Traffic

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Traffic refers to the movement of motorized vehicles, unmotorized vehicles and pedestrians on roads. Traffic laws are the laws which govern traffic and regulta vehicles, while rules of the road are both the laws and the informal rules that may have developed over time to facilitate the orderly and timely flow of traffic.

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

Organization

In many parts of the world traffic is generally organized, flowing in lanes of travel for a particular direction, with junctions, intersections, interchanges, traffic signals, or signs. Traffic may be separated into classes: vehicular; non-vehicular (e.g. bicycles); and pedestrian. Different classes may share speed limits and easement, or may be segregated. Some countries may have very detailed and complex traffic laws while others rely on drivers’ common sense and willingness to cooperate.

Organization typically reduces travel time. Though vehicles wait at some intersections, wait time at others is much shorter. An unexpected occurrence may cause traffic to degenerate into a disorganized mess: road construction, accidents, or debris may all disrupt the flow. 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.

Unorganized traffic

Unorganized traffic occurs in the absence of lanes and signals. Roads do not have lanes, though drivers tend to keep to the appropriate side if the road is wide enough. Drivers frequently overtake other drivers, and obstructions are not uncommon.

Intersections have no signals or signage, and a particular road at a busy intersection may be dominant (that is, its traffic flows) until a break in traffic, at which time the dominance shifts to the other road where vehicles are queued. At the intersection of two perpendicular roads, a traffic jam results if four vehicles face each other side-on.

Traffic pre-emption

In some areas, emergency responders are provided with specialized equipment which allows emergency response vehicles, particularly fire fighting apparatus, to have high-priority travel, by changing the lights in their corridor to green and intersecting streets along the corridor to red. The technology behind these methods have evolved, from panels at the fire department that could trigger and control green lights for certain major corridors, to optical systems, which the individual fire apparatus can be equipped with to communicate directly with receivers on the signal head.

Intelligent Transportation Systems

Intelligent Transportation Systems (ITS) is a system of hardware, software and operators that allow better monitoring and control of traffic in order to optimize traffic flow. As the number of vehicle lane miles traveled per year continues to increase dramatically, and as the number of vehicle lane miles constructed per year has not been keeping pace, this has led to ever-increasing traffic congestion. As a cost-effective solution toward optimizing traffic, ITS presents a number of technologies to reduce congestion by monitoring traffic flows through the use of sensors and live cameras, and in turn rerouting traffic as needed through the use of variable message boards (VMS), highway advisory radio (HAR) and other systems. Additionally, the roadway network has been increasingly fitted with additional communications and control infrastructure to allow traffic operations personnel to monitor weather conditions, for dispatching maintenance crews to perform snow or ice removal, as well as intelligent systems such as automated bridge de-icing systems which help to prevent accidents.

Image http://en.wikipedia.org/wiki/File:I-80_Eastshore_Fwy.jpg

This article is licensed under the GNU Free Documentation License. It uses material from the Wikipedia.