Excessive heat increases fatigue and reduces reflexes, causing slower reaction times and more errors. DGT

Driving in Extreme Heat as Dangerous as Driving Under the Influence

Patxi Fernández

Martes, 27 de mayo 2025, 14:20

Extreme heat takes a toll on drivers: it increases fatigue and reduces reflexes, leading to slower reaction times and more errors. According to some studies, the risk of accidents rises by up to 20% in high temperatures.

Additionally, heat impairs vision. When driving at 35°C, we miss between 10% and 20% of traffic signs. Excessive heat can also increase aggression and nervousness behind the wheel.

The DGT reminds us that heat affects vehicles too, as high temperatures make maintenance deficiencies more apparent. Therefore, it's advisable to check your vehicle before hitting the road, including parts and fluid levels.

Typically, the highest temperatures occur between 1:00 PM and 5:00 PM. The organisation also recommends stopping every two hours or every 200 kilometres at most, and to pull over if you feel any signs of fatigue while driving. Recent studies suggest that fatigue and drowsiness could be behind 7% of road accidents.

DGT Recommendations

Ventilate the vehicle: Before starting to drive, lower the car windows to ventilate the cabin and equalise the interior and exterior temperatures.

Air conditioning: If you turn on the air conditioning, lower the windows for the first few seconds to expel the hot air outside.

Temperature: Keep the air conditioning temperature between 22°C and 24°C to avoid chills from sudden temperature changes with the outside. Avoid directing the vents towards your face and chest.

Avoid the hottest hours: Plan your trips to avoid the hottest hours.

Comfortable clothing: Wear comfortable and loose clothing and shoes that properly support your feet.

Stay hydrated: Carry cool non-alcoholic drinks. Drink frequently, without waiting to feel thirsty. The best options are water or fruit juices. Do not consume any alcohol if you are going to drive: it reduces reflexes, creates a sense of euphoria and false security, even at the lowest levels.

Eating: It is advisable to eat a light diet, rich in proteins and vitamins, avoiding fatty foods.

Rest: Stop every 200 km or 2 hours to hydrate, ventilate the vehicle, and relax.

Fatigue: If at any time you detect symptoms of fatigue or drowsiness, stop immediately to rest or sleep.

Shade: During stops, try to park in shaded areas. If you stop in the sun, do not leave elderly people, children, or animals inside the vehicle.

Ensure the engine does not overheat. Monitor the vehicle's engine temperature.

Extreme heat can increase the likelihood of a traffic accident by up to 25%, as when the interior of the vehicle exceeds 35°C, the risk is comparable to driving under the influence of an alcohol level between 0.5 and 0.8 g/l, according to Euromaster data based on a report by the Road Safety Foundation (FESVIAL).

Therefore, keeping the car's air conditioning system in perfect condition is essential. It is recommended to perform two very simple tasks that ensure the cabin temperature is always optimal for safe driving: changing the cabin filter and recharging the air conditioning system's gas.

Cabin Filter: Why Change It

The cabin filter, which filters particles and pollutants from the outside air to ensure better air quality inside the vehicle, is an easy and economical task, costing approximately between 15 and 30 euros. Most manufacturers advise replacing it every 20,000 kilometres or when obstructions are detected, especially after spring when pollen and particles get trapped in the filter. A dirty filter can cause the air conditioning to operate at lower efficiency or barely function.

The most evident symptom indicating the need to change the cabin filter is the presence of bad odours when activating the air or fan. Additionally, if the fan's airflow is weak or irregular, the filter is likely clogged with grease and particles, hindering its proper function. Manufacturers typically recommend changing it annually to maintain air quality and system performance.

Euromaster recommends replacing it annually, ideally between spring and summer. There are also various types of cabin filters, and the most recommended are those known as activated carbon filters, which can better mitigate allergies and prevent odours, promoting better air quality inside the vehicle.

Air Conditioning Gas Recharge: When Is It Necessary?

Another common cause of reduced performance in the air conditioning system is the depletion of the air conditioning gas, which can turn a long journey into an uncomfortable and unsafe experience. If a gas recharge is necessary—a task that can cost between 60 and 150 euros depending on the vehicle—workshop professionals will complete it in about half an hour.

However, there are clear symptoms indicating that the gas pressure in the air conditioning is insufficient and it is advisable to recharge the appropriate amount. To check its condition, you will need to turn on the air conditioning, and if no cold air comes out, it comes out with little power, or the air conditioning fails to defog the windows in cold weather (it also serves this function), you will need to recharge this gas.

It is recommended to maintain the interior temperature around 22 degrees, a figure that helps reduce risks and drive with greater safety and comfort during the hot days ahead.