Human Characteristics in Road Transport

Human Characteristics

Road transport involves:

  • Human (driver, pedestrian)

  • Vehicle

  • Road/Highway

  • Environment (weather, time of day)

  • Independent interactions create a complex system.

Human Element

  • Driver characteristics vary in skills and abilities.

  • Affected by factors like fatigue and alcohol.

  • Use of average values (85th or 90th percentile).

Sensing

  • Drivers receive information through feeling, seeing, hearing, smelling.

  • Examples: temperature, forces, vibrations.

Feeling

  • Drivers experience forces like gravity and acceleration.

  • G-Force: acceleration relative to free-fall (9.81 m/s^2, 32.2 ft/s^2).

  • Kinesthesia: Sensation of bodily position.

  • Proprioceptors: provide feedback for driver action.

  • Vestibular: messages received through the vestibular nerve (inner ear) for direction, movement, and balance.

Seeing

  • Sight is most important sense in driving (90% of information).

  • Foveal vision: concentrated in a small area.

  • Peripheral vision: outside direct line of vision.

Visual Characteristics of the Eye

  • Visual Acuity

    • Ability to see fine details; static vs. dynamic.

    • Static Acuity: 0.50 - 1.0 sec

  • Peripheral Vision

    • Ability to see objects outside the center (120-180 degrees).

  • Color Vision

    • Ability to differentiate colors.

    • Compensate with shape, black/white or black/yellow colors.

  • Glare Vision and Recovery

    • Glare Vision: Seeing when subject to bright light

    • Glare Recovery: Time required to recover from glare effects (3-6 seconds).

  • Depth Perception

    • Ability to estimate speed and distance.

    • Important for head-on crashes.

Human Factors Applied to Highway Design

  • As speed increases:

    • Visual concentration increases.

    • The point of visual concentration recedes.

    • Peripheral vision diminishes.

    • Foreground details fade.

    • Space perception becomes impaired.

Perception-Reaction

  • Hearing and Smelling: Important for preventing collisions.

  • Perception: Extracting information from the environment.

  • Perception–Reaction Time (PRT): Time between stimulus and initial response.

  • PIEV

    • Perception: driver sees object

    • Identification: driver identifies object

    • Emotion: driver decides action

    • Volition: driver executes action

  • PRT is affected by age, fatigue, and environmental conditions.

  • AASHTO recommends 2.50 sec for stopping sight distance.

Perception and Reaction Time

  • Perception Delay: time between visibility and point of perception.

  • Apperception Interval: time to determine a potential hazard.

  • Reaction: analytical and decision-making.

  • Total reaction: reaction plus control response.

Driver Strategy

  • Driver Performance depends on:

    • Decision

    • Timing

    • Location/type of obstacle

    • Relative speed

    • Road characteristics