Özet:

Basic traffic elements (flow, speed, density) are used in many stages of transportation process. Flow-speed-density relationship isan important concept, which translates traffic stream characteristicsinto mathematical or statistical rnodels. These models are widely usedin transportation engineering. The main objective of this research is finding out the nature of the relationships between the basic traffic elements characteristics for multi-lane highways in Baghdad city. Data has been collected throughout an extensive field survey on twenty selected sections in the study area. Photograph technique is usedto deterrnine the basic traffic elements. Statistical technique is applied analyze the collected data in order to present the best models to describe flow-speed-density relationships. The results of this study indicate that the linear relationship between speed and density is signification with confidence level (99%). The nature of this relation is considered during theformulation of the other relation-ships between traffic elements.

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