The concept of “effective speed”

16 10 2012

On The Conversation, a science based news site started by some Australian universities, is a very interesting article on the concept of “effective speed”.

Effective speed is the time your mode of transport costs in time to use, plus the time you have to work to pay for the cost of that transport.

From the article: “For pedestrians, this time is virtually nil. For cyclists it is minimal. For car drivers, the time spent earning the money to pay for all the costs of cars is usually much greater than the time spent driving.

So the idea is that it may take 30 minutes to drive to work, so that’s an hour a day on the car use, and then the costs of the petrol are say $80 a week, and the registration, insurance, maintenance, repairs, the WOF,  the fluffy dice, interest costs on the loan, and the initial cost of the car means the cost of the car to run other than petrol is say $800 a month, and that is suddenly 2 hours a day extra working to pay for it all.  So that’s an effective speed of 3 hours a day. (The numbers are the first thing that came into my head, don’t hold me to them.)

Maybe the bus ride takes 40 minutes and costs $8 a day, which takes 20 minutes of work to pay for.

Catching the bus therefore liberates you by 2 hours a day.

Some of the comments say things like “woe there cowboy. A car is a necessity and is a fixed cost”, and it is true everyone’s effective speed calculus is going to be different because all of our situations are different, but going from a 2 car family to a 1 car family pays back bigtime with extra time, and if you can work out a way to not own a car, and it works for you than that can be truly liberating.

It’s a pity that “effective speed” isn’t used in the calculations for whether roading projects go ahead. They’re usually justified by their supposed time benefits which is a system that is frequently subject to some dodgy accounting  and completely ignores the mathematics of induced demand.

Again from the article:“Unlike drivers, increases in trip speed for cyclists could result in a substantial increase in their effective speed. This is because the main time component for cycling is the time spent on the bicycle. Increases in trip speeds for cyclists could be achieved with minimal cost.”

If governments understand the concept of effective speed they will also appreciate the futility of trying to save time by trying to increase the average trip speeds of private motor vehicles. Cities that invest most effectively in cycling infrastructure will have more time and money to devote to things other than transport, including health promotion.

Improving urban health might be as simple as valuing the time of cyclists more than the time of motorists.”

It makes building the Great Harbour Way look pretty clever, and building Transmission Gully look pretty stupid.



3 responses

18 10 2012

Thanks for bringing this to our attention, I’ve never thought of the cost factor or riding vs biking to work in this way before. Reckon I might get the calculator out tonight. Fascinating stuff. I’m reblogging this!

18 10 2012

Reblogged this on Wellington Rider.

18 10 2012

Ta Greg

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