Retrospective cohort study of accident outcomes for individuals who have successfully undergone driver assessment following stroke
Alison M. Pearce MPH, BAppSc (OT); Research Officer. Jan M. Smead BAppSc (OT); Occupational Therapist. Ian D. Cameron FAFRM (RACP), PhD, MBBS; Professor.
Jan M. Smead, Driver Assessment and Rehabilitation Centre, Royal Rehabilitation Centre Sydney, PO Box 6, Ryde, NSW 2112, Australia. Email: firstname.lastname@example.org
Background: The occupational role of ‘driver’ is highly valued. Stroke can have a significant impact on an individual’s ability to drive safely. Multi-disciplinary driver assessments are conducted to assess the safety of post-stroke individuals returning to driving, however, little follow-up of drivers following successful assessment has been performed.
Aim: The objective of this study was to investigate whether passing a multi-disciplinary driving assessment following stroke predicted medium- to long-term safe and confident driving.
Methods: A retrospective cohort study with primary data collection through structured telephone interviews was undertaken. Respondents were individuals post-stroke aged 18–74 years who had successfully passed a multi-disciplinary driver assessment.
Results: Forty-five respondents were interviewed an average of 20 months following the assessment. Forty individuals were still driving. Twenty-five driving respondents reported driving in conditions that indicated confident driving. Confident driving was measured by driving frequency and distance, night driving, freeway driving and driving alone. The frequency of accidents and incidents suggests that 95% (n = 38) of drivers are ‘safe’. Eight respondents reported accidents, one of which was major. In two accidents the respondent was ‘at fault’. A crash rate of 222 per 100,000 drivers is within the confidence interval for similar accidents in New South Wales.
Conclusions: The results of this small cohort study suggest that a multi-disciplinary driver assessment may be effective in identifying people following stroke with the ability to drive safely and confidently.
Each year in Australia approximately 60,000 people have a stroke (National Stroke Foundation, 2010). Many people following stroke may experience deficits such as reduced reasoning, confusion and slowed cognitive processing, which may lead to incorrect or unsafe responses in driving situations (Lings & Jensen, 1991). Society places a high value on the occupational role of ‘driver’, with connotations of independence, and associations with expanded work and social opportunities (Liddle et al., 2009). Between 30% and 50% of people return to driving following stroke or acquired brain injury (Fisk, Owsley & Pulley, 1997; Van Zomeren, Brouwer & Minderhoud, 1987).
There is low level evidence that drivers following stroke have no greater incidence of being involved in a motor vehicle accident or receiving a driving violation than drivers in the general population (Haselkorn, Mueller & Rivara, 1998; Lundqvist, Alinder & Ronnberg, 2008; Schanke, Rike, Molmen & Osten, 2008; Van Zomeren et al., 1987). This may be due to the adoption of compensatory strategies similar to those used by elderly drivers, although there is no direct evidence of this in stroke patients (De Raedt & Ponjaert-Kristoffersen, 2000; Fisk et al., 1997; George, Clark & Crotty, 2006; Unsworth, Wells, Browning, Thomas & Kendig, 2008). Older drivers who learn and use compensatory strategies such as avoiding peak hour traffic, driving in daylight and driving only in familiar areas, can reduce their accident level to that of, or lower than, technically better drivers (De Raedt & Ponjaert-Kristoffersen, 2000).
Given the potential for unsafe drivers to place themselves and others at risk, it is an important public health issue to accurately determine driving safety. Many studies have identified the tendency of drivers to overestimate their driving ability in relation to others (Delhomme, 1991; Groeger & Brown, 1989), including studies of individuals post-stroke and their spouses which found that both consistently over-rate the individual’s ability to drive (Heikkila, Korpelainen, Turkka, Kallanranta & Summala, 1999). Therefore, assessment by an independent means is required.
The literature most commonly describes a multi-disciplinary team which conducts a combination of off-road cognitive-perceptual assessments and an on-road driver assessment (Fisk et al., 1997; Galski, Ehle, Mcdonald & Mackevich, 2000; Heikkila et al., 1999; Mazer, Korner-Bitensky & Sofer, 1998; Ponsford, Viitanen, Lundberg & Johansson, 2008). Many of the off-road cognitive or perceptual assessments have limited evidence of reliability and validity (Unsworth, Lovell, Terrington & Thomas, 2005), and as few as 5% of driving assessors base their decisions on safety to drive on the off-road cognitive or perceptual assessments alone (Mazer et al., 1998). The on-road driver assessment component has been found to be the most important component of the comprehensive driving assessment procedure, and there is a growing body of research around the validity and reliability of these tests (Kay, Bundy & Clemson, 2009; Ponsford et al., 2008).
In Australia, the multi-disciplinary driving assessment teams include an occupational therapist, medical practitioner and driving instructor. It may also include an orthoptist, a neuropsychologist and with stroke patients the involvement of their neurologist. The occupational therapists’ role in these teams is to conduct practical driver assessments to complement medical assessments (Austroads, 2006). Although in New South Wales (NSW), where this study was conducted, the final decision regarding safety to return to driving rests with the Licensing Authority in that State, these decisions are based on the recommendations of the team, and specifically the report by the occupational therapist regarding on-road driving skills and ability (Austroads, 2006). In all states, the occupational therapist plays a key role in decisions regarding safety to return to driving.
Limited follow-up of drivers following stroke and successful driving assessment has been conducted, with no Australian-based follow-up studies identified. Katz et al. (1990) reviewed 22 drivers following stroke up to five years after their successful assessment, and concluded that ‘selected patients who have passed comprehensive driving assessments … are as fit to drive as are their normal matched controls’ (Katz et al., 1990, p. 136). Their matched control design allowed comparison between controls and patients of neuropsychologic profiles and accident rates.
A Canadian study surveyed stroke patients 4–5 years after their driving assessment to assess transport use, including driving habits (Finestone et al., 2009). Of the 106 individuals surveyed, 70 continued to drive. More than one-third of drivers reported self-imposed driving restrictions (Finestone et al., 2009). They also asked about driving record and found no significant difference between post-stroke drivers and a literature-based control group of drivers without stroke in recorded infringements.
A Norwegian study conducted longer-term follow-up of 65 patients 6–9 years after stroke to assess accident rates and driving fitness after successful assessment (Schanke et al., 2008). The patients had made considerable changes to their driving patterns from their pre-injury driving, but there was no significant difference in accident rates when compared with national normative data.
The aim of this study is to investigate whether passing a multi-disciplinary driver assessment conducted by an occupational therapy driver assessor, medical practitioner and driving instructor predicted medium- to long-term safe and confident driving. Safe driving was defined as no major accidents and no more than one minor accident or incident since the assessment. Confident driving was measured by the conditions in which a person drove, including driving frequency and distance, night driving, freeway driving and driving alone.
A retrospective cohort study was conducted, with the primary data collection through a structured telephone interview. The Royal Rehabilitation Centre Sydney’s Clinical Care Review Committee and the Quality Council and Board granted approval for the conduct of the interviews. Informed consent was obtained from all participants.
The interview was conducted with drivers seen by a driver assessment and training programme at a public rehabilitation hospital between February 1998 and August 2000 (inclusive). All clients aged less than 75 years referred to the programme following a stroke and who had passed both the on- and off-road assessment were eligible to participate. Clients over 75 years were excluded because, regardless of medical condition, driving performance and safety decreases and accident levels increase in drivers 75 years or over (Fildes, 1997). All the clients were referred by a doctor and were assessed by a driver-trained occupational therapist and a licenced driving instructor.
A total of 83 drivers were eligible for inclusion in the study at January 2001, when recruitment occurred. Drivers were interviewed between 6 and 36 months post-assessment and the mean time since assessment was 20 months.
In the absence of an existing tested questionnaire, this study used a structured telephone interview developed by the authors (based on the survey design used by Fisk et al., 1997). A pilot study with five clients indicated that people responded well to the questionnaire. A mixture of open and closed questions addressed driving status, car details and the conditions in which respondents drove. The conditions were driving alone, at night or on highways, driving frequency and the average distance driven per trip. A measure of driving confidence was collected using a Likert scale question asking ‘how safe do you feel when driving?’ (very safe, safe, neutral, unsafe and very unsafe). The details of any incidents and accidents since the assessment were obtained. Those respondents who were no longer driving were asked when and why they ceased driving and for details of any incidents or accidents prior to driving cessation.
This study defined an ‘incident’ to involve one vehicle, only causing minor damage to the car or another object. An ‘accident’ involved at least two vehicles, causing damage to at least one vehicle. A ‘major’ incident or accident was differentiated from a ‘minor’ event by involving injury, tow trucks or the police. Comparison data for rates of accidents were obtained from the NSW Roads and Traffic Authority (RTA) annual crash statistics. As the incidents contain only one car, they will always be at the fault of the driver and therefore fault was not attributed in these cases. For accidents, ‘fault’ was attributed by the NSW Road Rules 2008 based on the information provided by the driver. To be considered ‘safe’ an individual would have had no major accidents and no more than one minor accident or incident since the assessment.
The questions regarding driving conditions were designed to allow the number of more complex conditions in which clients drove to be considered as a measure of driving confidence. The conditions were selected on the basis that each requires different skills and abilities to be safely negotiated, and therefore the more conditions a person drives in, the greater the breadth of their skill can be perceived to be. In addition, it is assumed that the greater the number of complex conditions a person chooses to drive in, the higher their level of confidence in their driving ability (Marottoli & Richardson, 1998).
The telephone interview took 10–20 minutes and was conducted by an occupational therapist independent of the driver assessment programme. The interviewer attempted to interview each driver personally. If a driver was unavailable because of disability or language deficits, the interviewer obtained information from a relative or carer who was familiar with the drivers’ medical and driving history. Qualitative responses were recorded verbatim. Each interview respondent was given a unique identification number, and all identifying information was removed from the interview record to ensure confidentiality. The protocol was to call a given number a maximum of three times in one day and to wait at least two hours between calls. If a telephone number was disconnected or an answer could not be obtained after five attempts, this was recorded as a ‘no answer’.
Data were analysed in Microsoft Excel. Descriptive statistics, including frequency values and measures of central tendency were calculated. Confidence intervals were calculated using the Wilson score method to provide an estimation of the precision of the results. For ease of interpretation the results of these analyses are presented as a rate per 100,000 drivers.
The RTA crash statistics conform to the National Guidelines for the reporting of road vehicle crashes. The criteria for the inclusion of an accident are that the crash was reported to the police, occurred on a road open to the public, involved at least one moving vehicle and either involved at least one person being injured or killed or at least one motor vehicle being towed away (NSW Centre for Road Safety, 2009). Crashes are reported as fatal, injury or non-casualty events, and can be broken down by a number of variables related to the individuals involved, the type of vehicles involved and the environment involved in the crash (NSW Centre for Road Safety, 2009).
The demographics of the sample are given in Table 1. Of the 83 eligible drivers, 45 respondents were interviewed, giving a 54% response rate. Of the non-respondents, the majority were not recruited because of an inability to make telephone contact (n = 28). Of those who were contacted a variety of reasons for not participating were given, including having had a further stroke or deterioration in medical condition (n = 6), client deceased (n = 1) or a lack of time (n = 3). The mean age of the respondents was 59 years with a range of 18–74.
Table 1. Demographics of interview respondents
|Age† (n = 45)|
| 15–24||1 (2.2)|
| 25–34||1 (2.2)|
| 35–44||2 (4.4)|
| 45–54||8 (17.8)|
| 55–64||13 (28.9)|
| 65–74||18 (40.0)|
| Unknown||2 (4.4)|
|Gender (n = 45)|
| Male||29 (64.4)|
| Female||16 (35.6)|
|Months since assessment (n = 40)|
| 6–12||13 (32.5)|
| 13–24||15 (37.5)|
| 25–36||12 (30.0)|
|Location of stroke (n = 45)|
| Right sided||15 (33.3)|
| Left sided||15 (33.3)|
| Sub-arachnoid haemorrhage||1 (2.2)|
| Unknown||14 (31.1)|
Forty respondents were still driving at the time of the interview. The remaining five were no longer driving for a variety of reasons. Two respondents considered lack of confidence in their driving skill to be the primary reason for not driving. The other reasons given were a lack of finance to purchase a modified vehicle, the need for new glasses to comply with a conditional licence and having suffered a second stroke.
The results of the conditions in which people drove are summarised in Table 2.
Table 2. Driving conditions reported by interview respondents
|Driving status (n = 45)|
| Still driving||40 (88.9)|
| Ceased driving||5 (11.1)|
|Transmission type (n = 40)|
| Manual||7 (17.5)|
| Automatic||33 (82.5)|
|Driving frequency (n = 40)|
| Weekly or less||6 (15.0)|
| Every 2–3 days||13 (32.5)|
| Daily||21 (52.5)|
|Distance travelled per trip (km; n = 40)|
| < 5||5 (12.5)|
| 5–10||9 (22.5)|
| 11 or more||26 (65.0)|
|Driving at night (n = 40)|
| Yes||29 (72.5)|
| No||11 (27.5)|
|Driving alone (n = 40)|
| Yes||40 (100.0)|
| No||0 (0.0)|
|Freeway driving (n = 40)|
| Yes||35 (87.5)|
| No||5 (12.5)|
|Driving confidence (n = 40)|
| Feel safe||40 (100.0)|
| Do not feel safe||0 (0.0)|
The majority of clients still driving drove automatic vehicles (n = 33). For one subject, an automatic car was an essential condition on their licence. Over half of respondents (n = 21) drove daily. Two respondents had licence restrictions allowing them to travel only within a 5-km area.
The average age of respondents not driving at night (n = 11) was 65 years. Reasons for not driving at night included not required (n = 5), poor night vision (n = 2), decreased confidence (n = 2) and no night driving as a preexisting status (n = 2). In contrast, two respondents stated that they preferred to drive at night, either because of reduced traffic or personal preference.
The question of driving alone related to whether respondents required someone to be in the car while they were driving. A ‘yes’ answer to driving alone (n = 40) indicated confidence to drive independently.
Five respondents stated that they did not drive on highways or freeways. Four respondents stated that they drove only short distances, with no need to use highways or freeways, with two of these respondents having 5-km radius-restricted licences. The fifth respondent stated that they avoided highways as they were more cautious following the stroke. The average age of respondents not driving in these conditions was 61 years.
When questioned, all respondents reported that they felt safe when driving. Eight respondents said that they are now more cautious and this made them feel safer when driving. Three respondents felt safer than when they had initially completed the driving assessment, with one of these respondents having completed an Advanced Driver Training Course. Three drivers reported that they felt safe only because they drove in areas or over routes with which they were familiar.
The total number of conditions in which people drove was considered to be a measure of driving confidence. Twenty-five drivers reported driving in all five conditions (driving more frequently than weekly, more than 5 km per trip, alone, at night and on freeways). Of those driving in four conditions (n = 8), night driving was the condition the majority (n = 5) chose not to drive in. All three drivers who reported driving in only three conditions reported not driving in the same conditions; less than weekly and night driving. Of the three drivers who report driving in two conditions, all reported not driving on highways or over 5 km. A single respondent (n = 1) reported driving alone as the only condition in which they drove.
Given the definition of ‘safe’ drivers as those with no major accidents and no more than one minor accident or incident since the assessment, 38 of the 40 (95%) drivers interviewed were considered safe.
Incident and accident rates
Nine respondents reported 10 minor incidences. Examples of a minor incident included the subject scraping the wheel or hubcap against a gutter (n = 2) or scraping the side of the car against a pillar in a car park (n = 2). Four of these incidences occurred at home and two at work. Eight were sustained while parking and at least four happened whilst the driver was reversing the car. Seven minor accidents and one major accident were reported. Of these accidents, the driver was considered ‘at fault’ in one minor and one major accident. An example of a minor accident was being rear-ended at traffic lights (n = 1), while the single major accident occurred when the driver was turning right at a major intersection and failed to give way to a car which was ‘running’ an orange light.
Respondents involved in accidents were between 12 and 27 months post-assessment at the time of the accident (mean = 19.2 months). The single major accident occurred in an individual in the youngest age group, who reported no other incidents or accidents and drove in all conditions.
The RTA crash statistics reported 42,833 crashes in 2008, of which 38,109 were car crashes (NSW Centre for Road Safety, 2009). The reference information provided in the report is based on Australian Bureau of Statistics data for the total population of NSW of 6,984,172 as of 30 June 2008 (NSW Centre for Road Safety). The total number of NSW licence holders (drivers only, excluding riders and combined riders/drivers) is 4,181,259 (NSW Centre for Road Safety).
The total crash rate for the NSW population was 61 crashes per 100,000 (proportion: 0.0061, 95% confidence interval (CI): 0.0061–0.0062). The car crash rate for the NSW-licenced drivers was 91 per 100,000 (proportion: 0.0091, 95% CI: 0.0090–0.0092).
The single major, at-fault accident reported in the interviews gives the sample a crash rate of 222 per 100,000 (proportion: 0.0222, 95% CI: 0.0039–0.1157). The small sample size contributes to the wide confidence interval. The point estimate is higher than that for the total crash rate for the NSW population, and the car crash rate for NSW-licenced drivers, however, the CI is consistent with these estimates.
The average time following the assessment that non-driving respondents ceased driving was 4.6 months, with a range from 0 to 12 months. Three of these subjects did not return to driving after a successful assessment. The fourth subject ceased driving 11 months after the assessment, and the fifth subject ceased driving 12 months following the assessment. The average age of the respondents who had ceased driving was 64 years, with a range of 53–72 years.
None of these five participants had been involved in an accident prior to ceasing driving. Most had a current licence which they used for identification purposes. All the respondents reported stopping of their own accord, with one client discussing their concerns with their doctor who then cancelled their licence.
This study suggests that most people who pass a multi-disciplinary driver assessment after stroke continue driving safely and confidently in the medium to long term.
The 45 respondents interviewed provided a representative sample of the general stroke population when examined on the basis of gender and age. The proportion of men in the sample (64%) is higher than the estimated proportion of people with stroke who are men by the Australian Institute of Health and Welfare (2004) (58%), but consistent with the proportion of men assessed by the driver assessment centre (62%) in this study in 1999. The distribution of age in this study is similar to the 2007–2008 ABS National Health Survey data for individuals with stroke (Australian Bureau of Statistics, 2009).
The criteria for ‘safe’ driving, based on accidents and incidents, were met by 95% of the drivers in the sample. In addition, no significant difference was found in accident rates between drivers following stroke and the NSW population. These results are consistent with other literature in the area, including Katz et al. (1990), Schanke et al. (2008) and Finestone et al. (2009). Despite the small sample sizes and limited statistical analysis possible for each of these previous studies, this retrospective cohort study contributes to the growing body of evidence that drivers who successfully pass a multi-disciplinary driver assessment can be as safe as the general population.
For the purpose of this study the more complex driving conditions of driving at night, driving alone, driving distance and regularity and driving on highways or freeways, were used to identify those drivers who were confident in their driving (Galski, Ehle & Williams, 1998). People who did not drive in one or more of these conditions gave a number of reasons for not doing so, including lack of confidence. The high proportion of people driving in all five conditions (62.5%) or four or more conditions (82.5%) indicates that a multi-disciplinary driving assessment is able to identify people post-stroke who are capable of being confident driving in a variety of conditions.
Those stroke patients who do limit their driving in certain conditions may do so as a compensatory strategy. Research suggests that the use of compensatory strategies such as not driving at night, not driving alone and limiting driving distance and time can increase the level of safety of less competent older drivers to that of safe drivers who drive in all conditions (De Raedt & Ponjaert-Kristoffersen, 2000). This study supports the idea that compensatory strategies are also used by individuals following stroke, and these may contribute to the confidence and safety of these drivers. This finding is consistent with those of Schanke et al. (2008) who reported most patients changing driving patterns from pre-stroke driving, and Finestone et al. (2009) who found that over one-third of post-stroke drivers reported using compensatory strategies. It may be that education in the use of compensatory techniques and the increased use of driving restrictions may increase the number of people able to safely and confidently return to driving following stroke.
The perception of the people surveyed indicated that 80% felt safe when driving, and eight respondents believed that they were more defensive in their driving since completing the assessment. When considering those who had returned to driving but had been involved in an accident or incident, it is possible that the focus in this study on offensive driving has overlooked the importance of defensive driving. Although there was only one major ‘at fault’ accident described, it is difficult to determine whether there is a greater than average number of not at-fault accidents, or minor incidences experienced, given the difficulty in obtaining data on this phenomenon. It is also possible that dangerous drivers may feel themselves to be safe when driving (Heikkila et al., 1999).
Methodologically, the small sample, partially because of the response rate, may reduce the generalisability of these results. However, larger samples are difficult to obtain because of the small population available through driver assessment centres in Australia. The use of self-report may have introduced bias into the results, as individuals may under-report incidents and accidents owing to fear of losing their licence. Given that the comparative data for the NSW general population was collected through standardised reporting, this bias is not consistent in both groups, and so would lead to a higher number of accidents in the post-stroke group not being identified. This bias was minimised by having respondents describe the conditions in which they drove, as well as to rate their own driving ability. Finally, while this study supports the use of a multi-disciplinary driver assessment to identify drivers following stroke who can be safe and confident on the road, the retrospective design means it is not able to identify which components of the comprehensive assessment contribute most significantly to its success.
Despite these limitations in the methodology, this is one of the few studies to have examined the outcomes of individuals following stroke who have successfully passed a driver assessment. It provides the first examination of driving confidence in Australian post-stroke drivers. It also contributes to the small amount known of driving safety and accident rates in those returning to driving following stroke in Australia. Although a significant amount of further research is required, this study provides evidence for the ongoing use of multi-disciplinary driving assessments following stroke.
Driving is a valued role within the community, but carries with it a responsibility of safe driving, both offensive and defensive. It is important that driver-trained occupational therapists are accurately able to assess a person’s ability to return to safe driving. This follow-up of 45 respondents post-stroke who have successfully completed a comprehensive, multi-disciplinary driver assessment suggests that a successful assessment is able to identify those with the ability to drive safely and confidently in the medium to long term.
Financial support was received through Royal Rehabilitation Centre Sydney Clinical Care Review Committee and Quality Council Quality Improvement Grant 2000/2001 ($3000). No potential conflicts of interest have been identified for any authors. The authors would like to acknowledge the contribution of Annie McClusky (Post-Doctoral Research Fellow, University of Sydney) to this work.