How to remember stopping distances for the Highway Code

The Highway Code makes you learn this complicated table by rote. But it’s significantly less effort to learn the following formulas:

\[ \begin{aligned} s(n) &= \text{stopping distance at } 10n \text{ mph} \\ t(n) &= \text{thinking distance at } 10n \text{ mph} \\ b(n) &= \text{braking distance at } 10n \text{ mph} \\ s(n) &= t(n) + b(n) \\ t(n) &= 3n \text{ meters} \\ b(n) &= \frac{3n^2 + n}{2} - 1 \text{ meters} \\ \end{aligned} \]

Working through one example, stopping at 60 mph:

\[ \begin{aligned} \text{stopping distance at } 60 \text{ mph} &= s(6) \\ &= t(6) + b(6) \\ &= 18 \text{ meters} + 56 \text{ meters} \\ &= 74 \text{ meters} \\ t(6) &= 3 \times 6 = 18 \text{ meters} \\ b(6) &= \frac{3 \times 6^2 + 6}{2} - 1 = 56 \text{ meters} \\ \end{aligned} \]

The answer is off by one meter in some cases. But the theory test is multiple-choice, so just pick the answer that’s closest.

Tagged .
👋 I'm Jim, a full-stack product engineer. Want to build an amazing product and a profitable business? Read more about me or Get in touch!

More by Jim

This page copyright James Fisher 2019. Content is not associated with my employer. Found an error? Edit this page.