Highway design distances_rev09

Highway design distances_rev09 - Introduction to...

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Virginia Tech 1 Introduction to Transportation Engineering Discussion of Stopping and Passing Distances Dr. Antonio A. Trani Professor of Civil and Environmental Engineering Virginia Polytechnic Institute and State University Blacksburg, Virginia Fall, Spring 2009
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Virginia Tech 2 Introductory Remarks • The presentation of the materials that follow are taken from the American Association of State and Highway Officials (AASHTO): • “A Policy on Geometric Design of Highways and Streets - 2004” • This text is the standard material used by transportation engineering to design highways and streets
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Virginia Tech 3 Driver Performance • The human-machine system • The driver • Perception and reaction • Vehicle kinematic equations • Acceleration and deceleration problems • Stopping distance criteria • Passing sight distance criteria • Examples
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Virginia Tech 4 Human Machine Systems • Complex human-machine behavior in transportation engineering • Some examples: • Air traffic controllers interacting with pilots who in turn control aircraft • Highway drivers maneuvering at high speeds in moderate congestion and bad weather • A train engineer following train control signals at a busy train depot
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Virginia Tech 5 Sample Problem • Driving behavioral models are perhaps the easiest to understand Driver Strategy: control, guidance, and navigation
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Virginia Tech 6 The Driver • Transportation engineers deal with large numbers of drivers Elderly Middle age Young Handicapped, etc. • Design standards cannot be predicated on the basis of the “average driver” • In-class discussion • Example of reaction time study
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Virginia Tech 7 Anecdotal Experience About Drivers • Drivers do not like more than 0.3 g of lateral acceleration at low speeds (< 30 m.p.h.) • No more than 0.1 g at 60 m.p.h. • Human factor issues in highway design: a) As speed increases so does visual concentration b) As speed increases, the focus of visual concentration changes (600 ft. at 25 m.p.h., 2000 ft. at 65 m.p.h.) c) As speed increases, peripheral vision is reduced (100 deg. At 25 m.p.h., 40 at 60 m.p.h.) d) As speed increases, foreground details fade (large shapes meaningful at high speeds) e) As speed increases, space perception is impaired
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Virginia Tech 8 Visual Acuity • Ability to distinguish details clearly • Varies from person to person • Affected by the speed of the objects passing by • Affected by weather and environmental conditions (i.e., day acuity is better than nighttime acuity) • A person with 20/20 vision can read letters one inch in height at 60 ft. (or 1/3 inch at 20 ft.) • A person with 20/40 vision can read the same one inch letters at only 30 ft.
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This note was uploaded on 12/31/2011 for the course CEE 3604 taught by Professor Katz during the Fall '08 term at Virginia Tech.

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Highway design distances_rev09 - Introduction to...

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