Lecture 15

Lecture 15 - The Pennsylvania State University Department...

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Unformatted text preview: The Pennsylvania State University Department of Civil and Environmental Engineering Lecture 15: Traffic Stream Parameters CE 321: Highway Engineering Fall 2007 Purpose of Traffic Analysis Primary purpose / function of a highway is safety and mobility. Traffic analysis is means of measuring vehicle performance. – Vehicles per unit time. – Vehicle types. – Vehicle speeds. – Variation in traffic flow over time. Influences number of lanes, pavement types, geometric design, traffic control devices. Congestion in America will Continue to Get Worse and Worse WHY ? Visit Any Urban/Suburban Area and Try To Drive From One Side of Town To The Other ! Photo Courtesy of Acclaim Images Automobile is America Primary Mode of Transportation Allowed Life Activity Sprawl Totally Dependent on Auto / Trucks Congestion Traffic Continues to Grow Uncontrolled Development Development on Local Roadways How Many Vehicles Can Travel On An Expressway Lane/ Hour ? Capacity Seconds / Hour = 3600 Headway (Vehicle spacing) – Human factor Capacity Is: 2,400 Vehicles/Hr/Lane Traffic Stream Parameters Uninterrupted flow – Free from influence of traffic control devices – Examples: freeways, multi-lane highways, and two-lane highways Interrupted flow – Influenced by signals, stop signs Traffic Parameters Macrscopic parameters – Flow (vehicles / hour): q – Speed (miles / hour): u – Density (vehicles / mile): k Microscopic parameters – Spacing—distance between successive vehicles, front bumper to front bumper (ft/veh) – Headway—the time between successive vehicles, front bumper to front bumper (sec/veh) Flow the number of vehicles that pass a point during a specified period of time (also known as rate of flow or sometimes volume although volume and flow are really different; volume is a one hour flow rate)....
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This note was uploaded on 04/11/2008 for the course C E 321 taught by Professor Pietrucha,martinkeller,michaelwi during the Spring '07 term at Penn State.

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Lecture 15 - The Pennsylvania State University Department...

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