ENVIRONMENTAL DISTRACTION ON TRAFFIC CONTROL INFRASTRUCTURE CONSPICUITYJohannes BEZUIDENHOUT Prakash RANJITKAR Roger DUNN

Visual Memory

• Sensory memory = 1-2s• Working memory = < 15s then deterioration (6

objects)• Long term associative =

Visual ExpectancyTarget location (Martens, M.J. & Fox, M.R.J, 2007)

– Sign location wrong- • searched obvious location, then some delay in finding

expected sign– Sign not expected –

• large delay or missed– Differences in outcome:

• Experience or network knowledge• Expectation• Habit missing new or changed signs

Eye Tracker Set-up

Complexity of Driving Environment

Environmental Distractions

Typical Non-distracted

Hazard Distraction

Reflexive Socio-cognitive Distraction

Social Distraction

Consequences of Hazard/DistractionSlowed Response• Delayed reaction

+1.5s• Reflexive socio-

cognitive processing • Mental workload –

hysteresis effect

Change Detection• Vehicles more

difficult than signs• Visual/cognitive load

decreases peripheral vision

Red-light Running

8 sec

6 sec

4 sec

2 sec

Probability of Stopping

10% stop

90% stop

Dilemma Zone

Gaze Traces

Gaze Heatmap

Fixation

Dynamic Hazards

Dynamic Hazards

Dynamic Hazards

Distraction - Cyclist

Dynamic Distraction vs. Hazard

Cyclist&Car

Time to First Fixation from 112m• No distraction Karo 2 – 71% fixated• Took 1.81s on average• Distraction Karo 1 - 59% failed to fixate signal over

entire 8s• Remainder took 3.85s from 8s mark from approach• 2s difference in delayed reaction

Road AoI Mean(s)

Stdev Samplefixated

Significant difference @

5%

Willis Signals_L_R

5.24 3.23 71% KaroVicL2

KaroVicL1 Signals_L_R

3.85 2.77 41% -

KaroVicL2 Signals_L_R

1.81 1.53 71% Willis

8s Mean Pursuit Fixation TimeHa

zard

-Cyc

le

Sign

al L

_R

Sign

al L

_R

Car_

Foll.

Dist

ract

ion

Pl

Dist

ract

ion

Pr

Sign

al L

KaroVicL1 KaroVicL2 Willis

0.0000.2000.4000.6000.8001.0001.2001.4001.6001.800

Mea

n fix

atio

n du

rati

on(s

)

Missed Signal: Peer Proxy

Queue compression

Mean Pursuit Fixation Duration per 2s Segment

Haza

rd-C

ycle

Sign

al L

_R

Sign

al L

_R

Car_

Foll.

Dist

ract

ion

Pl

Dist

ract

ion

Pr

Sign

al L

KaroVicL1 KaroVicL2 Willis

0.000

0.100

0.200

0.300

0.400

0.500

Mea

n pu

rsui

t fix

atio

n ti

me

(s)

60% missed

30% missed

Discussion• Dynamic hazard – pedestrians, cyclists,

vulnerable road users, etc.• Distraction 30-60% miss signal• Pursuit fixation on signal over 8s = 490ms• Discharging queue commanded 1500ms• Cyclist commanded 1200ms• Do we need target fixation? • If not, how close?• Actual signal fixation minimum duration

unknown