The Motor Vehicles department (MVD) and police have warned motorists against speeding on national highways during the monsoon, citing the risk of aquaplaning.

Aquaplaning or hydroplaning is a phenomenon in which a vehicle’s tyres lose contact with the road due to a layer of water between the tyres and the surface. It happens when vehicles travel at high speed over roads covered by standing or flowing water.

The warning follows a series of fatal crashes on national highways in the State since the onset of the monsoon. In Malappuram district alone, five people were killed in two recent accidents — three at Thenhipalam on NH 66 and two at Kondotty on NH 966. Dozens were injured.

The authorities’ preliminary assessment points to aquaplaning caused by excessive speed on wet roads. Waterlogging has been reported on several stretches of the six-lane NH 66 after rainfall, with critics attributing it to flaws in the road’s design.

“Aquaplaning is dangerous because most drivers realise what it is only when they experience it. Even a few millimetres of water can trigger it at high speeds. Reducing speed during rain is the most effective safety measure,” said P.M. Mohammed Najeeb, traffic psychologist and former Deputy Transport Commissioner.

According to MVD officials, aquaplaning occurs when tyres are unable to disperse water fast enough, causing a vehicle to glide over a layer of water rather than the road surface. Drivers can lose steering and braking control instantly. Sudden braking may cause the vehicle to spin, overturn or collide with other vehicles.

Mr. Najeeb said driver training would be key to improving road safety. “Speeding is a habit. Drivers accustomed to speeding are unlikely to slow down when it rains, though driving conditions change completely in the rain,” he said.

The MVD has advised motorists to keep speeds below 60 kmph on wet roads and in areas with standing water. Officials also stressed the need for proper tyre maintenance, including adequate tread depth and correct air pressure.

“If aquaplaning occurs, drivers should keep the steering wheel steady, ease off the accelerator, avoid sudden braking or sharp steering inputs, and allow the vehicle to slow down until the tyres regain contact with the road,” said Mr. Najeeb.

The MVD also advised motorists to avoid driving through waterlogged stretches and not to speed through water accumulated along road shoulders.