Traffic Stream Characteristics

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Traffic Stream Characteristics
Traffic facilities are broadly separated into two principal categories. * Uninterrupted flow
* Interrupted flow
The major difference between the uninterrupted and interrupted flow facilities is the impact of time. On uninterrupted facilities, the physical facility is available to drivers and vehicles all at a time. On a given interrupted flow facility, the movement is periodically barred by “signal systems”. The signal timing, therefore, limits access to particular segments of the facility in time. The interrupted flow is more complex than the uninterrupted flow. Traffic Stream Parameters

Traffic stream parameters fall into two broad categories.
Microscopic parameters: describe traffic stream as a whole. Major macroscopic parameters are * Volume (rate of flow)
* Speed
* Density
Microscopic parameters: describe the behavior of individual vehicles within the traffic stream. Major microscopic parameters are * Speed of individual vehicles
* Headway
* Spacing
1. Flow or Volume (Q)
There are practically two ways of defining flow or volume on a road. One is defined as the number of vehicles that pass a point on a highway or a given lane or direction of a highway during a specific time interval. In second method the measurement is carried out by counting the number of vehicles, nt, passing a particular point in one lane in a defined time period T. The flow Q expressed in vehicles/hour is given by Q=ntT

Flow is expressed in planning and design field taking a day as the measurement of time. Volume, Demand and Capacity

In practical terms, volume is what is, demand is what motorists would like to be, and capacity is the physical limit of what is possible. Volume: would be the number of vehicles counted passing the study location in the hour. Demand: would be the volume plus the vehicles of motorists wishing to pass the site during the study hour who were prevented from doing so by congestion. The...
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