International Journal of Industrial Ergonomics 35 (2005) 939–953 Situation awareness and workload in driving while using adaptive cruise control and a cell phone Ruiqi Ma, David B. Kaber Speaker: Jenny 2008/10/08

Introduction Driving tasks: perception, comprehension, projection, decision of action, and implement the action. Advanced automation technologies –improve safety, efficiency, and comfort –increased monitoring workload, and attention distraction. (Ward, 2000)

Existing theory on SA in driving 3 levels of SA: perception, comprehension, and projection. (Endsley, 1995) 3 general types of driving tasks: operational, tactical, and strategic. (Ward, 2000) (Matthews et al., 2001) Multiple elements of awareness defining driving SA: spatial, identity, temporal, goal, and system. (Matthews et al., 2001)

Existing theory on SA in driving System factors influence operator achievement of SA, including the number and complexity of automation systems. (Endsley, 1995) Critical knowledge to SA: navigation, environment and interaction, spatial orientation, and vehicle status knowledge.

Previous studies Intelligent transportation system includes ACC. Adaptive cruise control (ACC): adjust vehicle speed Long headway distance (2.4s):reduce the frequency of “tailgating” and the severity of rear- end collisions, lower driving workload. fewer safe brake: ACC may increase the accident from driver distraction, when performing more in-vehicle secondary tasks.

Impact Cell phone: driving workload ↑, SA ↓, task performance ↓. Limited mental resources Worse effect of cell phone conversation: caller can’t visualize the situation, and driver may use one hand to hold the phone hands-free cell phone: increasing the headway distance and decreasing speed to compensate the need for increased action time. (Chen and Lin, 2003)

Situation Awareness measure: –Location-recall probe –Performance probe –Scene-interpretation probe

1.Investigate the effects of ACC and cell phone use in driving on a direct and objective measure of SA and perceived driver workload 2.Access the competition of multiple driving and communication tasks for limited mental resources How to implement in-vehicle automation to facilitate and support driver SA How to balance driving and secondary tasks to ensure good SA and performance

Apparatus: medium fidelity driving simulation (C++), stereographic goggles, cell phone (Motorola T720)

Experiment design Four 25-min session 18 college students: 9 males and 9 females Independent variable –ACC control mode, cell phone use condition Dependent variable –driver SA (3 level: perception, comprehension, projection) Simulation freeze technique: SAGAT (situation awareness global assessment technique) SA questionnaire: recall car locations and colors, and traffic signs

Method--Task Changes in speed and lateral position Maintain car in the right-hand lanes of the 4-lane freeway keep car in the middle of a particular lane Observe road signs ACC / no-ACC control modes User car maximum speed: 80mph (Lead car speed: 60 mph) Headway distance: 2.4s Adjust the user car speed relative to lead car speed changes (1.4s) Cell phone: 10 arithmetic questions/ call (last less than 2mins)

Subjective workload: mental demand rating scale Participant accuracy: headway distance (optimal range: 8- 25m), following speed, lane tracking and maintenance on the straight and curve lanes

Hypotheses ACC system improves driver SA under no unexpected events ACC decrease mental workload— driver boredom and vigilance decreases over time without ACC control (Ward, 2000) Cell phone use would degrade driver task performance (Hancock et al., 1999,2002)

Results

Result—driver SA ANOVA Tukey Test In-vehicle automation: reduce driver task load, and improve driver SA Cell phone conversation: degrade driver comprehension and projection of state of the driving environment and overall SA

Results-driving workload

Results-driving performance Vehicle control is affected by ACC system, not cell phone conversation. Reason: the cell phone conversation is intermittent and didn’t pose a continuous secondary load on drivers.

Results-driving performance Headway distance

Results-driving performance Following speed

Results-driving performance Land maintenance on curves –There was a trend for greater lane maintenance deviations on curves when the ACC control was inactive. In summary, cell phone conversations during driving wouldn’t decrease task performance. (Since the duration is too short.)

Conclusion the importance of interaction with in- vehicle systems to human perception, comprehension, and projection of driving environment states. ACC under typical driving conditions could facilitate driver situation awareness. Agree with prior work (Parker et al., 2003), this study found improvements in variation in headway distance and following speed control with ACC.

conclusion Hand-held cell phone use can be harmful to driver SA. (Gugerty et al, 2003) Chen and Lin(2003) showed significant driving performance decrease due to cell phone use, but this study didn’t get the same result. Similar to Rudin Brown et al.(2003) results, we found that the benefits of ACC, in terms of workload reduction, were offset by workload increases due to cell phone use.