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Published byHalle Silvers Modified about 1 year ago

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Learning Objectives To define and apply basic measures of traffic flow, including; –Speed –Volume –Density –Spacing and Headway –Lane occupancy –Clearance and gap

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Traffic Flow Complex: between vehicles and drivers, among vehicles Stochastic: variability in outcome, cannot predict with certainty Theories and models –Macroscopic: aggregate, steady state –Microscopic: disaggregate, dynamics –Human factor: driver behavior

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Speed (v) Rate of motion Individual speed Average speed –Time mean speed Arithmetic mean –Space mean speed Harmonic mean

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Individual Speed (1) Spot Speed

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Time Mean Speed Mile post Observation Period

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Space Mean Speed Observation Period Observation Distance

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Volume (q) Number of vehicles passing a point during a given time interval Typically quantified by Rate of Flow (vehicles per hour)

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Volume (q)

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Density (k) Number of vehicles occupying a given length of roadway Typically measured as vehicles per mile (vpm), or vehicles per mile per lane (vpmpl)

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Density (k)

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Spacing (s) Front bumper to front bumper distance between successive vehicles S 1-2 S 2-3

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T=3sec Headway (h) Time between successive vehicles passing a fixed point T=0 sec h 1-2 =3sec

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Spacing and Headway spacing headway

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Spacing and Headway A What are the individual headways and the average headway measured at location A during the 25 sec period?

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Spacing and Headway A What are the individual headways and the average headway measured at location A during the 25 sec period? h 1-2 h 2-3

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Lane Occupancy Ratio of roadway occupied by vehicles L1L1 L2L2 L3L3 D

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Clearance (c) and Gap (g) Front bumper to back bumper distance and time Spacing (ft) or headway (sec) Clearance (ft) or Gap (sec)

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