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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.

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Presentation on theme: "Learning Objectives To define and apply basic measures of traffic flow, including; –Speed –Volume –Density –Spacing and Headway –Lane occupancy –Clearance."— Presentation transcript:

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 Period Observation Distance

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

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

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

14 Spacing and Headway spacing headway

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

16 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

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

18 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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