Organized traffic generally has well-established priorities, lanes, right-of-way, and traffic control at intersections.

Organization

Traffic is formally organized in many jurisdictions, with marked lanes, junctions, intersections, interchanges, traffic signals, or signs. Traffic is often classified by type: heavy motor vehicle (e.g., car, truck); other vehicle (e.g., moped, bicycle); and pedestrian. Different classes may share speed limits and easement, or may be segregated. Some jurisdictions may have very detailed and complex rules of the road while others rely more on drivers' common sense and willingness to cooperate.

Organization typically produces a better combination of travel safety and efficiency. Events which disrupt the flow and may cause traffic to degenerate into a disorganized mess include: road construction, collisions and debris in the roadway. On particularly busy freeways, a minor disruption may persist in a phenomenon known as traffic waves. A complete breakdown of organization may result in traffic jams and gridlock. Simulations of organized traffic frequently involve queuing theory, stochastic processes and equations of mathematical physics applied to traffic flow.

Rules of the road

main: Traffic code

As a general rule, drivers are expected to avoid hitting other vehicles and pedestrians, regardless of whether or not the applicable rules of the road allow them to be where they happen to be.

In addition to the rules applicable by default there are traffic signs, including traffic lights, and instructions may be given by a police officer, either routinely on a busy crossing instead of traffic lights, or as road traffic control around a construction zone, accident or other road disruption.

These rules should be distinguished from the mechanical procedures required to operate one's vehicle. See driving.

Directionality

main: Traffic directionality Traffic going in opposite directions should be separated in such a way that they do not block each other's way. The most basic rule regarding this concept is which side of the road should be used for travel. About 34% of the world by country population drives on the left, and 66% keeps right.Fact: date=April 2008 By roadway miles, about 72% drive on the right.Fact: date=April 2008

Highway code

In many countries, the rules of the road are codified, setting out the legal requirements and punishments for breaking them.