Exploration of the traffic flow Exploration of the traffic flow impacts of combined lateral and impacts of combined lateral and

longitudinal supportlongitudinal support

Bart van Arem (TNO Inro) & Bart van Arem (TNO Inro) & Govert Schermers (AVV) Govert Schermers (AVV)

Jaarbeurs, Utrecht, December 2003Jaarbeurs, Utrecht, December 2003

MotivationMotivation

Increase knowledge of risk and success Increase knowledge of risk and success factors for deploying lateral control systemsfactors for deploying lateral control systems– Traffic flow and safetyTraffic flow and safety– AcceptanceAcceptance– Infrastructure consequencesInfrastructure consequences– Other developmentsOther developments

Increase awareness and acceptance of ADA Increase awareness and acceptance of ADA systems in generalsystems in general

ApproachApproach Field Operational test with LDWAField Operational test with LDWA

– Test fleetTest fleet– Driving simulatorDriving simulator– AcceptanceAcceptance– InfrastructureInfrastructure– Traffic flowTraffic flow

Qualitative explorationQualitative exploration– Lateral (LDWA and LKS)Lateral (LDWA and LKS)– Longitudinal (ACC and ACC+)Longitudinal (ACC and ACC+)

Traffic flow simulationTraffic flow simulation– Effects of implementing CA in HGV sectorEffects of implementing CA in HGV sector

QuestionsQuestions

Potential impacts of lateral support on Potential impacts of lateral support on capacitycapacity– What degree of support?What degree of support?– Additional impact of combination with Additional impact of combination with

longitudinal support?longitudinal support?– Compensate capacity decrease on narrow Compensate capacity decrease on narrow

lanes?lanes?– Impact in relation to other in-car devices such Impact in relation to other in-car devices such

as phones?as phones?

LiteratureLiterature Workload and attention theory – lower workload Workload and attention theory – lower workload

creates compensating behaviour, possibly non creates compensating behaviour, possibly non driving related causing a decrease in driving driving related causing a decrease in driving performanceperformance

Little on capacity, driving performance and lateral Little on capacity, driving performance and lateral supportsupport

Results of the impact of mobile phone use on Results of the impact of mobile phone use on driving ambiguousdriving ambiguous

Longitudinal support decreases workload (but will Longitudinal support decreases workload (but will the driver compensate or relax?)the driver compensate or relax?)

Qualitative traffic modelQualitative traffic modelStructures the relationship between driving behaviour and flow effectsStructures the relationship between driving behaviour and flow effects

helps experts recognise effects of combinationshelps experts recognise effects of combinations

mix of vehicletypes (per lane)15

speed distribution(per lane)11

speed differencebetween lanes12

vehicle width dis-tribution (per lane)16

lateraldistances9

formation ofplatoons / empty

zones / locking6

roadwaycapacity1

lane capacity2 distributionover lanes3

gross followingdistances4

net followingdistances5

speed limit17 prohibition

for trucks18 overtaking pro-

hibition for trucks19 availability

shoulder lane20width left margin/

distance to barrier21

lane width24

Intendedheadways forcar following

10

Intended speed(per lane)14

lane changebehaviour7

passingbehaviour8

reaction time23

lateral positionchoice13

stability carfollowing

/ platoons22

Expert consultationExpert consultation

Individual polling on hypotheses on parts of Individual polling on hypotheses on parts of traffic modeltraffic model

Workshop discussion of hypotheses in Workshop discussion of hypotheses in relation to literaturerelation to literature

Synthesis of hypotheses into impacts on Synthesis of hypotheses into impacts on capacity capacity

Reference casesReference casesCapacity 6600 veh/h, with 20% heavy vehicles

Capacity 6400 veh/h, with 20% heavy vehicles

A priori polling: capacity impactsA priori polling: capacity impacts Impacts LKS stronger than LDWAImpacts LKS stronger than LDWA Impact stronger on narrow lanesImpact stronger on narrow lanes ACC dominant impactACC dominant impact No additional impact by combination of lateral and longitudinalNo additional impact by combination of lateral and longitudinal

VARIANTVARIANTAVERAGE EFFECTAVERAGE EFFECT STDEV STDEV

LDWA, normalLDWA, normal 0.9%0.9% 1.7%1.7%

LKS, normalLKS, normal 2.0%2.0% 3.5%3.5%

LDWA, narrowLDWA, narrow 1.9%1.9% 3.1%3.1%

LKS, narrowLKS, narrow 5.1%5.1% 6.3%6.3%

LDWA/LKS+ ACCLDWA/LKS+ ACC 4.5%4.5% 5.3%5.3%

Reduction of workloadReduction of workload

– Only in case of active supportOnly in case of active support– ConsumersConsumers

» FewFew» Degraded driving performance; less lane changes, Degraded driving performance; less lane changes,

longer reaction time; more perception errorslonger reaction time; more perception errors– Active compensation: Active compensation:

» Smaller headwaysSmaller headways» Use narrow lanes more oftenUse narrow lanes more often

Lane change behaviourLane change behaviour

– ACC, ACC+, LKS: decreased lane changes ACC, ACC+, LKS: decreased lane changes ‘enjoy the ride’‘enjoy the ride’

– Fewer lane changes: positive for capacityFewer lane changes: positive for capacity– Long platoon: possibly negativeLong platoon: possibly negative– LKS and narrow lanes: increased utilization of LKS and narrow lanes: increased utilization of

narrow lanesnarrow lanes

Lateral position choice and passing Lateral position choice and passing behaviourbehaviour

Improved passing opportunities; decrease of Improved passing opportunities; decrease of ‘locking’ on narrow lanes‘locking’ on narrow lanes

Lack of preview: potentially unstable trafficLack of preview: potentially unstable traffic

Intended speed and headwayIntended speed and headway

No impact of changes in intended speed on No impact of changes in intended speed on capacity capacity

LKS compensated by short headwayLKS compensated by short headway Larger headways of ACC/ACC+ lead to Larger headways of ACC/ACC+ lead to

capacity decreasecapacity decrease

OtherOther

Penetration level: Penetration level: – Negative impact at low penetration Negative impact at low penetration – Positive impact at high penetrationPositive impact at high penetration

Capacity estimates after workshopCapacity estimates after workshop

AVERAGEAVERAGE STD DEVSTD DEV

LDWALDWA Normal lanesNormal lanes 0.7%0.7% 0.9%0.9%

Narrow lanesNarrow lanes 0.5%0.5% 0.4%0.4%

LKSLKS Normal lanesNormal lanes 0.3%0.3% 2.1%2.1%

Narrow lanesNarrow lanes 3.3%3.3% 1.7%1.7%

LDWA + ACCLDWA + ACC Normal lanesNormal lanes 1.0%1.0% 0.0%0.0%

Narrow lanesNarrow lanes 0.5%0.5% 0.5%0.5%

LKS + ACCLKS + ACC++ Normal lanesNormal lanes 5.0%5.0% 3.7%3.7%

Narrow lanesNarrow lanes 8.8%8.8% 7.9%7.9%

Summary capacity effectsSummary capacity effects

Impact LDWA on traffic performance limitedImpact LDWA on traffic performance limited Decrease in workload with more active forms of Decrease in workload with more active forms of

driver support is enjoyed or compensated ®driver support is enjoyed or compensated ® Traffic performance depends differently on Traffic performance depends differently on

enjoyers and compensators, in terms of headways, enjoyers and compensators, in terms of headways, lane changing, reaction times ®lane changing, reaction times ®

Impacts of lateral support is stronger on narrow Impacts of lateral support is stronger on narrow laneslanes