Driving is an important functional activity in today’s society and people with whiplash associated disorders (WAD) frequently report driving as a major functional complaint. However, there is scant knowledge about driving in the chronic WAD population. In recognition of this deficit, the overall aim of this body of research was to increase understanding of driving problems, difficulties and performance in individuals with chronic WAD towards optimising driving for this group.
As a first step, it was necessary to clearly understand the problems with driving expressed by individuals with chronic WAD. The primary aim of Study 1 was therefore to determine troublesome driving tasks using a semi-structured interview. Thirty-three patients with chronic WAD participated. The most frequently nominated troublesome driving tasks were: checking blind spots, prolonged driving and reversing/reverse-parking. Ironically, not all of these driving tasks are included in current driving scales, suggesting that a new scale was required for the chronic WAD population.
In Studies 2 and 3, a self-report measure for driving difficulty suitable for a population with chronic WAD was developed. A 12-item Neck Pain Driving Index (NPDI) was created initially (Study 2) through assessments of: 1) content validity of driving tasks by an external panel, 2) flooring and ceiling effects and internal consistency and 3) the most appropriate category in a common framework of driving task performance (strategic, tactical and operational), categorized by the external panel. In a confirmation stage (Study 3), Rasch analyses were used to develop an appropriate scoring system and ensure unidimensionality in the strategic, tactical and operational driving performance levels of the NPDI. On the basis of Rasch analyses, the response format was modified and four tasks were removed to ensure unidimensionality of each NPDI level. Consequently, a 9-item NPDI was established.
The 9-item NPDI enabled investigation of the relationship between self-reported driving difficulty and relevant clinical features (Study 4). This study involved 40 WAD subjects and was conducted in a laboratory setting. Measures were made in three domains: 1) physical (range and maximum angular velocity of head rotation, performance during gaze stability and eye-head coordination, and visual dependency), 2) cognitive (self-reported cognitive and fatigue symptoms and Trail Making Tests), and 3) psychological (general stress, depression, traumatic stress, fear of neck movements and fear of driving). Each domain was assessed against each of the strategic, tactical and operational driving levels using hierarchical multiple regression analyses. This study demonstrated that while all domains correlated with self-reported driving difficulty, physical and cognitive impairments independently contributed to self-reported driving difficulty beyond neck pain, dizziness and symptom duration. These findings supported the need to investigate actual driving performance in those with chronic WAD.
Two studies were conducted using a state-of-the-art driving simulator. In Study 5, driving-related performance was compared between 17 WAD subjects and 26 controls. Driving was simulated in freeway, residential and city scenarios developed for this study. Driving-related performance was examined using an established measure with 12 parameters and divided attention tasks while driving. The WAD group demonstrated statistically poorer driving performance in some parameters but no parameters met a failing grade. Performance in divided attention tasks was comparable to the controls. Study 6 investigated neck motor performance (range and velocity of head rotation and upper trapezius muscle rest time), current neck pain intensity, fatigue and mental effort while driving in individuals with chronic WAD compared to healthy controls. Correlations were also investigated between the 9-item NPDI and neck motor performance, neck pain, fatigue and mental effort in the WAD group. For this study, 14 WAD subjects and 14 controls with complete data were analysed. The WAD group had no significant impairments in the two physical measures while driving, but displayed greater mental effort while driving compared with the controls. The NPDI moderately correlated with neck pain intensity and fatigue level before driving and maximum angular velocity of head rotation during driving (All P < 0.05).
This research has better defined the driving difficulties experienced by persons with chronic WAD. A specific questionnaire was developed to assess driving difficulties in the chronic whiplash population. A notable finding was that although driving difficulty is a common functional complaint in WAD, driving performance and safety were not compromised in the 15-minute driving simulator assessment. Further investigations are warranted with different settings (eg, longer driving and reversing) before it is possible to state that the driving performance of drivers with chronic WAD is comparable to healthy drivers. Although further investigations with a larger cohort of chronic WAD are necessary, the preliminary investigations in this thesis (Studies 4 and 6) suggest that there are possible links between self-reported driving difficulty and neck pain, dizziness and physical and cognitive impairments. Thus, management of physical and cognitive impairments may reduce self-reported difficulty in driving and enhance quality of life of people with chronic WAD.