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Learning Objectives

Learning Objectives. To define and apply basic measures of traffic flow, including; Speed Volume Density Spacing and Headway Lane occupancy Clearance and gap. Traffic Flow. Complex: between vehicles and drivers, among vehicles

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Learning Objectives

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

  2. 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

  3. Speed (v) • Rate of motion • Individual speed • Average speed • Time mean speed Arithmetic mean • Space mean speed Harmonic mean

  4. Individual Speed (1) Spot Speed

  5. Time Mean Speed Mile post Observation Period

  6. Space Mean Speed Observation Distance Observation Period

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

  8. Volume (q)

  9. 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)

  10. Density (k)

  11. Density (k)

  12. Spacing (s) • Front bumper to front bumper distance between successive vehicles S2-3 S1-2

  13. Headway (h) • Time between successive vehicles passing a fixed point T=3sec T=0 sec h1-2=3sec

  14. Spacing and Headway spacing headway

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

  16. Spacing and Headway What are the individual headways and the average headway measured at location A during the 25 sec period? A h1-2 h2-3

  17. Lane Occupancy • Ratio of roadway occupied by vehicles L3 L2 L1 D

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

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