Thursday, November 20, 2014

How fast do cars actually go?


I calculated the average speed that people achieve in cars, considering their actual average speed on the road, and the time they spend earning the money to maintain their cars. I found that, for an above-average income ($60000/year), a person driving 10000 km/year achieves an average speed of only 22.9 km/h. If you earn less than this, you must spend more time earning money to pay for your car, and your average speed is lower still.

How fast to cars go?

What I want to do in this article, is work out how fast people actually travel when they're driving cars. I want to consider actual average road speeds, and also consider the time they spend earning the money to pay for their car and its maintenance.

Traffic Speeds

Average speed of urban traffic in Australia, by time. Source:, page 104

This paper, has the 2005 statistics for vehicle speeds in Australia. From it I got this figure, showing that the average speed of cars in urban areas during the day time is about 42 km/h. Of course, congestion has got worse since then, and I would expect average speeds today to be lower, but I couldn't find those statistics.

Combine with time spent earning the money to pay for the car

Across Australia, once on the road, your average speed in the city is about 42 km/h (more like 37 km/h during peak periods). But what about the time you spend earning money to pay for your car? To work this out, I extended this spreadsheet (previously introduced in this article). It now also calculates the average speed of a motorist, based on the 42 km/h on-road speed and the time they spend earning money to pay for the car.

The average speed they attain depends on how much they drive -- as someone drives more, the marginal (time) cost of each extra kilometer decreases so their average speed increases. Here are some examples:
  • For a person on an above-average wage, driving 10000 km per year, they average just below 23 km/h
  • For a person on the same wage, driving 5000 km/year, they average just below 18 km/h
  • They won't reach an average of 30 km/h until they are driving 80000 km/year
  • For a person on $40000/year driving 10000 km/year, they average 18.5 km/h


  1. When you consider the time spent to pay for a car's maintenance, and the actual speed you achieve on the road, cars are not actually a quick way to get around. 
  2. The cost, to the taxpayer, of car infrastructure is huge -- I question whether it is good value for money.
This article was written by Angus Wallace and first appeared at


  1. Hi Angus. Interesting. I avoid all forms of peak hour traffic like the plague. But nothing beats the comfort of the country trains on the Bendigo line as they rocket into Melbourne at 130km/h. You can't read the ADR or fall asleep when driving, but you can on the train! It is frightening how much cars cost. I service mine regularly and fix it when it goes wrong, but mostly I'm going to try and run it into the ground (hopefully). Do you have a car? Cheers. Chris

  2. Hi Chris, Yeah I own one, which doesn't please me, however we own only one which (compared with households that own multiple cars) saves us a lot of money. I want to find a neighbour who is keen to car-share, because most of the time our's sits in the driveway (I worked out yesterday that we've done about 20000 km in the last 5 years -- including driving from Brisbane to Adelaide via the coast -- we don't use it much). That way we can share the expenses...

    Cheers, Angus


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