driving behaviour effects of the chauffeur assistant

tTNO Human Factors

Driving behaviour effects of the Chauffeur Assistant

Jeroen Hogema

16 December 2003 2t

Overview• Background• Method

• TNO driving simulator• Simulating the CA• Experimental design

• Results• Conclusions

• consequences for traffic simulation model

16 December 2003 3t

Dutch Evaluation of the Chauffeur Assistant (DECA)• Chauffeur Assistant

• Adaptive Cruise Control• Lane Keeping System

• Follow-up of Lane Departure Warning Assistant FOT

• Transport Research Centre (TRC) • Ministry of Transport, Public Works, and Water Management

16 December 2003 4t

Chauffeur Assistant: QuestionsIndividual driver level• driving behaviour• workload• acceptance

traffic flow level• traffic performance• safety indicators

16 December 2003 5t

DECA

DRIVING SIMULATO

R behaviour

TNO

MIXIC

interpretationreport

MIXIC simulation

s

TRC

workload

acceptance

driver

CA

CA

16 December 2003 6t

Method – Driving simulator

• visual• audio• steering

force• motion

16 December 2003 7t

Method – Driving simulator• DAF 95XF lorry• Mass 20500 kg (fully loaded)• Maximum engine power: 350

kW

• Parameter set from DAF trucks

16 December 2003 8t

Method – Simulating the CA• Adaptive Cruise Control

DC specifications• Distance law for car-following

• Dref = 6.0 + 1.3 * v• Dref = ACC's intended following distance (m)• v=current speed (m/s)•

• Braking: max. -3 m/s2

16 December 2003 9t

Method – Simulating the CA• ACC controller

• structure from earlier work

• parameters from recent ACC work by TNO Automotive

16 December 2003 10t

Method – Simulating the CAACC reference scenarios• approaching• braking lead car• accelerating lead car• cut-in

Dynamic behaviour of• reference model• driving simulator CA• MIXIC CA

0 10 20 30 40 50 6020

21

22

23

spee

d (m

/s)

Scenario 3

DS ref

0 10 20 30 40 50 6010

20

30

40

dist

(m) DS

ref

0 10 20 30 40 50 60-2

-1

0

1ac

c

time (s)

DS ref

16 December 2003 11t

Method – Simulating the CALKS• noise added to obtain realistic servo

performance• SDLP about 10 cm

0 50 100 150 200 250 300-0.2

0

0.2

y (m

)

Scenario 101

0 50 100 150 200 250 300-0.5

0

0.5

fi(de

gr)

0 50 100 150 200 250 300-1

0

1

2

dels

(deg

r)

time (s)

lateral position,heading angle

wheel angle state

vehicle

gear ratio

delta_ref

control loader

Noise

. steer.whl.angle

LKS

16 December 2003 12t

Method - Experimental design (1)• with vs without CA• traffic volume

• low (3400/u) • high (6000/u)

• 3-lane motorway, 3.5 m wide lanes

ACC headway• Dref = 6.0 + tk * v• tk = 1.0 – 1.3 – 1.6 s

• 1 preferred setting selected by each driver prior to experiment

16 December 2003 13t

Method - Experimental design (2)Scenarios• car-following (overtaking possible)• braking lead car

• 3 m/s2

• 4 m/s2

Subjects• 18, professional truck drivers• at least 5 years 'groot rijbewijs'• age between 25-55• paid for their participation

16 December 2003 14t

Human Machine Interface

• driver turns CA turns on/off • switches• brake pedal

• driver sets ACC speed• buzzer at maximum

braking

display• ACC set speed on

speedometer• symbol: headway control

or speed control

16 December 2003 15t

Results – preferred CA time headway1.0 s 1 x1.3 s 8 x1.6 s 9 xTotal 18 x

16 December 2003 16t

Results – SD lateral position• effect of CA

low vo lum e high vo lum e

without with

C A

0.0

0.1

0.2

0.3

0.4

0.5

SD

LP (m

)

16 December 2003 17t

Results – Time to Line Crossing• effect of CA

low vo lum e high vo lum e

without with

C A

2.0

2.5

3.0

3.5

4.0

TLCm

in (s)

16 December 2003 18t

Results – close following• effect of CA

low vo lum e high vo lum e

without with

C A

0

1

2

3

4

5

% TH

W < 1 s

16 December 2003 19t

Results – lane change frequency• effect of CA on edge of marginal significance

[p<.11]

low vo lum e high vo lum e

without with

C A

5

6

7

8

9

lane changes (/15 min)

16 December 2003 20t

Braking lead car: lane change response

CA Changes lanewithout 37 out of 103 36%with 17 out of 107 16%

lane change reaction of subject

Fewer lane changes with CA

decel. Changes lane3 m/s^2 26 out of 127 20%4 m/s^2 24 out of 67 36%

16 December 2003 21t

Braking lead car: braking response

leader decel. subject max. dec.3 m/s^2 3.5 m/s^24 m/s^2 4.3 m/s^2

braking reaction of subject

lower deceleration levels with CA

CA subject max. dec.without 4.3 m/s^2with 3.5 m/s^2

16 December 2003 22t

Results – mental effort• Rating Scale of Mental Effort• effect of CA

without with

C A

30

40

50

60

70

RS

ME

somewhat

ra ther

high vo lume low vo lume

16 December 2003 23t

Acceptance (1)

 Mean Std.Dev.

useful-useless 1.2 0.7

pleasant-unpleasant 1.3 0.9

good-bad 1.1 0.8

nice-annoying 0.9 1.1

effective-superfluous 1.1 0.9

likeable-irritating 1.3 0.7

assisting-worthless 1.4 0.8

desirable-undesirable 1.2 0.9

raising alertness-sleep inducing -0.2 1.1

• -2..2 scales:

16 December 2003 24t

Acceptance (2)Underlying variables

• USEFULNESS: + 0.93• SATISFACTION: + 1.10

16 December 2003 25t

Summary of results (1)With Chauffeur

Assistant…• reduced SD of lateral

position• higher Time to Line

Crossings • less short time

headways• reduced Mental Effort• (fewer changes with

CA?)

16 December 2003 26t

Summary of results (2)• Acceptance: positive

• except “sleep-inducing”

Lane changes• fewer changes with CA?

Braking lead car• fewer lane changes with

CA• less critical behaviour

with CA (maximum deceleration, minimum TTC)

No effects on:• mean, s.d. speed• lane use (% right

lane)• mean lateral position• mean time headway

16 December 2003 27t

Chauffeur Assistant in MIXIC

driver vehicle

CA

16 December 2003 28t

Chauffeur Assistant in MIXICDRIVER

VEHICLE

CA

car following

free driving

lane change model

LATERAL

LONGITUDINAL

settingstransitions

CA

16 December 2003 29t

MIXIC driver modelDriver – CA• CA settings

• CA reference speed = driver’s intended speed• CA reference headway: 50% 1.3 s; 50% 1.6 s

• CA off when:• CA is braking hard AND driver would brake harder• starting lane-change manoeuvre

• CA on when:• “possible”

16 December 2003 30t

MIXIC driver modelLane change behaviour• small effects• nature of effects unknown

• tactical level: avoid getting 'stuck' in car-following in a 'slow' lane

• driver-state related: reduced alertness, complacency, less 'active' driving

• => no changes in lane change model

16 December 2003 31t

Conclusions

• Behaviour• Workload effects in line with ACC or LKS

research• Acceptance

}Chauffeur Assistant – ACC + LKS:

contribution of ACC and LKS unknown

Minor modifications to MIXIC->driver->ACC model