Traffic

In many parts of the world traffic is generally organized, flowing in lanes of travel for a particular direction, with interchanges, traffic signals, or signage at intersections to facilitate the orderly and timely flow of traffic. Traffic can be separated into vehicular, non-vehicular (bicycling), and pedestrian classes of traffic. Vehicles of the same class share their speed limits and share easement with one another. Cooperative signaling arrangements can also be made with representatives of other classes of traffic.

Right of Way ("who goes first")

Vehicles will often come into conflict with other vehicles because their intended courses of travel intersect, that is, they get in each other's way. The general principle that establishes who has the right to go first is called "right of way". It establishes who has the right to use the conflicting part of the road and who has to wait until the other driver does so.

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Different countries have different rules that establish who has the right of way, but a common pattern is for one of the roads (usually the smaller road) to have a marking indicating that it should "yield" to drivers on the other road. This can be in the form of a STOP sign, dotted lines painted on the pavement or other devices. Drivers approaching from the road with the STOP sign (or equivalent device) are required to stop before the intersection and only proceed when a breach occurs in the other road's traffic. Some countries also include pedestrian crossings near the STOP signs, and in this case the approaching drivers must also allow the pedestrian to cross the street before advancing.

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Another way to resolve the right-of-way conflict is to establish a general rule such as the French prioritè-a-droit (priority to the right). This rule establishes that the right of way belongs to the driver who is coming from the right, and the driver coming from the left should yield to him. This rule is unambiguous, but may lead to some counterintuitive situations, such as in T-intersections, where, strangely enough, traffic going straight through the top segment of the T must yield to entering traffic that comes from the vertical leg of the T.

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In most modern cities the traffic signal is used to establish the right of way on the busy roads. Its primary idea is to give each road a slice of time in which its traffic may use the intersection in an organized way. The intervals of time assigned for each road may be adjusted to take into account factors such as difference in volume of traffic.

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