Cal Poly Pomona CE 222 - Notes for Chapter 6 Traffic Characteristics (3 pages)

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Notes for Chapter 6 Traffic Characteristics



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Notes for Chapter 6 Traffic Characteristics

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Lecture Notes


Pages:
3
School:
California State Polytechnic University, Pomona
Course:
Ce 222 - Highway Engineering

Unformatted text preview:

CE222 Highway Engineering Notes for Chapter 6 Traffic Characteristics 1 Traffic Flow Characteristics Traffic on a roadway is considered as a flow just like water flowing in a pipeline or a river This assumption is not accurate but realistic in highway engineering An understanding of traffic flow characteristics is very important for highway design Parameters measuring traffic flow Traffic Speed Travel Time Volume Density and Capacity 1 Traffic Speed and travel time Keep in mind the speed and travel time here are related to traffic FLOW Speed Spot speed Instantaneous speed of a vehicle MPH or KM H Measuring equipment laser gun Time mean speed Equation 6 1 on page 132 Space mean speed Equation 6 2 on page 132 Relation between time mean speed and space mean speed See Equation 6 3 Spot speed is related to an individual vehicle in the traffic flow Time Mean speed and space mean speed are measures obtained from a sampling set of vehicles in the traffic flow Overall speed A measure of traffic flow on a relatively long section of street or highway between an origin and destination Testing vehicle represents traffic flow floating in the traffic flow no passing over other vehicles and no being passed by other vehicles Total distance total time including traffic delay Running speed A measure similar to overall speed Total distance running time 2 Traffic Volume and rate of Flow Traffic Volume of vehicles passing a point along a roadway or traffic lane per unit of time ADT average daily traffic volume of vehicles passing a point on a roadway during a period of 24 consecutive hours averaged over a period of 365 days DHV design hourly volume It is a measurement to indicate the demand or intensity of the facility 30th highest hourly volume of the design year Why 30th Rate of Flow See Page 135 Very important concept Peak Hour Factor ratio of total hourly volume to the maximum rate of flow within a hour 3 Traffic Density or traffic concentration Average number of vehicles occupying a



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