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Tuesday, March 1, 2016

How to field determination of saturation flow of Traffic

To know traffic flow,  two people are needed to carry out this study, one person needs to have a stop watch or a timer equipped device, and other to record a events with a appropriate software or a notebook computer. details such as area type, width, and grade of the lane being evaluated to be measured and recorded.

thak you need to have a good point for observation with a clear vision without any obstetrical and able to see traffic light, mark a specific point for traffic to enter, than follow below steps:
1. Timer starts the stop watch as green light and record the time
2. recorder immediately notes the last vehicle in the stopped queue and describes the timer and also notes vehicles details such as heavy and light and who turns right and left
3. timer than reads all the vehicles passing
4. timer records all the vehicles that passed and noted
5. width of the lane and slope of approach are then measured and recorded together with any unudal occurrence that might have effected the flow
6. just after the green phase is less than saturation flow, the time considered for calculating the saturation flow is theat between the time the rear axle of the car crosses the reference point t4 and the time the rear axle of the fourth car crosses the reference point tn. below equation can be used

Saturation flow = 3600/((t4-tn)/(n-4))

where n is the number of last vehicle surveyed.

field sheet for direct observation of prevailing saturation flow ratio



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