In driving safety, hydroplaning (aquaplaning), where a vehicle's tyres ride on a thin layer of water and lose contact with the road, is usually caused mainly by which driver behaviour?

Introduction / Context:
Hydroplaning, also called aquaplaning, is a dangerous driving condition that occurs when a layer of water builds up between a vehicle's tyres and the road surface. When this happens, the tyres lose direct contact with the road and essentially skim across the water, leading to a loss of steering and braking control. Understanding what behaviours increase the risk of hydroplaning helps drivers adjust their speed and driving style during heavy rain or when water is pooled on the road. This question focuses on the main driver behaviour responsible for hydroplaning.

Given Data / Assumptions:

• Hydroplaning occurs when tyres ride on water rather than directly on the road.
• Water depth, tyre condition, and vehicle speed all influence the risk.
• The options compare high speed and normal, safe driving behaviours.
• We assume typical road and tyre conditions, not extreme racing or off-road situations.

Concept / Approach:
Tyres are designed with grooves (tread) to channel water away from the contact patch between the tyre and road. At moderate speeds and with adequate tread, water is pushed out from under the tyre. As speed increases, however, there is less time for water to be displaced. If the water layer is deep enough and the vehicle is travelling too fast, a wedge of water can build up under the tyre, lifting it off the road. Once this happens, friction drops dramatically, and the driver may feel the steering go light and unresponsive. This process is hydroplaning. Therefore, driving at excessive speed on a wet road is the primary behaviour that leads to hydroplaning.

Step-by-Step Solution:
Step 1: Recall that hydroplaning involves a loss of contact between the tyre and road due to water. Step 2: Understand that tyres need time and proper tread depth to push water away from the road surface. Step 3: Recognise that higher speeds reduce the time available for water displacement and increase the likelihood that water will build up under the tyres. Step 4: Compare this to gentle stops on a dry road and slow driving through shallow puddles, which do not typically cause hydroplaning. Step 5: Conclude that driving at excessive speed on a wet road is the main driver behaviour that causes hydroplaning.

Verification / Alternative check:
Traffic safety agencies and driving manuals emphasise lowering speed during heavy rain as one of the most important steps to prevent hydroplaning. They often provide specific advice such as reducing speed when water is visible on the road, avoiding sudden acceleration and braking, and maintaining good tyre tread. Studies and experiments show that hydroplaning tends to occur above certain speed thresholds depending on water depth and tyre condition. Normal-speed, cautious driving on wet roads with good tyres seldom leads to hydroplaning. This confirms that excessive speed on a wet surface is the key risk factor.

Why Other Options Are Wrong:
Making gentle, gradual stops on a dry road surface does not involve a significant water layer, so it does not cause hydroplaning.
Driving slowly through shallow puddles with good tread on the tyres allows water to be displaced effectively, greatly reducing the risk of hydroplaning.
Parking the vehicle with the handbrake applied on a flat surface has nothing to do with moving tyres on water and therefore cannot cause hydroplaning.

Common Pitfalls:
Drivers sometimes assume that modern tyres or anti-lock braking systems (ABS) can completely prevent hydroplaning, leading them to maintain higher speeds in the rain. This is a dangerous misconception; no system can overcome the basic physics of water depth and speed. Another mistake is focusing only on the presence of water and ignoring speed, when in fact both water and speed interact to create the risk. A simple rule is: the more water on the road, the slower you should drive. Remembering that excessive speed on wet roads is the main cause of hydroplaning helps you answer exam questions and drives safer in real life.

Final Answer:
Hydroplaning is usually caused primarily by Driving at excessive speed on a wet road so that the tyres cannot push water away fast enough.