clog control: What ants can teach us about traffic flow

American Association for the Advancement of Science

Observing how ants excavate their narrow underground tunnels provides new insight into how to orchestrate optimal traffic flow in confined and crowded environments, researchers say. In ants, the researchers report, behaviors such as idleness or retreating lead to optimal excavation, reducing crowdedness and flow-stopping clogs. The results reveal strategies through which large groups of task-oriented beings could move more efficiently through confined spaces. Humans in cars confined to four lanes of a freeway is representative of how the flow of groups of things can form problematic clusters. This can in turn slow or even halt movement through a system. Though social insects like ants routinely perform tasks - such as excavating narrow tunnels - that demand a steady flow, they somehow rarely form flow-stopping clogs. To better understand how task-oriented active matter systems avoid detrimental clusters, Jeffrey Aguilar and colleagues monitored the movements of individual fire ants as they excavated. Aguilar et al. identified that certain behaviors, like low activity (idleness) or moving from the excavated tunnel to the nest's exit without removing any material (a move known as a "reversal"), reduced the prevalence and severity of clogs. What was also important to avoiding clogs was an unequal distribution of work, say the authors, with a percentage of ants doing most all of the labor. Using a cellular automata (CA) excavation model, the authors confirmed these behaviors' positive effect on excavation performance. Aguilar et al. then applied these concepts to a system of excavating robots to determine if the behaviors could be used to improve traffic in a robophysical model. Though the robots underperformed relative to the ants and the CA model, likely due to their limited mobility, the results from the related analysis do suggest ways in which dense groups can become "task capable," without getting in their own way. The strategies Aguilar's team has identified will be important in efforts to improve the movement of future engineered systems, like robot swarms tasked with removing disaster rubble, or nanorobots coursing through a bloodstream, say the authors.

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