JAKARTA, Indonesia — Even on the best of days, it looks like an invasion, though a very slow one: Troops of motorbikes, like a disorganized cavalry, try to slice through enormous, honking lines of buses, trucks, private cars and taxis that are locked in a crawling war of attrition on sclerotic highways and roads.

The war zone extends to sidewalks, a convenient shortcut for impatient motorbike drivers, and pedestrians and food cart vendors disrupt the traffic flow even more by illegally crossing the thoroughfares.

The traffic tie-ups get especially hellish during the morning and evening rushes. That is true in most urban areas, but especially so in a city like Jakarta, which is at the center of a metropolitan area of 28 million people and whose population of 10 million swells by some three million every workday.