Are you the sort of driver who occasionally goes a bit too fast?

If we’re being honest, most of us exceed the speed limit every now and then. We might be running late, distracted by the kids, allowing ourselves to have a bit of fun on a quiet, open road, or any of a million different reasons. I’ll hold my hands up and say that I’ve done all these things and more in my time.

Recently, I got caught for speeding on the M40. I’m not proud. It happened. It happens to a lot of drivers. According to DVLA data 2.3 million (about 5%) of the UK’s 46 million licence holders have points for speeding – and that excludes those who have not been caught, whose penalties have expired or who have chosen to undertake some form of educational training in lieu of points.

I was one of those who opted to take a half-day ‘speed awareness’ course. Yeah, I know. Four hours of grudgingly sitting in a room with a group of strangers drinking bad coffee where we get told that we should all stick to the speed limit, wave through tailgaters with a smile and generally take a chill pill before we head off on our merry ways once again.

Only it wasn’t like that. I actually learned a thing or two that made me sit up and take notice. I thought I’d share them here.

The perils of marginal speeding

I’ve mellowed a lot as a driver in recent years, particularly since the kids came along. I guess most of us – who may have been a little hot-headed in our younger years – grow up and calm down with age and the growing awareness of wanting to protect both our children and other people’s.

The typical person who attends this type of course has been caught doing, say, 35mph in a 30mph zone, or perhaps been nabbed near a point where the speed limit changes. We’re not talking about boy racers in hot hatches. Most of the offenders on the course I attended were 40-plus, professional-looking people who aren’t in the habit of imitating Formula 1 drivers.

Having said that, while it’s easy to appreciate the stupidity of driving everywhere at 100mph, like many people I’ve never fully thought through the potential effect of exceeding the speed limit by just a few miles per hour. Doing 35mph in a 30 zone can’t hurt much, right? But the risk in a potential accident is not about the speed you drive at but the speed you’re doing on impact.

Here’s an example.

At 30mph, the Highway Code says it takes 75 feet (23 metres) to brake a car to a standstill (and that’s before you add the distance covered while you react to the danger in the first place). For a modern, lightweight car with anti-lock braking and other gizmos it’s a bit less, but this video shows what a difference a small increase in speed makes.

In essence, the facts are as follows:

• A car initially travelling at 30mph brakes just in time to avoid an accident with a pedestrian. But over the same distance …
• Starting from 32mph, the car hits the pedestrian at 11mph – that’s about the same speed as a good marathon runner, only it’s a ton-plus of metal rather than Mo Farah.
• From 35mph, the impact speed is 18mph.
• From 40mph, this rises to 26mph.

So, in a situation where travelling at 30mph avoids an accident altogether, a rise in speed from 32 to 40mph – a 25% uplift – results in a 136% increase in impact speed.* That’s a lot, potentially the difference between an accident where a pedestrian suffers bumps and bruises and one which results in broken bones. Or worse.

That’s as much as they told us on the course. It’s only half the story, though.

The energy generated in a crash does not increase in proportion to speed. Physicists will tell you that the relationship between kinetic energy (KE), mass (m) and velocity (v) is governed by the equation KE=½mv².

In simple terms, our 25% increase in speed from 32 to 40mph more than doubles the impact speed and generates over five times the amount of energy. That’s energy that passes through the point of impact, some of which is dissipated through the car itself but much of it is transferred directly through whatever – or whoever – it hits.

Long story short: small change in speed, big change in the probability of a life-changing injury or death.

On average, five road users are killed every day in Britain and another ten suffer life-changing injuries. Speed is a contributing factor to around one in four road accidents – more than any other cause.

Eye-opening? Jaw-dropping? It was to me, and I’m from a scientific background where the maths should have been obvious to me.

I’m a rational person with three young children. These facts are inescapable. Now I’d be lying if I said was 100% certain this will lead to a permanent change in my speed but it has so far. It’s the sort of thing that makes me wish that all drivers – not just those who have been caught speeding – were made to work through and really understand the implications of this data. If it did, our roads would probably be a safer place for us and our children. I’d like that.

Here endeth the sermon.

* In reality, the differential is even bigger as the distance you will have covered in reacting to the danger will, of course, be greater at the higher speed, which further reduces available braking distance and increases the impact speed.

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