Please be advised to check with your countries’ driving licence authorities for directive on Parkinson’s disease (PD) and fitness to drive, since many countries have different guidelines. It should be noted that PD may co-occur with comorbidities that may also impact fitness to drive.  
 
Also note that the diagnosis of PD may not show up in all countries’ fitness to drive regulations. This does not however imply that there will be no impact on fitness to drive for these patients. Consequences might arise from the comorbidities or from the functional consequences resulting from the disease.  
 
In the UK, the Driver and Vehicle Licensing Agency (DVLA) guide for medical professionals1 states that people with a Group 1 licence (car and motorcycle) who have PD may be able to drive but must notify the DVLA. People with a Group 2 licence (bus and lorry) must not drive and must notify the DVLA.  
 
In France, the decree of March 28, 2022 establishing the list of medical conditions that are incompatible or compatible with driving states that people with a Group 1 licence (car and motorcycle) who have PD can no longer drive if they suffer from a slight cognitive decline (assessed by the Reisberg scale, stage 3) (Arrêté du 28 mars 2022 modifiant l’arrêté du 31 juillet 2012 relatif à l’organisation du contrôle medical de l’aptitude à la conduit, 2022
 
In Belgium, the Annex 6 of the Royal Decree on Driving Licences (1998) does not specifically mention PD as a contra-indication for fitness to drive. It is however specified that all functional impairments on locomotor, cognitive, and visual level need to be assessed by a dedicated evaluation centre. The norms used for group 1 and group 2 licences are different. The standards to be achieved are stricter for Group 2 licences. 

Parkinson’s disease is a progressive neurological condition that starts with cell death of a small area deep in the brain, the substantia nigra. The substantia nigra produces dopamine. Dopamine is very important for sending signals from one part of the brain to the other. PD will gradually affect other parts of the brain. The symptoms vary greatly amongst individuals, and can affect motor functions, cognition, vision, and behavior. Common motor symptoms are shaking (tremor), muscle stiffness (rigidity), slow movements (bradykinesia), and balance and gait problems. Vision symptoms include difficulties with discerning subtle differences in shades (contrast sensitivity), color discrimination, double vision, and reduced blinking of the eyes. Cognitive symptoms include difficulties with executive functions (e.g., problem solving, multitasking, dividing attention, and working memory), speed of information processing, and visual spatial processing. These cognitive changes can be mild at first but may develop in some cases to PD dementia. Changes in behavior such as depression and anxiety are also common in PD.  

Parkinson’s disease is a neurodegenerative disease that will eventually affect the fitness to drive. A diagnosis of PD does not necessarily lead to loss of driving privileges. It is possible that some people with PD may continue to drive safely long after diagnosis. 
 
Driving tends to be the safest in the early stages. With the steady decline of skills over time, drivers with PD may limit their driving, avoiding traffic situations that they no longer feel comfortable driving in. Drivers with PD tend to gradually stop driving at night or during inclement weather, during peak hour traffic, avoid highways, or restrict their driving to familiar areas. Sometimes drivers with PD are less aware of changes in driving skills and this can affect their ability to self- regulate their driving. 
 
All drivers with PD will eventually retire from driving and become dependent on others for their mobility needs such as shopping, visiting doctors, friends, families or hospital visits. Adequate planning for driving retirement should therefore start at diagnosis and continue to be discussed in the household or caring environment, and with the health care team throughout the disease progression. This type of support may assist drivers with PD to accept driving cessation. 
 
While some licensing authorities request drivers to disclose changes in medical conditions and monitor the fitness to drive over time, others expect the health care team (often the physician) to report medical conditions that may jeopardize safe driving to the licensing authorities.  
 
Below are some indicators to look out for: 
 
Potential reported ‘red flags’ for drivers with PD to be aware of are changes in driving behaviour such as: 

• Any ‘at fault’ car crashes or near misses  
• Blurred vision during driving 
• Difficulty anticipating and response to traffic events 
• Difficulty driving while conversing or while listening to the radio 
• Difficulty moving leg freely between the accelerator and brake pedals 
• Difficulty remembering where the car key is 
• Dings, scrapes, and scratches on the car bumper 
• Delayed reactions to, or poor judgement of, road situations 
• Drive at inappropriate speed (too fast or too slow) 
• Fail to observe road signs and traffic lights 
• Get lost along a familiar route 
• Get confused between the accelerator and brake pedals 
• Multiple traffic violations in short time span 
• Passengers do not feel safe riding along 
• Passengers becoming actively involved in managing operational aspects of the journey (‘co-piloting’ e.g. pointing out hazards or traffic light changes) 
• Parking problems / hitting curbs 
• Stop abruptly 
• Veer off the lane 

The presence of other symptoms that may affect driving ability in PD should be considered, for example:

• Unpredictable motor fluctuations 
• Deep brain stimulator implants 
• Changes in medication intake 
• Medication side effects (involuntary muscle contractions (dystonia); involuntary movements (hyperkinesia), sleepiness, blurred vision, confusion) 
• Changes in personality with disinhibition, impulsivity, addiction and / or aggression 
• Lack of disease insight 
• Excessive daytime sleepiness and variations in arousal 
• Psychotic symptoms such as hallucinations or delusions 
• Severe anxiety and / or depression 
 
Adherence to the prescribed medication plan is paramount for safe driving. Patients and the health care team should be able to determine ON/OFF medication effects on fitness to drive and plan driving according to the patients’ functional status. 

Parkinson’s disease is associated with a high risk of other co-morbidities, some of which are related to ageing and others that are directly related to PD, for example: 

• Sensory deficits e.g. visual and hearing impairment 
• Physical impairment e.g. osteoarthritis, pain, deconditioning 
• Effects of concomitant drugs e.g. benzodiazepines, opiates and anticholinergic medications 

 It should be recognised that a number of ‘lower level’ deficits such as loss of muscle strength, sensory deficits or other impairments, that alone would not be sufficient to raise concerns but in combination may make a person’s driving unsafe^2.  

Motor symptoms such as tremor, bradykinesia, and impaired balance are usually observed during rest and while performing activities. Muscle stiffness can be felt while moving the arms and legs. Motor symptoms are more apparent when stressed or performing two tasks at the same time. One typical PD symptom is freezing of gait, where the feet feel glued to the floor when (attempting to) walk. Although debilitating while walking, in most cases freezing does not occur once seated and driving. Motor symptoms are usually the reason patients go see a doctor, but on their own are not the reason to stop driving.   

Although visual acuity and visual field are the only explicitly mentioned visual criteria in most countries’ fitness to drive standards, impaired contrast sensitivity is one of the main visual sensory symptoms affecting driving in PD³ However, in most countries “Contrast sensitivity may not be under the fitness to drive standards for vision. To a lesser extent, color discrimination may also affect driving. Some patients with PD report blurred vision which is a red flag for driving.  

Vision can be assessed by qualified professionals such as ophthalmologists, optometrists, basic vision screening can be carried out by the fitness to drive expert.   

Vision is usually assessed with instrumented vision apparatus, but charts (e.g., Snellen Acuity Chart) are also useful. The Pelli-Robson contrast sensitivity chart is frequently used for assessing contrast sensitivity.  

Patients with PD may show symptoms of cognitive impairment even at diagnosis. About 25% of patients have mild cognitive impairment at diagnosis⁴. Even mild cognitive impairment may affect the ability to drive⁵. Parkinson’s disease dementia in combination with motor and visual symptoms is a red flag for driving continuation.    

No single cognitive test can predict fitness to drive in PD³. The results of cognitive tests may indicate who needs a fitness to drive assessment and may highlight areas of weakness that need to be evaluated in a formal on-road test⁶.  

There may be a cost associated with the use of these instruments or training in their use. Commonly used cognitive screening tests include the Montreal Cognitive Assessment (MoCA), Trail Making Test A and B, Stroop Color Word Test, Rey Osterrieth Complex Figure, and Useful Field of View⁵. These instruments provide an initial picture of one or more cognitive domains.  

There are no specific vehicle control modifications for the symptoms of PD, although it is recommended to transition to automated gearbox and power steering, these adaptations may assist drivers to drive safely as long as clinical symptoms remain manageable. Additional aids can be installed to help patients transfer in and out of the car, such as a HandyBar or swivel seat. Seat belt extenders can be used to help locking in the seat belt. 

Drivers with PD may have difficulties with all aspects of driving. Basic operational driving skills such as steering, pedaling and lane positioning can be impaired. Higher order driving skills such as speed adaptations, driving on highways, navigating intersections and roundabouts can also be impaired⁶. Motor symptoms that were apparent during clinical assessment should be observed while driving for their impact on fitness to drive.

Drivers with PD are mostly well aware of their limitations and make appropriate adjustments to their driving (self-regulation). When buying a new car, drivers with PD should opt for a car with automatic transmission, high seating, and large windows.

When the automatic gearbox is a condition of fitness to drive, it would be coded as 10.02.  

All fairly recent cars have sufficient steering enforcement to accommodate most loss of strength. If this standard steering enforcement proves to be insufficient a driving assessor or other specialist would measure the force available by the driver (in Newton). This force would then be coded on the driving licence as code 40.01 (??N). In some countries apparatus to measure this force is lacking. They limit themselves to indicating that there should be additional steering enforcement by indicating code 40.01 (-N). It is then up to the technicians to set the power steering so that the steering wheel can be turned smoothly and efficiently in all turning positions. Too much steering enforcement can also make efficient steering impossible.    

Patient resources:  

Driving | Parkinson’s Foundation  

Decisions About Driving for Persons with Neurodegenerative Conditions – Archives of Physical Medicine and Rehabilitation (archives-pmr.org)  

Arrêté du 28 mars 2022 modifiant l’arrêté du 31 juillet 2012 relatif à l’organisation du contrôle médical de l’aptitude à la conduite, Pub. L. No. 28, NOR : INTS2208151A 27 (2022). https://www.legifrance.gouv.fr/eli/arrete/2022/3/28/INTS2208151A/jo/texte  

References

1. Driver Vehicle Licensing Agency. Assessing fitness to drive: a guide for medical professionals. Department for Transport; 2018.  

2. Ranchet M, Tant M, Akinwuntan AE, Neal E, Devos H. Comorbidity in Drivers with Parkinson’s Disease. J Am Geriatr Soc. Feb 2016;64(2):342-6. doi:10.1111/jgs.13942  

3. Devos H, Vandenberghe W, Nieuwboer A, Tant M, Baten G, De Weerdt W. Predictors of fitness to drive in people with Parkinson disease. Neurology. Oct 2 2007;69(14):1434-41. doi:10.1212/01.wnl.0000277640.58685.fc  

4. Aarsland D, Batzu L, Halliday GM, et al. Parkinson disease-associated cognitive impairment. Nat Rev Dis Primers. Jul 1 2021;7(1):47. doi:10.1038/s41572-021-00280-3  

5. Ranchet M, Devos H, Uc EY. Driving in Parkinson Disease. Clin Geriatr Med. Feb 2020;36(1):141-148. doi:10.1016/j.cger.2019.09.007  

6. Devos H, Vandenberghe W, Tant M, et al. Driving and off-road impairments underlying failure on road testing in Parkinson’s disease. Mov Disord. Dec 2013;28(14):1949-56. doi:10.1002/mds.25701  

Hannes Devos, University of Kansas Medical Center, Kansas City, KS 

Maud Ranchet, Universitè Gustave Eiffel, Lyon, France 

Mark Tant, Vias Institute, Brussels, Belgium