Excessive heat directly affects the driver, causing fatigue, drowsiness and a noticeable loss of concentration. F. P.

Traffic

Driving in extreme heat can be as dangerous as driving under the influence of alcohol

The Spanish traffic authority reminds the public that heat reduces reflexes and concentration and increases the risk of accidents

Patxi Fernández

Madrid

Friday, 22 August 2025, 11:40

In the midst of one of the most intense heatwaves, with forecasts that could set a new record in some areas of Spain, the traffic directorate-general (DGT) issued a serious warning: driving in extreme heat can be as dangerous as driving under the influence of alcohol. The combination of both factors significantly increases the risk of accidents.

Excessive heat directly affects the driver, causing fatigue, drowsiness and a noticeable loss of concentration that lengthens the reaction time to unforeseen circumstances. According to some studies, this risk of accidents can increase by up to 20%.

In addition, heat adversely affects vision and can reduce the ability to see road signs by 10-20% when the temperature exceeds 35C. The The Royal Automobile Club of Spain (RACE) stresses that an inadequate cabin temperature puts both the driver and the other occupants at risk. The normal temperature inside the vehicle should be 21-23C.

Heatstroke is the most serious condition caused by overheating, which occurs when the body is unable to regulate its own temperature, which eventually exceeds 40C. Heatstrokes are mainly caused by prolonged exposure to high temperatures or intense physical activity in a hot and humid environment.

When you suffer from a heatstroke, your body stops sweating, which prevents it from cooling down naturally. This can damage vital organs such as the brain, heart and kidneys, and in severe cases, can be fatal.

DGT and RACE recommendations for a safe journey

Prepare the vehicle: High temperatures can make it easier for maintenance deficiencies to occur. It is essential to check fluid levels and the condition of different car parts, such as tyres, which wear up to 25% more in the summer.

Avoid peak hours: Schedule trips outside the period between 1pm and 5pm, when temperatures are at their highest.

Hydrate and rest: Drinking water frequently, without waiting until you are thirsty, is crucial to avoid dehydration. Stop every two hours or every 200 kilometres to rest. Fatigue and drowsiness are behind 7% of road accidents.

Adjust the vehicle: Before starting, the windows should be lowered to air out the passenger compartment. Once the vehicle has been started, the air conditioning should be kept between 22C and 24C to avoid sudden temperature changes.

Be careful with alcohol consumption: The DGT insists on not consuming even a drop of alcohol before driving, as its effects multiply in the heat, increasing dehydration and raising the risk of heatstrokes.

Driving under the effects of heat is extremely dangerous, as it directly affects the driver's physical and mental capabilities, which significantly increases the risk of accidents. The symptoms may be mistaken for fatigue or dehydration, but the effects are much more serious.

Excessive heat reduces the driver's attention and ability to react. This can lead to poor decision-making or slower reaction times to unexpected events. Heat can cause confusion, dizziness, irritability and aggressiveness. These behavioural changes are incompatible with safe and cautious driving.

High temperatures can cause a feeling of extreme exhaustion and sudden drowsiness, increasing the risk of falling asleep at the wheel. In addition, heat can cause eye fatigue, blurred vision and glare, reducing visibility.

How does heat affect the car

Heat affects not only people, but also the vehicle. High temperatures can reduce engine power, increase fuel consumption and tyre wear and affect battery and braking system performance.

In addition, there is a serious and recurrent risk in the summer: children and pets being left inside the car. The Spanish association of out-of-hospital paediatrics and primary care (Sepeap) reminds the public that on a day of 36C, the temperature inside a car can reach 67C in just 15 minutes, with fatal consequences.

Devices and apps such as Waze's child reminder or EvenFlo's sensor safe are useful, as they alert the driver to the presence of a child in the back seat to prevent fatal incidents.