Microsoft Word - Traffic Characteristics

Microsoft Word - Traffic Characteristics - Total PHF ×...

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1 Fundamentals of Traffic Flow and Analysis Traffic Characteristics: Speed (u) - Time Mean Speed (Spot Speed) n u u i t = - The i th Percentile Speed The value of speed below which i percent of the vehicles travel - Median Speed 50 th percentile speed - Modal Speed The value of speed that occurs most frequently - Pace Range of speed for 10 mph intervals - Space Mean Speed = = n 1 i i s t nd u or = ) u 1 ( n u i s Where, d = Length of roadway section t i = Time for the i th vehicle to travel distance d. t i = d/v i - Overall Speed (Travel Speed) Time Travel Total Distance Total u = - Running Speed Time Running Distance Total u = Running Time = Travel Time – Delay Time
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2 Volume (q) The number of vehicles that pass a point along a roadway or traffic lane per unit of time. e.g. vph, vpd, vpy t n q = - Average Annual Daily Traffic (AADT) 360 counts) hour (24 AADT 360 1 i = = - Average Daily Traffic (ADT) n counts) hour (24 ADT n 1 i = = 1< n <360 - Design Hourly Volume (DHV) 30 th highest hourly volume, (ADT) k% DHV = k ≈ 16% - Peak Hour Factor (PHF) rate flow minute 15 Peak 4 Volume hourly
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Unformatted text preview: Total PHF × =-Peak Hour Volume (PHV) PHF Count Volume Total PHV = 3 • Density (k) Number of vehicles that occupy a unit length of roadway at a given instant, (veh/mile-lane) l n k = • Headways -Time Headway (h t ) Time between successive vehicle passages (sec) q 3600 h t =-Space Headway (h sp ) The distance between successive vehicle passages (ft) k 5280 h sp = • Gaps -Time Gap (sec) 5280 3600 u l q 3600 g t ×-=-Space Gap (ft) l k 5280 l h g sp sp-=-= 4 • Basic Relationship Between Traffic Volume (q), Speed (u), and Density (k): q = k.u (vphpl) = (veh/mile-lane)(mile/hr) ) u u (1 k k ) k k (1 u u f j j f-=-= 2 u u u q ) u u (u k q ) u u (1 uk q f m f 2 j f j = ⇒ = ∂ ∂-=-= 4 u k q f j m = ∴ Where, u f = Free speed k j = Jam density k m & u m = k & u values corresponding to q m q m u f u m u f u m q m k m k j k m k j 2 k k k q ) k k (k u q ) k k (1 ku q j m j 2 f j f = ⇒ = ∂ ∂-=-=...
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This note was uploaded on 02/09/2011 for the course ECON 2250 taught by Professor Schultz during the Spring '11 term at UNO.

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Microsoft Word - Traffic Characteristics - Total PHF ×...

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