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Managing Time, Space, and Visibility
Characteristics/Visual Fields
Peripheral Vision
Fringe Vision
Peripheral Vision
Motion and Color Changes
Fringe Vision Referencing, Path of
Travel, Sightlines
Central Vision
Visual Lead, Targeting,
Signs, Signals
Central Vision
Factors Affecting Field of Vision
Normal 190°-200°
30 MPH 142°- 160°
45 MPH 100° - 90°
60 MPH 10° - 20°
PRINCIPLES OF VISUAL PERCEPTION
FINAL FILES ARE THE RESULT OF
YEARS OF SCIENTIFIC STUDY COMBINED
WITH THE EXPERIENCE OF YEARS
Basic Requirements for Driving
Driver Requirements
Visibility … Space X Time = Speed … Traction
Vehicle Requirements
An average driver makes 50 to 60 decisions per mile traveled …...
… most such decisions relate to visibility, space, time, and placement …. … all must be accomplished
within the range of available traction!
Judgmental Abilities Required To
Manage Time/Space Adequately• Space Relationships
• Speed Estimates
• Evaluation of Roadway
• Prediction of Others’ Actions
Space Management System• Search for objects or conditions• Evaluate the planned travel path ahead(visibility, traction, space, traffic
flow, topography, legal requirements)• Identify alternate paths of travel(look for an out)• Prepare to make adjustments in speed and/or position(learn to read the
route -it’s the smooth move - safer & economical)
RearviewMirror
SideMirrow
3 - 4 sec Following Distance
Fringe Vision
CentralVision
3 - 4 sec Following Distance
SideMirror
4 - 8 sec Stop Zone
12 - 15 sec VCZ
20 -30 sec VSA
• 20 – 30 sec search (VSA)• 12 – 15 sec path of travel (VCZ)• 4 – 8 sec immediate path (Stop Zone)• 3 - 4 sec following distance• Mirrors (rear interval) [10x minute] • Head checks [ any lateral movement]• Speedometer [1x a minute]
Visual Habits
20 sec VSA at:
35 mph = 1022 ft (0.2 mile)
55 mph = 1773 ft (0.3 mile)
65 mph = 1898 ft (0.4 mile)
Visual Process• Search roadway & off road areas 20 - 30 secs
ahead to plan path of travel• Identify conditions 12 - 15 secs ahead that could
interfere with path of travel• Predict conditions on/near road that could
increase risk• Decide at least 4 - 5 seconds ahead what actions
to take to reduce risk• Execute decisions
Visual Process: Following Distance
• Continually monitor the 3-to-4 second following distance
• Adjust as required by– Atmospheric conditions– Roadway and off-road surface and condition– Traffic conditions– Visibility– Following traffic
Visual Process: Mirror Use• Proper adjustment required• Monitor traffic to sides and rear while traveling and
stopping• Not for detail(objects in side mirror closer than they
appear)• Are vehicles present?• Where?• Size?• Speed?
• Mirror blind areas(head check)
Driving Process
• Search• Identify• Predict • Decide• Execute
SIPDE
Visual Search Categories
Roadway Features
Traffic Controls
Non-Motorized Users
Motor Vehicles
Aggressive Visual Search
Aim highGet the big pictureKeep your eyes movingLook for an out
Aggressive Visual SearchAn aggressive visual search involves:• Searching 20-30 seconds ahead• Identifying an alternate path• Identifying other highway users• Assessing the consequences of alternate
responses• Adjusting speed or position, and
communicating adjustment
Manage Risk By Adjusting Time/Space/Visibility
• Increase Vehicle Control• Increase Response Time
– increase space– adjust speed– increase visibility
A
B
REMEMBER YOU HAVE MORE TIME TO CORRECT A SITUATION AT A SLOWER SPEED AND IF YOU
ERR IT WILL BE LESS EXPENSIVE!
Manage Risk By Increase Distance From Hazard (Separating)
Vehicle on side of road
Pedestrian - vehicle conflict
Reduced traction,
vehicle, curve
Adjust Time/Space For the Least Harmful Result When Multiple Risks
Present (Compromising)Resolve possible responses into a single adjustment of speed and road position resulting in the least consequence for the greatest risk.
Three highway conditions that require speed adjustments are visibility, traction, and space.
How Fast is Too Fast?
It is not how quickly you can get there if everything goes well, but how quickly could you respond if something goes wrong?
Min/10mi
MPH Minsaved
24.1 2517.2 35 6.913.4 45 3.811.0 55 2.4
9.3 65 1.78.0 75 1.2
Time saved by going 10 mph faster for 10 miles
•Each 10 mph speed increase doubles chance of fatal injury if involved in a crash•10mph over speed limit is 3 point violation
IS IT WORTH IT TO SAVE 2 TO 7 MINUTES ?
utesS
d
tonds
fps
feet
utes min1.246046.125
52800
60secmin