Examining visual behavior of drivers while using adaptive cruise control on

commercial motor vehiclesKevin Grove

Center for Truck & Bus Safety

Virginia Tech Transportation Institute

Adaptive Cruise Control (ACC)

�Automation technology that can control speed and headway on heavy vehicles � Radar mounted on front bumper tracks lead vehicle

� Included in heavy vehicle ADAS products such as OnGuardTM or Wingman®

� Newer generations include cameras with object detection for alerts, but not for ACC

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ACC Operation

�Driver selects a speed setting

�If slower lead vehicle present, ACC will reduce speed to maintain a safe headway

�If faster lead vehicle present or no lead vehicle present, maintains set speed

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How Do Drivers Use ACC?

�ACC allows driver to “follow” a lead vehicle with headway control

�As a low level automation technology, drivers should maintain full awareness

�In the real world, drivers attention may be different when using ACC

�Could impact ability to react in critical situations

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Data on ACC Usage

�As part of a NHTSA study VTTI collected naturalistic data from 150 trucks equipped with OnGuardTM or Wingman® AdvancedTM

products

�Video of driver’s face whenever truck in motion

�Possible to evaluate visual behaviors � With and without cruise control active

� During car following and non-car following

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VTTI’s Data Collection

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Location of

Meritor WABCO

OnGuardTM

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VTTI’s Data Collection

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WABCO

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Defining Car Following

�Defined “car following” based on radar data of lead vehicle� Car following with ACC if system controlled headway for at least 30 seconds

� Manual car following if driver keeps truck within 4.5 seconds headway for 30 seconds while distance oscillated

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Data Sampling and Analysis

�Sampled 3,000 thirty second windows across four conditions

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Following Lead

Vehicle

Not Following Lead

Vehicle

Cruise Control ActiveAdaptive Cruise Control

(1000)

Standard Cruise Control

(500)

Cruise Control

Inactive

Manual Car Following

(1000)

Manual Driving

(500)

Status of Lead Vehicle

Sta

tus

of

Cru

ise

Co

ntr

ol

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Visual Metrics

�Total eyes off road time (TEORT)� Within each 30 second window

�Average duration of off-road glances� With incomplete glances at the start or end of 30-second windows

removed

�Rate of off-road glances� With incomplete glances at the start or end of 30-second windows

removed

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One-factor Comparisons

�ACC vs. Standard cruise control

�Manual car following vs. Manual non-car following

�ACC vs. Manual car following

�Standard cruise control vs. Manual non-car following

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Two-factor Comparisons

�All cruise control usage vs. All manual driving� Combine ACC and standard cruise control

� Combine Manual car following and manual driving

�All car following vs. all non-car following� Combine ACC and manual car following

� Combine standard cruise control and manual driving

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Average TEORT

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6.1 6.75.3

6.1

0.0

5.0

10.0

15.0

20.0

25.0

30.0

ACC Standard Cruise

Control

Manual Car

Following

Manual Non-Car

Following

Tota

l D

ura

tion

Ey

es O

ff F

orw

ard

Road

way

(sec

on

ds)

Event Type

13

Average Glance Duration

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1.07 1.090.97 1.01

0.0

0.5

1.0

1.5

2.0

2.5

3.0

3.5

4.0

ACC Standard Cruise

Control

Manual Car

Following

Manual Non-Car

Following

Mea

n G

lan

ce D

ura

tion

(se

con

ds)

Event Type

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Average Rate of Off-road Glances

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1.81 2.001.74 1.91

0.0

1.0

2.0

3.0

4.0

5.0

6.0

7.0

8.0

ACC Standard Cruise

Control

Manual Car Following Manual Non-Car

Following

Off

-Road

Gla

nce

Rate

per

10 S

econ

ds

Event Type

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ACC vs. Manual Car Following

�While following vehicles drivers spent more time looking away from the road when using ACC

�The additional time was due to longer glances away from the road� No difference in rate of glances away from road

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ACC vs. Standard Cruise Control

�While ACC controlled headway drivers spend less time looking away from the road

�The additional time was due to more frequent glances away from the road� No difference in average glance duration off-road

�Have a lead vehicle present makes drivers pay more attention

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Takeaways

�Visual behaviors during ACC usage was different compared to standard cruise control or manually following a vehicle

�While differences were small across the sampled drivers, worth investigating further� Conditions such as drowsiness could have additional impact

� Individual drivers could exhibit larger differences

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Takeaways

�ACC a popular technology with truck drivers and has been available on heavy vehicles for several years

�As ADAS technology develops there could be new additions that take over additional functions� Steering control

� Platooning

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Takeaways

�Relatively minor differences observed here could become larger as automation takes over additional functions

�As automation progresses we need to ensure drivers stay engaged when they are expected to

�Particularly important on heavy vehicles that could weigh 80,000 pounds or have compromised brakes

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Thank you!

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