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Design Driver

Design Driver. CE 453 Lecture 7. Design Driver Characteristics. Design Driver: driver most expected to use facility (familiar or unfamiliar?) Accommodated in design, signing, etc. Design Driver Characteristics Cont. Physical characteristics Processing ability

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Design Driver

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  1. Design Driver CE 453 Lecture 7

  2. Design Driver Characteristics • Design Driver: driver most expected to use facility (familiar or unfamiliar?) • Accommodated in design, signing, etc.

  3. Design Driver Characteristics Cont. • Physical characteristics • Processing ability • Tolerable Accelerations/Decelerations • Longitudinal (along roadway ) • Lateral (around curves) • Vertical (comfort)

  4. Design Driver Characteristics Cont. • Others?: age, gender, physical condition (alcohol, etc.), mental capabilities, skill (self perception – are you in the top ½ of driver skill?) • Two others related to design: perception-reaction time and expectancy

  5. Design Driver • Wide range of system users • What range of drivers use the system? • Ages: 16 year old to 80 year old • Different mental and physical states • Physical (sight, hearing, etc) • experience • Design Driver: driver most expected to use facility

  6. Picture this: A little old lady who is used to her 5,000-lb. 1971 Buick LeSabre Centurion Estate Station Wagon is tonight poking along in her grandson's brand new Suzuki Samurai - in the rain - on an unfamiliar road after spending four hours drinking fuzzy navels at her 50th class reunion at Neil Cosgrove's Friendly Bar & Grill. Compare her to the 13-year-old who swiped Dad's keys and is now piloting Dad’s Porsche at Mach II down the same stretch of unfamiliar road. These two unlikely individuals inadvertently attempt to occupy the same space simultaneously. Yet you certainly can't apply the same perception and reaction times to both drivers.

  7. Visual Acuity

  8. Visual Reception • Visual Acuity: Ability to see fine details • Static (stationary objects): • Depends on brightness • Increases with increasing brightness up to ~ 3 candles (cd/sq ft) -- remains constant after that • Contrast • Time (0.5 to 1.0 second) • Dynamic (ability to detect moving objects) • Clear vision within a conical angle 3 to 5º • Fairly clear within 10 to 12º • Key criteria in determining placement of traffic signs

  9. Visual Reception • Peripheral Vision: Ability to see objects beyond the cone of clearest vision (160 degrees) • Age dependent • Objects seen but details and color are not clear

  10. Visual Reception • Color Vision: Ability to differentiate one color from another • Lack of ability = color blindness • Combinations to which the eye is the most sensitive • Black and white • Black and yellow Key in determining traffic signs colors

  11. Visual Reception • Glare Recovery: Ability to recover from the effects of glare • Dark to light : 3 seconds -- headlights in the eye • Light to dark: 6 seconds – turning lights off • Usually a concern for night driving Need to provide light transitions

  12. Visual Reception • Depth perception • Ability to estimate speed and distance • Passing on two-lane roads • Signs are standardized to aid in perceiving distance

  13. From GB:Some 75-year old drivers require how many times the more brightness at night to receive visual information than a 25-year old driver?

  14. Some 75-year old drivers require how many times more brightness at night (to receive the same visual information) than a 25-year old driver?32 timesneed 2x brightness for each decade past 25

  15. Hearing • Hearing perception • Ability to detect warning sounds • Sirens, horns

  16. Perception/Reaction Time

  17. Perception-Reaction Process • Perception • Identification • Emotion • Reaction (volition) PIEV Used for Signal Design and Braking Distance

  18. Perception-Reaction Process • Perception • Sees or hears situation (sees deer) • Identification • Identify situation (realizes deer is in road) • Emotion • Decides on course of action (swerve, stop, change lanes, etc) • Reaction (volition) • Acts (time to start events in motion but not actually do action) • Foot begins to hit brake, not actual deceleration

  19. Typical Perception-Reaction time range is: 0.5 to 7 seconds Affected by a number of factors. What are they?

  20. Perception-Reaction Time Factors • Environment: • Urban vs. Rural • Night vs. Day • Wet vs. Dry • Age • Physical Condition: • Fatigue • Drugs/Alcohol • Distractions

  21. Perception-Reaction Time Factors • medical condition • visual acuity • ability to see (lighting conditions, presence of fog, snow, etc) • complexity of situation (more complex = more time) • complexity of necessary response • expected versus unexpected situation (traffic light turning red vs. dog darting into road)

  22. Perception Reaction Time (PRT) • Time from Perception to Initial Reaction to Stimulus (Example)

  23. Age • Older drivers • May perceive something as a hazard but not act quickly enough • More difficulty seeing, hearing, reacting • Drive slower

  24. Age • Younger drivers • May be able to act quickly but not have experience to recognize things as a hazard or be able to decide what to do • Drive faster • Are unfamiliar with driving experience • Are less apt to drive safely after a few drinks • Are easily distracted by conversation and others inside the vehicle • May be more likely to operate faulty equipment • Poorly developed risk perception • Feel invincible, the "Superman Syndrome” Human Factors - Perception and Reaction by Joseph E. Badger. jebadger@harristechnical.com

  25. Alcohol • Affects each person differently • Slows reaction time • Increases risk taking • Dulls judgment • Slows decision-making • Presents peripheral vision difficulties Human Factors - Perception and Reaction by Joseph E. Badger. jebadger@harristechnical.com

  26. From: Driver Characteristics and Impairment at Various BACs H. Moskowitz, M. Burns, D. Fiorentino, A. Smiley, P. Zador

  27. Experience • Even NASCAR drivers practice Familiarity • Faster on familiar • Unfamiliar more distracted • Rental car on unfamiliar road at 10 pm when it starts to rain (What is the driver doing?)

  28. Weather • Fog • Rain • Ice • Snow • affects ability to see (snow, fog) • changes ability to stop (ice, snow, wet)

  29. Understanding Flashing DON’T WALK

  30. Understanding Count down signal

  31. Understanding • Most people do not reduce speed in a work zone until they actually see activity • Only 78% of drivers in a study understood what “Lane Ends” mean • Many people, especially older drivers, don’t understand meaning of left turn displays Human Factors - Perception and Reaction by Joseph E. Badger. jebadger@harristechnical.com

  32. Fatigue • Increases perception/reaction time • Study by American Automobile Association found that in 221 truck accidents only 18.4% of the drivers had been driving less than nine hours. • 41% of truck accidents Human Factors - Perception and Reaction by Joseph E. Badger. jebadger@harristechnical.com

  33. Dp = 1.47(V)(t) where: Dp = Distance traveled during PIEV process (feet) V = velocity (mph) t = perception-reaction time = 2.5s

  34. Example How much longer does it take an impaired driver to perceive/react than an unimpaired one at 65 mph? Unimpaired has P/R time of 2.5 seconds Dp = 1.47(V)(t) = 1.47(65 mph)(2.5 sec.) ~ 240 feet Impaired Driver has P/R time of 4 seconds Dp = 1.47(65 mph)(4 sec) ~ 380 feet Difference is 380 – 240 = 140 feet Difference is safety and economic problem!

  35. Perception/Reaction Applications • Stopping sight distance • Passing sight distance • Placement of signs/traffic control devices • Design of horizontal/vertical curves

  36. Driver Expectancy

  37. Driver Expectancy • Expectancy (def) – an inclination based on previous experience to respond in a set manner to a roadway, traffic, or information situation • Types • A Priori – long-term (based on collective past experience) PRT = 0.6s avg., some 2.0s • Ad Hoc – short-term (based on site-specific practices/situations encountered during a particular trip on a particular roadway, PRT = 1.0s avg., some 2.7s Reaction time and car accident applet: http://www.phy.ntnu.edu.tw/java/carDistance/carAccident.html

  38. http://www.sdt.com.au/STOPPINGDISTANCE.htm

  39. Driver Expectancy • Driver Expectancies (what do we expect as drivers?) • Specific colors (red = stop) • Driver ahead not to decelerate rapidly • Slower drivers in right lane • Work zone signs = people working • Lane size • Etc.

  40. Driver Expectancy • Reduce load on driver • Simplify driving task • Try to keep roadway environment within “expected parameter” • Traffic control • Consistent size, color, shape • Design features – depends on functional class • Fwys expect 12 foot lanes • Can this foster complacency???

  41. Selection of Design Driver

  42. Design criteria must be based on the capabilities and limitations of most drivers and pedestrians

  43. The 85th percentile is generally used to select Design Criteria The 95th percentile or higher is used where the consequences of failure are severe AASHTO recommends 2.6 seconds for stopping sight distance (90th)

  44. Role of Transportation Engineer • allow proper sight distance in design, sign placement • avoid hitting driver with too much info at once • one sign at a time • clarity (sign size, color, reflectivity)

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