This document summarizes observations from a study on driver interactions with in-vehicle cruise control, speed limiter, and speed alert technologies. The following were observed: 1) Cruise control helped maintain speed but did not prevent driving too fast, and caused problems during passing maneuvers or when adapting speed. 2) Speed limiters also helped with speed keeping but did not prevent speeding, and had issues recognizing changing limits or distractions while setting speed. 3) Speed alerts did not significantly change driving behavior but did increase issues with following distance and driver communication errors. In conclusion, while these systems helped with speed keeping, they did not prevent all speeding and caused new problems in some situations related

1. Understanding driver interactions
with In-Vehicle Technologies
Behaviour Observations
Clemens Kaufmann (FACTUM)
Ralf Risser (FACTUM)
INTERACTION Final Event
22 November 2012, Brussels

2. Behaviour observations – Wiener Fahrprobe
• Each test persons observed twice
(with/without system active)
• Two observers with different tasks
– Coding observer
– Free observer
• Results from both observers

3. Sample Cruise Control
Country CC
Czech Republic 15
Finland 15
France 15
The Netherlands
Portugal 8
Spain 9
UK 15
Total (N) 77

4. Cruise Control
• Used on highways
• Speed selection variables
– According to the limits
– Higher than the limits (up to 30km/h higher)
– Lower than the limits (according to the traffic
situation)
– Hardly/never changed vs. speed changed
quite often

5. Results Cruise Control
• No differences between the rides with and
without activated CC regarding:
– Longitudinal control
– Lateral control
– Obeying traffic rules
– Interaction with other road user
– Antcipation
• Significantly less driving too fast with CC

6. Problems with Cruise Control
• Problems with CC
– Too fast according to the limits and situations
– Approaching other cars without changing the speed
– Overtaking manouvers
 Takes long time to overtake other cars
 Abort overtaking manouver
 Driving too close to the car in front
 Overtaking on the right side
• Conflicts only observed on the rides with an
active CC

7. Conclusion Cruise Control
• CC helps keeping the speed
• but does not prevent from driving too fast
• Problems in situation when speed has to
be adapted
– Overtaking manouvers
– Slower car in front
– Exiting the highway
• Inexperienced users claimed to have
problems (functions & interface)

8. Sample Speed Limiter
Country SL
Czech Republic
Finland
France 15
The Netherlands
Portugal 8
Spain 9
UK
Total (N) 32

9. Issues related to Speed
• Used on rural roads and urban areas
• Speed selection in the system
– Mostly according to the limits
– Higher than the limits (up to 30km/h)
– Lower than the limits (20 km/h lower)
– Speed was changed as soon as the speed limit
changed
– Speed was set in the beginning and never changed
– Using two speeds – one for rural roads one for
urban areas

10. Results Speed Limiter
• No differences between the rides with
and without an activated SL regarding
– Speed behaviour
– Longitudinal control
– Lateral control
– Obeying traffic rules
– Interaction with other road user
– Antcipation

11. Problems with Speed Limiter
• Problems while using SL
– Not recognising the change of the
speed limit
– Distraction while setting speed
– Misinterpreting signals
• Conflicts (right-angle, rear-end,
vulnerable road user) more often
observed while using the system

12. Conclusion Speed Limiter
• SL helps keeping the speed
• but does not prevent from driving too fast
• Problems in situations
– When speed limit changes
– Handling with the system
– System is not well known

13. Sample Speed Alert
Country SA
Czech Republic
Finland
France
The Netherlands 20
Portugal
Spain
UK 15
Total (N) 35

14. Use of Speed Alert
• Used on rural roads and in urban areas
• SA function of the NS was used
• Most of the times speed was immediately
reduced after warning

15. Results Speed Alert
• No differences between the rides with and
without an activated SA regarding
– Speed behaviour
– Lateral control
– Obeying traffic rules
– Antcipation
• Significantly more often too close to the car in
front
• Significantly more erros in the communication
behaviour

16. Problems with Speed Alert
• Problems while using SA
– No major differences in the driving behaviour
– More often shorter distances to the car in front
– More errors in the interaction with other road users
(indicating behaviour, against vulnerable road
users)
– Similar conflict (right-angle, head-on) situations with
and without the system

17. Conclusion Speed Alert
• Especially problems with distance
keeping and interaction
• Observers found it difficult to ascribe
differences in the behaviour to the use of
the SA

18. Advantages and Problems of
Speed Regulating Systems
• Advantages
– Systems help the test persons to keep the speed
– No major influence on the driving behaviour
• Problems
– In specific situations when speeds has to be adapted
– Handling with the system (especially when system is
new)
– Systems are used in a not wished for way

19. Thank you for your attention