Design Driver

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Design Driver

• CE 453 Lecture 7

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Design Driver Characteristics

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

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Design Driver Characteristics Cont.

• Physical characteristics
• Processing ability
• Tolerable Accelerations/Decelerations
• Longitudinal (along roadway )
• Lateral (around curves)
• Vertical (comfort)

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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

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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

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• Picture this A little old lady who is used to
  her 5,000-lb. Buick Station Wagon is tonight
  poking along in her grandson's brand new Honda
  Civic Si - in the rain - on an unfamiliar road
  after spending four hours drinking Mojitos 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 Dads 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.

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Visual Acuity
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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

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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

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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
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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, especially
  for older drivers

Need to provide light transitions
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Visual Reception

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

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From GBSome 75-year old drivers require how
many times the more brightness at night to
receive visual information than a 25-year old
driver?
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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
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Hearing

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

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Perception/Reaction Time
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Perception-Reaction Process

• Perception
• Identification
• Emotion
• Reaction (volition)

PIEV Used for Signal Design and Braking Distance
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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

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

• Environment
• Urban vs. Rural
• Night vs. Day
• Wet vs. Dry
• Age
• Physical Condition
• Fatigue
• Drugs/Alcohol
• Distractions

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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)

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Age

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

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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_at_harristechnical.com
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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_at_harristechnical.com
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From Driver Characteristics and Impairment at
Various BACs H. Moskowitz, M. Burns, D.
Fiorentino, A. Smiley, P. Zador
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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?)

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Weather

• Fog
• Rain
• Ice
• Snow

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Understanding
Flashing DONT WALK
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Understanding
Count down signal
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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, dont
  understand meaning of left turn displays

Human Factors - Perception and Reaction by Joseph
E. Badger. jebadger_at_harristechnical.com
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Fatigue

• Increases perception/reaction time
• Study by American Automobile Association found
  that in 221 truck accidents 81.6 of the drivers
  had been driving nine or more hours.
• 41 of truck accidents

Human Factors - Perception and Reaction by Joseph
E. Badger. jebadger_at_harristechnical.com
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• Dp 1.47(V)(t)
• where
• Dp Distance traveled during PIEV process
  (feet)
• V velocity (mph)
• t perception-reaction time 2.5s

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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!
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Perception/Reaction Applications

• Stopping sight distance
• Passing sight distance
• Placement of signs/traffic control devices
• Design of horizontal/vertical curves

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Driver Expectancy
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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

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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.

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Driver Expectancy

• Reduce load on driver
• Simplify driving task
• Keep roadway environment within expected
  parameter
• Traffic control
• Consistent size, color, shape
• Design features depends on functional class
• On freeways we expect 12-foot lanes
• Can this foster complacency???

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Selection of Design Driver
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Design criteria must be based on the capabilities
and limitations of most drivers and pedestrians
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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)
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 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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Driver Activities in Selection of Path

• Control (overt actions)
• Road Edge
• Avoid a Car
• Guidance (decisions)
• Lane Placement
• Car Following
• Passing

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Driver Activities in Selection of Path Cont.

• Navigation Level (planning)
• Maps
• Observe a directional sign

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Pedestrians

• Characteristics similar to driver
• Design of pedestrian facilities
• Signal timing get peds across during red phase

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Pedestrians

• Walking Speed varies between 3 to 8 ft/sec
• Design value is 4 ft/sec

Used to calculate safe pedestrians crossing time
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Bicycles

• On-road
• Separate facilities
• Similar to driver (perception-reaction)
• Divided by AASHTO into 3 classes
• Class A experienced or advanced bicyclists
• Consider bike as a vehicle and ride comfortably
  with traffic
• Usually not allowed on freeways
• Class B less experienced bicyclists
• Usually prefer neighborhood streets and bike
  facilities
• Class C children on their own or with parents
• Mainly residential