According to The Official Highway Code, a car travelling at 30\text{ mph} (48\text{ km/h})… — UK Driving Theory Test

According to The Official Highway Code, a car travelling at $30\text{ mph}$ ( $48\text{ km/h}$ ) has a standard braking distance of $14\text{ metres}$ on a dry, level asphalt road. When driving on a road surface covered in compact snow or ice, reduced tyre grip can increase the braking distance by up to $10$ times. What is the vehicle's estimated braking distance, in metres, under these icy conditions?

Answer: 140 metres

Answer

140 metres

On icy or snow-covered roads, tyre friction is severely compromised, meaning braking distance alone can be up to ten times greater than on a dry road. Multiplying the standard

30\text{ mph}

braking distance of

14\text{ metres}

10

gives an estimated braking distance of

140\text{ metres}

Step-by-Step Solution

Identify the base braking distance under standard dry conditions

The braking distance at

30\text{ mph}

on dry tarmac is

14\text{ metres}

This is the baseline distance required for the vehicle's brakes and tyres to bring it to a complete halt from

30\text{ mph}

under normal friction levels

Identify the factor by which braking distance increases in icy conditions

Icy surfaces multiply braking distance by a factor of up to

10

Severely compromised tyre adhesion on ice drastically lowers frictional resistance between tyres and the road surface

Calculate the adjusted braking distance

14\text{ m} \times 10 = 140\text{ metres}

Multiplying the baseline braking distance by the weather multiplier yields the maximum expected braking distance on ice

Key Concept

Effect of icy road surfaces as a multiplier on vehicle braking distance

Estimated Time:1m 0s

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