Is it advisable to open windows on the motorway?

From an engineering perspective, open windows disrupt a car’s aerodynamics, creating turbulence that forces the engine to work harder. This is especially noticeable at motorway speeds, where drag increases exponentially. Tests show fuel consumption rises by 5-10% with windows down. For optimal efficiency, use climate control and keep windows shut.

It is not recommended to open windows on the motorway as it may pose safety hazards. Particularly when crossing bridges, where lateral winds are common, excessive speed combined with open windows could potentially cause a vehicle to overturn.

When windows are open, the increased wind resistance from air rushing into the cabin will hinder the vehicle's progress and significantly increase fuel consumption.

Hazards of opening windows on the motorway:

1. Increased risk of accidents

On motorways where the speed limit is 120 km/h, vehicles travel at considerable velocity. Fully opened windows allow turbulent air currents from all directions to enter the cabin, which may damage loose interior fittings or decorations. If any control buttons are not securely fixed, they could potentially be dislodged by the wind force, hence the recommendation against window opening.

Even with only one window open, occupants may experience considerable discomfort. The incoming airflow can impair the driver's visibility and potentially cause dizziness, creating dangerous driving conditions.

1. Increased fuel consumption

Open windows compromise the vehicle's aerodynamic integrity, disrupting its streamlined design. This substantially increases the frontal area exposed to air resistance - akin to towing a trailer behind the vehicle - resulting in markedly higher fuel consumption.

1. Trapped odours in the cabin

When attempting to ventilate unpleasant odours by opening windows on the same side of the vehicle, counterproductive air currents are created. This configuration not only fails to facilitate proper air circulation but actually traps odours within the cabin. Prolonged exposure to such conditions may cause passengers to experience nausea and dizziness.

Opening windows on the motorway is generally not advisable due to increased aerodynamic drag, reduced fuel efficiency, and higher noise levels. At speeds above 50 mph, the drag caused by open windows can decrease fuel economy by up to 10%, according to studies by the Society of Automotive Engineers. Additionally, wind noise becomes intrusive, making conversations difficult and increasing driver fatigue.

For comfort and efficiency, it’s better to use the car’s climate control system. Modern vehicles, like the Tesla Model 3 or BMW iX, have efficient air recirculation modes that maintain airflow without the drawbacks of open windows. If fresh air is needed, slightly cracking a single window is preferable to fully opening multiple windows.

Safety is another consideration. Open windows can allow debris or insects to enter the cabin unexpectedly. In rare cases, strong crosswinds may affect vehicle stability. For electric vehicles like the Nissan Leaf, preserving range is critical, and reducing aerodynamic drag by keeping windows closed helps maximise efficiency.

In summary, while occasional fresh air is fine, keeping windows closed on the motorway is the smarter choice for fuel economy, comfort, and safety.