ON-ROAD TESTING
Naturalistic Studies (Driving In Traffic) continued...
Self-reported at-fault crashes during the prior 12-month period were assessed using a questionnaire. The number of crashes per subject ranged from 0 to 4. Sixty-three percent of the subjects reported at-fault crashes over the previous year. The road test was administered by two driving instructors from the Belgian fitness-to-drive evaluation center in a car equipped with a dual brake. The 45-minute road test was conducted over a standardized 35-km (21.7 mi) route in and outside of town areas in Brussels and on a highway, and included maneuvers such as lane changing, turning left, and merging with traffic. Examiners completed a detailed evaluation grid that consisted of 11 dimensions, as follows. Each dimension was rated on two or more 3- and 4-point subscales.
- Lateral position on the road: lateral positioning and steady steering control
- Lane position change: lane choice
- Distance from the car in front: style and adaptation
- Speed: style and adaptation
- Visual behavior and communication: eye/hand movements, and contact with other road users
- Traffic signals: perception and reaction
- Mechanical operations: fluency and timeliness of steering and pedal control
- Anticipation: tactical anticipatory behavior in changing situations
- Understanding, perception, and quality of traffic participation: insight, sense of context, and practical implementation
- Turning left: specific situation, into main road
- Joining the traffic stream: specific situation on the highway
The evaluation grid was developed at the neuropsychology/gerontology department of the University of Groningen (the Netherlands) by Brouwer, Ponds, and van Woffelaar (1989). Content validity was addressed using driving assessment experts from the Dutch fitness-to-drive assessment Center and the CARA department of the Belgian Road Safety Institute. Consistent with the strategic-tactical-operational conception of driving associated with Michon (1985), the 11 dimensions assessed in this study were sorted into three scales. The scores on 3 dimensions (#5, #6, and #9 above) were combined to produce a visuo-integrative scale. The scores on 2 dimensions were combined to produce an operational scale (#1 and #7 above), reflecting psychomotor aspects of driving psychomotor. The scores on 4 dimensions (#2, #3, #4, and #8 above) were combined to produce a scale reflecting tactical choices (driving style).
De Raedt and Ponjaert-Kristoffersen (2001) found that the tactical and visuo-integrative scales each predicted at-fault crashes at crossroads, the crash type in which older drivers are most strongly overrepresented. The visuo-integrative scale also predicted rear-end and side-swipe crashes, for this older sample. The operational scale failed to predict at-fault crashes of any type.