Transcript Vision Notes - Garnet Valley School District

Vision & Driving
90% of your decisions are based on
information you gather with your eyes
Peripheral Vision=To the sides
Central Vision=In the front
Vertical Vision= Up & Down
Focus Vision=Targeting
Visual Fields in Operation
Vision Characteristics
Focus Vision
Focus Vision (Focal/Foveal)
Central Vision
Visual Lead, Targeting, Signs,
Signals
Central Vision (Limited
Fringe Area)
Referencing, Path of
Travel, Sightlines
Peripheral Vision
Motion and Color
Changes
Peripheral Vision
Driver’s Useful Vision Areas
Gathering Useful Visual Information
Focus Vision Area (Focal)
3 to 5 degrees of useful information
 Targeting Skills
 Establishing Visual Lead
 Reading Signs and Interpreting Signals
Driver’s Useful Vision Areas
Gathering Useful Visual Information
Central Vision Area (Inner Fringe)
30 to 36 degrees of useful information
 Vehicle to Roadway Reference
 Viewing Path of Travel
 Viewing Line of Sight to Target Area
Driver’s Useful Vision Areas
Gathering Useful Visual Information
Peripheral Vision (Outer Fringe)
175 to 185 degrees of useful information
 Motion Changes
 Color Changes
Visual Fields in Operation
Standard Visual Reference for
Lane Position 1
Target
Path of Travel
When focus vision is on the target at the end of the
path of travel, the central or inner fringe vision will
allow the driver to see the placement of vehicle in
the roadway...
Effect on
Vision
Speed
As you go faster:

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
central vision decreases and blurs
peripheral vision decreases
sudden changes in steering may cause
exaggerated vehicle movements
VISION FIELDS
NARROW
Vision Sightlines/Travel Paths
Line of Sight Limitations or Restrictions
When line of sight is
restricted or blocked,
a speed adjustment is
needed until visual
lead, target area, and
the line of sight are
restored...
Speed and Effect on Vision
Looking farther away from your vehicle lengthens or
increases line of sight (LOS) and path of travel (POT)
areas which:
 allows more time to get information;
 increases peripheral vision field, giving time
for adequate response; and
 places more space between other users and
your vehicle, so sudden steering changes are
held to a minimum.
Determining Following Intervals
Fixed Object or Shadow
One Thousand One
One Thousand Two
One Thousand Three
One Thousand Four
Time, Speed, and Distance
Relationships on Dry, Clean Surfaces
Following Interval
2 Sec. 3 Sec.
4 Sec.
1/2 sec 3/4 sec Total
Steer Brake Brake
Dist.
Dist.
Dist.
Vehicle
Speed
Ft./Sec.
Travel
30 mph
44 f/s
88 ft.
132 ft.
176 ft.
22 ft.
33 ft.
80 ft.
40 mph
58 f/s
116 ft.
174 ft.
232 ft.
29 ft.
44 ft.
125 ft.
50 mph
74 f/s
148 ft.
222 ft.
296 ft.
37 ft.
56 ft.
190 ft.
60 mph
88 f/s
176 ft.
264 ft.
352 ft.
44 ft.
66 ft.
275 ft.
70 mph
104 f/s
208 ft.
312 ft.
416 ft.
52 ft.
78 ft.
385 ft.
Following Intervals
 2 Seconds… Permits driver time to steer out of problem areas at
all listed speeds on a dry surface and braking out of problems at
speeds under 35 mph.
 3 Seconds… Permits driver time to steer out of problem areas at
all listed speeds on dry surface and braking out of problems at
speeds to 45 mph.
 4 Seconds… Permits driver to steer out of problems at all listed
speeds on dry surface and braking out of problems at speeds to
legal limit of 65 mph.
*
Factory equipped passenger car tires may not be designed to steer out of
problem areas at speeds beyond 75 mph. Speed rated tires are required due
to sidewall flexion problems at higher speeds and turning movements.
Importance of Good Vision
Distance Vision-Ability to see far down the road 20-30 seconds
Depth Perception
 Helps you control your following distance and lets you adjust
your position in traffic, change lanes, pass, pull into traffic
 To compensate for poor depth perception-Increase following
distance
Color Vision
 Drivers must recognize colors in objects (signs, signals, etc.)
 Can color Bind people drive ? (Shape, Shade, or position)
Vision Problems
Contrast Sensitivity- Helps you see details in the driving environment
Night Vision

Good night vision requires an ability to see in low and variable light
conditions

Reduced visibility at night due to dirty windshield, headlights, rain,
etc.
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Glare Vision- Ability to see when there is rapid increase in light
 Headlights
 Sun
 Snow
 Rain
Glare Recovery- Caused by the sudden brightness of oncoming
headlights
 1.Do not look directly into headlights
 Reduce speed
 Be aware on hills and curves
Assessment
1. What are the 4 types of Vision? List and Explain.
2. If your focus vision is on the target at the end of the path of travel,
which vision will allow the driver to see the placement of vehicle in the
roadway.
3. What three things will occur when you increase your speed?
4. Increased line of sight and path of travel will lead to what three
things to occur?
5.Explain following distance.
6.What is considered a safe following distance?
7. At what speed (s) do you still have time to steer out of problems if
you are following at 2 seconds?
8. What is the three factors for having good vision?
9. How do color blind drivers determine the color of traffic lights?
10. What is Glare Recovery, and how can a driver compensate for this
problem?
11. What are the ways items we can identify to help us determine that
we have control of our risk?
12. What are the three zones that involve time and space, and are
important to our path of travel?