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Will Driving Faster Really Get You There Quicker?

(Warning – contains maths!)

It seems ingrained in our human mentality.  If you go faster, you get there more quickly, right? After all, we’ve all seen this in childhood.  When you walked to school, let’s say it usually took you 15 minutes. I am possibly showing my age here with the assumption that you walked 15 minutes to school – although a 15-minute walk is pretty reasonable and there’s no reason why kids these days (that’s really showing my age) can’t do it as well.  Anyway, back to the topic.  When you were a kid walking to school, if you realized that you’d forgotten your homework and had to double back for it, you pretty soon found out that if you jogged or ran, you’d still make it to the school gate before the bell rang.

When we grew up and got cars, we applied the same logic. If we overslept the alarm or had some sort of household emergency before setting off to work, we believe that if we step on the accelerator a little bit harder, we’ll make up for lost time.  Or will we?

We’ll leave aside the issue that speeding is illegal and that you will get pinged for it if you get caught.  Yes, that means you, even if you’re going only a teeny weeny 10 km/h over the legal limit.  Let’s do the maths instead.

Let’s say your commute takes about 30 minutes and you usually drive at 50 km/h, which is the signed speed limit on the road you take.  This means that, at least on paper, you’re covering about 25 km.  The equation is Distance (in km) ÷ Your Speed (in km/h) = Travel Time (in hours).  What happens if we plug your sneaky wee attempt at speeding into this equation, with the assumption that you’re going to try driving to work at 60 km/h to make up the time spent cleaning up after the cat had vomited in the middle of the living room?  We’ve got 25 ÷ 60 = 0.416667.  To turn 0.416667 hours into the equivalent in minutes, multiply it by 60 and you get (drum roll; the smart cookies reading this will have already clicked) 25 minutes.  So what you’ve saved – in theory – by speeding 10 km/h faster is 5 minutes.  Which isn’t much.

Of course, your average travel speed probably never was your target speed, whether that was 50 km/h or 60 km/h.  We all know that in peak travel hours, you have to slow down at intersections, wait at Give Way signs, wait at pedestrian crossings for the kids who are walking to school and wait at traffic lights. This means that the amount of your journey spent actually going faster will only be a few minutes out of your commute, so you won’t actually be saving 5 minutes at all. You’ll be saving more like 1 or 2 minutes and you will end up being late for work – and you’ll probably try blaming it on the traffic rather than that cat.

However, while you’ve been pressing down the accelerator in that attempt to get to work on time, you’ve been revving your engine that little bit harder, and you’ve probably had to brake harder.  That extra bit of accelerator means more fuel consumption – or more drain on the battery, so those of you with EVs can wipe that smug smile off your faces because this applies across the board.  That extra stress on the brake also means more wear and tear, so in the long run, although you may have saved a couple of minutes on your commute, you’ll have put a bit more on your fuel bill and/or your maintenance bill.  You have to ask yourself if it’s really worth it.

So why did travelling faster work so well when you were a kid running to school instead of walking after forgetting your homework?  And is there ever a time when going faster will actually get you there quicker.

Let’s start with that first question.  When you were a kid walking to school, you probably went there more or less non-stop, with maybe the odd pause if you had to cross the road.  Walking speed varies by age and sex, but let’s say that you could walk at about 3 km/h.  A child’s maximum running speed at the age of 2 is about 9 km/h but you were older than that if you were walking to school and you probably weren’t running at your maximum, so we’ll say that your running to school speed was about 6 km/h.  This is double your walking speed (a 100% increase), whereas increasing your driving speed from 50 km/h to 60 km/h is a 20% increase.

Lastly, is there ever a time when going faster helps you make up lost time? The answer is probably yes, but only if (a) you’re covering a long distance so small changes add up and (b) your route is free-flowing without need to stop or slow down for significant portions of the time.  Think rural roads and well-designed motorways.  Even then, your gain in time won’t be all that much.  Perhaps, on a rural road, you might be able to shave 5 minutes off what would have been a 20-min trip by travelling at an average speed of 100 km/h rather than the average of 80 km/h.  Longer trips will get more savings in time but this may be off-set by increased fuel consumption – and it’s up to you if you think this is worth it!

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