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Question

Difficulty: MediumStopping Distances

A car is travelling at the national speed limit of 70 mph70\text{ mph} (112 km/h112\text{ km/h}) along a dry, level motorway in clear weather conditions. According to The Highway Code, what is the vehicle's total stopping distance in metres?

Answer: 96 metres

Answer

96 metres
According to The Highway Code, at a speed of 70 mph70\text{ mph} (112 km/h112\text{ km/h}) on a dry road, thinking distance is 21 metres21\text{ metres} (70 feet70\text{ feet}) and braking distance is 75 metres75\text{ metres} (245 feet245\text{ feet}). Adding these together gives an overall stopping distance of 96 metres96\text{ metres} (315 feet315\text{ feet}).

Step-by-Step Solution

1
Identify the thinking distance component at 70 mph70\text{ mph}
21 metres21\text{ metres}
The Highway Code establishes that at 70 mph70\text{ mph}, reaction/thinking distance is 21 metres21\text{ metres} (70 feet70\text{ feet}).
2
Identify the braking distance component at 70 mph70\text{ mph}
75 metres75\text{ metres}
Under dry, optimal road conditions, the distance travelled while braking from 70 mph70\text{ mph} to a complete stop is 75 metres75\text{ metres} (245 feet245\text{ feet}).
3
Calculate the total stopping distance by summing thinking and braking distances
21 metres+75 metres=96 metres21\text{ metres} + 75\text{ metres} = 96\text{ metres}
Total stopping distance is defined as the sum of thinking distance and braking distance.

Key Concept

Total Stopping Distance at 70 mph

Alternative Method

Convert from the standard imperial Highway Code value (315 feet315\text{ feet}) by using the standard conversion factor or direct component addition in feet (70 ft+245 ft=315 ft70\text{ ft} + 245\text{ ft} = 315\text{ ft}), which equates to 96 metres96\text{ metres}.
Estimated Time:1m 0s
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Topics

Stopping Distances

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