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Cars & traffic

Oct 18, 2012

Is "Effective Speed" a useful concept?

"Effective Speed" relates travel time to hours worked and, at first glance, seems like an interesting perspective. Closer inspection suggests it's neither especially insightful nor particularly useful.

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Empty America - what San Francisco would look like without people

I might be late to the party on this one, but until I read this article on The Conversation this week, I hadn’t heard about the concept of “Effective Speed” before.

As explained by Dr Paul Tranter, a geographer at UNSW, Effective Speed takes into account all the time costs of a mode of transport, not just the in-vehicle time.

He says the time spent earning the money to pay for a car is usually much greater than the time actually spent driving. He cites this anecdote:

Imagine living in a village, where your job each day is to collect a bucket of water from the river. This takes an hour each day. To “save time” you build a machine to fetch the water. However, to make the machine work, you need to spend two hours each day winding up a spring.

In modern cities, he says, the equivalent of “winding up the spring” is the time spent at work earning the money to pay for transport. Driving to work might be considerably faster than using public transport or cycling,

However, motorists might be spending one or two hours per day (or more) earning the money to cover the cost of their cars, while cyclists spend only a few minutes per day earning the money to pay for their bicycles.

The term Effective Speed sounds very much like “Effective Density”, another relatively new and modish term. Effective Density combines job density and commute time in a single statistic.

I’m wary about the justification for combining a mere two ideas – both of them quite simple and straightforward – into a new and unfamiliar concept. Effective Density seems like an idea searching for a rationale (perhaps it’s about marketing more than anything else).

But at least Effective Density is conceptually logical. I’m not so sure the same can be said of Effective Speed. At first glance it’s appealing but on reflection it appears to be more illusion than logic.

It’s sensible to think about the full cost of transport (e.g. owning and operating a car) in terms of hours worked or money earned. But it’s not clear that comparing hours worked against hours spent driving adds anything or is even a useful way of thinking about transport.

To begin with, travel time leaves out a long list of other reasons people have for owning and operating a car. It’s not just speed – cars are attractive because they’re available on demand and go direct to the destination.

They also enable multiple passengers to be carried, as well as various objects like shopping or spare underwear. They offer privacy and personal security, protection from the weather and a high degree of comfort. Many drivers are also prepared to spend more (i.e. work longer hours) on a car  in order to communicate status.

Any metric that doesn’t factor in these attributes has limited explanatory power. My reservations go further though – what I don’t get is the premise that there’s a direct and special relationship between hours worked and hours spent driving.

Consider this example: I might work for six weeks to pay for a one week luxury holiday in the best hotel in Paris. The cost matters because I have to be able to afford it and I want value for money.

But how is evaluating the choice in terms of the length of the two time periods particularly important or illuminating? Is the trip not worth it because it’s much shorter than the time I have to work to pay for it? What matters is that I think the overall bundle of benefits exceeds the costs.

I suspect Effective Speed only seems appealing because both sides of the equation involve time. But if it’s a useful idea it ought to work for all the activities we labour to support.

What does it mean if I work one week a month to pay the mortgage? Or to pay school fees?  Or buy food? These are “effective”…….what exactly?

The limitations of Effective Speed are illustrated by this quote from Dr Tranter:

The higher trip speeds of cars do not save time; instead they encourage longer travel distances as the city spreads out and local shops, schools and services close.

Using travel time as the sole metric means the range of private benefits drivers get from their cars is ignored. The longer travel distances made possible by higher speeds mean drivers have a wider choice of destinations.

That might mean, for example, that they drive to better jobs, better dentists, better schools, or visit distant parents more frequently. Travel time is just a means to an end that, from the driver’s perspective, confers a private benefit and so is worth paying/working for (of course cars have social costs too, but that’s not what this discussion is about).

I’m not saying Effective Speed is “wrong”. I’m saying it doesn’t seem to be either particularly insightful or particularly useful.

Alan Davies — Editor of The Urbanist

Alan Davies

Editor of The Urbanist

The Urbanist is edited by Dr Alan Davies, a principal of Melbourne-based economic and planning consultancy, Pollard Davies Consulting.

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18 thoughts on “Is “Effective Speed” a useful concept?

  1. Last name First name

    Parker Alan. OAM
    Speed is controlled by speed limits that are enforced. This is why
    The European Parliament adopted a resolution in 2011 that “strongly recommends the `responsible authorities to introduce speed limits of 30 km/hr in all residential areas and on single lane roads in urban areas which have no separate cycle lanes “ This resolution is is part of a wide range of measures to halve Europe’s 31,000 annual road fatalities by 2020. (Kock Report 2011)

    The latest information from Europe is that a 30 kph limit on local roads and main roads in busy urban areas heavily used by walkers are much safer for al non-motorised users, motorised wheelchairs and electric bicycles. Compare this with the overall road safety record of the Netherlands and Australia shown on table 2.
    It is very clear that on the basis of kilometres ridden by bicycle in the Netherlands is still safer even though no one is compelled by law to wear a bicycle helmet. From the pedestrian fatality rates per 100,000 population for Australia and the Netherlands it is clear that since 1965 the Netherlands has been much safer for both pedestrians and cyclists. The Dutch government believes that the 30 kph limit is of great benefit to all non-motorised users”

    It is also assumed that riding a 25 km) speed limited electric bicycle “pedelec” is as safe as a bicycle given the existence of a low speed limit. This assumption is soundly based on data from selected bicycle friendly EU countries which have the following 2010 road death rates per 100,000 population: , Sweden 3.0, Netherlands 3.7, Japan 4.3, and Germany 4.7, Denmark 4.5, Switzerland 4.5 France 6.1. Australia’s death rate is higher (6.2) and the US death rate of 10.5 is even higher.
The European bicycle friendly countries are safer for all road users.

  2. boscombe

    Completely agree, Alan. I read that article and couldn’t see the sense of it. Everyone knows about the wonderful benefits of cycling or using public transport, but most people would have to be forced to give up using cars, and for good reasons.

    I gave up years of commuting by train when the crowding became unbearable. I tried buses and found them unreliable, uncomfortable and very time consuming. Commuting by car saves me at least an hour a day, which I use for a bit of a run and swim at the beach. I stop on the way home from work to pick up shopping or dry-cleaning, or see a movie … many things. I take my lunch to work in several glass (don’t like plastic) containers, and on the way listen to CDs if I don’t like the radio. Should be listening to learning Mandarin CDs but am at present hugely enjoying tango CDs picked up recently in Buenos Aires.

    A colleague brings her harp into work on Thursdays, because she goes off to her harp lesson at lunchtime. She’s even older than I am and might have difficulty managing the harp on a bike, or on and off the bus.

    Perhaps like many other people I can’t be sure when my work day will end … I thought today it would be six, but it was nearer seven, and could have been ten – I can imagine my public transport options outside peak hour, or the joys of riding a bike home 15 kms in the dark.

    Another article on The Conversation recently suggested people move closer to work and walk or cycle. Apart from the unaffordability, that assumes that people only go to work. I go to the beach every morning, and in summer, go after work as well …. that’s why I live near the beach!

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