1. Exploration of the traffic flow impacts of combined lateral and longitudinal support Bart van Arem (TNO Inro) & Govert Schermers (AVV) Jaarbeurs, Utrecht, December 2003

2. Motivation Increase knowledge of risk and success factors for deploying lateral control systems Increase knowledge of risk and success factors for deploying lateral control systems –Traffic flow and safety –Acceptance –Infrastructure consequences –Other developments Increase awareness and acceptance of ADA systems in general Increase awareness and acceptance of ADA systems in general

3. Approach Field Operational test with LDWA Field Operational test with LDWA –Test fleet –Driving simulator –Acceptance –Infrastructure –Traffic flow Qualitative exploration Qualitative exploration –Lateral (LDWA and LKS) –Longitudinal (ACC and ACC+) Traffic flow simulation Traffic flow simulation –Effects of implementing CA in HGV sector

4. Questions Potential impacts of lateral support on capacity Potential impacts of lateral support on capacity –What degree of support? –Additional impact of combination with longitudinal support? –Compensate capacity decrease on narrow lanes? –Impact in relation to other in-car devices such as phones?

5. Literature Workload and attention theory – lower workload creates compensating behaviour, possibly non driving related causing a decrease in driving performance Workload and attention theory – lower workload creates compensating behaviour, possibly non driving related causing a decrease in driving performance Little on capacity, driving performance and lateral support Little on capacity, driving performance and lateral support Results of the impact of mobile phone use on driving ambiguous Results of the impact of mobile phone use on driving ambiguous Longitudinal support decreases workload (but will the driver compensate or relax?) Longitudinal support decreases workload (but will the driver compensate or relax?)

6. Qualitative traffic model Structures the relationship between driving behaviour and flow effects helps experts recognise effects of combinations

7. Expert consultation Individual polling on hypotheses on parts of traffic model Individual polling on hypotheses on parts of traffic model Workshop discussion of hypotheses in relation to literature Workshop discussion of hypotheses in relation to literature Synthesis of hypotheses into impacts on capacity Synthesis of hypotheses into impacts on capacity

8. Reference cases Capacity 6600 veh/h, with 20% heavy vehicles Capacity 6400 veh/h, with 20% heavy vehicles

9. A priori polling: capacity impacts Impacts LKS stronger than LDWA Impacts LKS stronger than LDWA Impact stronger on narrow lanes Impact stronger on narrow lanes ACC dominant impact ACC dominant impact No additional impact by combination of lateral and longitudinal No additional impact by combination of lateral and longitudinal VARIANT AVERAGE EFFECT STDEV LDWA, normal 0.9%1.7% LKS, normal 2.0%3.5% LDWA, narrow 1.9%3.1% LKS, narrow 5.1%6.3% LDWA/LKS+ ACC 4.5%5.3%

10. Reduction of workload –Only in case of active support –Consumers »Few »Degraded driving performance; less lane changes, longer reaction time; more perception errors –Active compensation: »Smaller headways »Use narrow lanes more often

11. Lane change behaviour –ACC, ACC+, LKS: decreased lane changes ‘enjoy the ride’ –Fewer lane changes: positive for capacity –Long platoon: possibly negative –LKS and narrow lanes: increased utilization of narrow lanes

12. Lateral position choice and passing behaviour Improved passing opportunities; decrease of ‘locking’ on narrow lanes Improved passing opportunities; decrease of ‘locking’ on narrow lanes Lack of preview: potentially unstable traffic Lack of preview: potentially unstable traffic

13. Intended speed and headway No impact of changes in intended speed on capacity No impact of changes in intended speed on capacity LKS compensated by short headway LKS compensated by short headway Larger headways of ACC/ACC+ lead to capacity decrease Larger headways of ACC/ACC+ lead to capacity decrease

14. Other Penetration level: Penetration level: –Negative impact at low penetration –Positive impact at high penetration

15. Capacity estimates after workshop AVERAGE STD DEV LDWA Normal lanes 0.7%0.9% Narrow lanes 0.5%0.4% LKS Normal lanes 0.3%2.1% Narrow lanes 3.3%1.7% LDWA + ACC Normal lanes 1.0%0.0% Narrow lanes 0.5%0.5% LKS + ACC + Normal lanes 5.0%3.7% Narrow lanes 8.8%7.9%

16. Summary capacity effects Impact LDWA on traffic performance limited Impact LDWA on traffic performance limited Decrease in workload with more active forms of driver support is enjoyed or compensated ® Decrease in workload with more active forms of driver support is enjoyed or compensated ® Traffic performance depends differently on enjoyers and compensators, in terms of headways, lane changing, reaction times ® Traffic performance depends differently on enjoyers and compensators, in terms of headways, lane changing, reaction times ® Impacts of lateral support is stronger on narrow lanes Impacts of lateral support is stronger on narrow lanes