Updated 07 July 2014

Blood pressure, driver fitness and safe driving

How does blood pressure impact on driver fitness and why is maintaining a healthy blood pressure important for safe driving?

In some crash reports we are informed that the driver lost control of his vehicle after suffering "a medical episode". This most often includes having suffered a heart attack, stroke and fainting. In this section we would like to investigate how blood pressure impacts on driver fitness and why maintaining a healthy blood pressure is important for safe driving.

Normal levels of blood pressure are particularly important for the efficient function of vital organs such as the heart, brain and kidneys and for overall health and wellbeing. Not only is blood pressure an important consideration for drivers, but also the recommended medication and possible side effects thereof.

Blood pressure medication and driver fitness

It is generally accepted that while high blood pressure (hypertension) can lead to heart attacks and strokes, low blood pressure (hypotension) can cause dizziness, blurred vision and confusion. All of these are dangerous conditions when focus is needed in dangerous activities such driving a motor vehicle.

All adults should know their blood pressure level and should also find out if a close relative had or has hypertension (high blood pressure) as this could place them at increased risk.

There is medication available to treat both high and low blood pressure. Drivers who are aware of their abnormal blood pressure and who are using prescription medication should always be alert to the side effects of medication.

According to the New Mexico Department of Health, certain drugs can interfere with factors that are essential for safe driving, such as:
  • Coordination – needed for steering, braking, accelerating, and manipulating the vehicle;
  • Reaction time – needed to respond in time and appropriately deal with certain situations;
  • Judgment – helps with risk assessment, avoidance of hazards, and emergency decision-making;
  • Tracking – helps to stay in the lane and maintain the correct distance from other cars and obstacles;
  • Attention – ability to handle the high demand for information-processing;
  • Perception – needed for glare resistance, dark and light adaptation, and dynamic visual acuity.
The reactions caused by certain types of medication may include nausea, drowsiness, blurred vision, inability to think clearly, reduced cordination and diminished motor or judgment skills and can therefore impair your ability to drive.  These medications include over-the-counter medication as well as scheduled medication, prescribed by the doctor.

Blood pressure and your ability to drive

High blood pressure has few symptoms and it should not affect your ability to drive. However, you should not drive if your medicines cause symptoms which affect your driving ability. If this happens, ask your doctor if he or she can change your medicines to prevent the symptoms.

Women need to have their blood pressure checked regularly throughout pregnancy, whether they have high blood pressure or not. Blood pressure usually falls in the first few months of pregnancy, even in women who have been diagnosed with high blood pressure.

High blood pressure can develop for the first time in pregnancy – a condition called "pregnancy-induced hypertension". This may lead to a more serious condition called pre-eclampsia, which needs treatment with bed rest and drugs.

Blood pressure usually returns to normal after the pregnancy and the problem may not happen again in future pregnancies.

Professional drivers, blood pressure and disclosure

If you have high blood pressure then you should be able to drive a car or a motorcycle for personal use with no problem. There are however important considerations for professional drivers in many countries across the globe.

The medical standards for driving buses and large trucks and buses are much higher than for those driving a car or motorcycle. This is because the vehicles are much larger and heavier and because you may spend much more time behind the wheel, especially if driving is part of your job.

Commercial motor vehicle drivers have a greater propensity to develop hypertension than their peers in other professions. As the years of experience rise, part of the increase in hypertension may relate to accompanying aging, increase in body mass, or decline in physical activity.

If you have a licence to drive a large goods vehicle or passenger-carrying vehicle you will need to inform the traffic authorities if your blood pressure and medicines cause side-effects (problems) that could interfere with your ability to drive.

You may need to stop driving, find a different medicine and apply to renew your licence once your high blood pressure is under control. For example, beta-blocker medicines may cause you to feel dizzy or tired and if this happens to you, you may not be able to drive and, with your doctor's help, you will need to find another medicine.

If your resting blood pressure is consistently 180mmHg systolic (top or maximum number) or more and/or 100mmHg diastolic (bottom or minimum number) or more then you should not drive a bus or large truck. The good news is that once your blood pressure has been lowered and is under control, you can then be re-licensed.

(This medical standard usually also applies to driving a taxi, manning a boat or ship with passengers or flying an aircraft with passenger.)

Blood pressure and car insurance

Not only does the licensed driver have to disclose any hypertension or blackouts to the licensing authorities – the driver also needs to consider the vehicle insurance contract. A history of hypertension or blackouts will be deemed a material fact. If after an accident it appears that there has been a prior history of blackouts or hypertension that has not been disclosed such failure to disclose may be regarded as a breach of contract.


Driver error is blamed for approximately 85% of fatal road crashes in South Africa. The healthier the driver the better he/she will be equipped to remain focused, alert and able to reduce these driver errors or the threat of suffering "a medical episode".

 - (Article from Arrive Alive South Africa

(Photo of family in car from Shutterstock)


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Hypertension expert

Dr Jacomien de Villiers qualified as a specialist physician at the University of Pretoria in 1995. She worked at various clinics at the Department of Internal Medicine, Steve Biko Hospital, these include General Internal Medicine, Hypertension, Diabetes and Cardiology. She has run a private practice since 2001, as well as a consultant post at the Endocrine Clinic of Steve Biko Hospital.

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