At low density, ants move at a speed that maximizes efficiency. At medium density, they move a bit more briskly, sacrificing some energy to keep from blocking t

At low density, ants move at a speed that maximizes efficiency. At medium density, they move a bit more briskly, sacrificing some energy to keep from blocking traffic. At high density, they move more deliberately, avoiding situations like we see on highways where a single vehicle advances rapidly but slows down many others as they brake to avoid it and cause a traffic wave.