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