An average car, sat idling, can produce exhaust emissions to fill 150 balloons. That's a lot of balloons to imagine puffing away out of the cars idling outside a school for a pickup, say. Other tests have found (pdf) that for any time over 10s fuel use and emissions are always greater when idling than turning off the engine and restarting. Spread the word.

Of course, if you have an electric car this won't apply.

I did draw 150 balloons, but a few of them didn't fit on the page.

Idling

Back in 1865, a chap called William Stanley Jevons noted that while there had been a number of improvements in coal efficiency in steam engines and the like, instead of reducing consumption the effect was to increase consumption instead — Jevon's paradox.

While it’s not a surefire outcome, there are plenty of parallels like more efficient batteries leading to more overall battery use, washing machines leading to doing more washes rather than less time spent washing, or the ability to recycle some plastics leading to more overall plastic consumption.

This is sometimes known as the rebound effect.

Also see the fifth fuel: energy efficiency, and save some landfill.

Jevon’s Paradox

This is the idea that people across history budget on average about an hour a day for traveling. Originally observed by Yacov Zahavi, it came from the observation that even as our means of transport sped up, instead of traveling less each day we would just travel further. As in the sketch, this leads to a conclusion that the size of our cities increases partly according to how efficiently we can travel in and out—they generally increase to a size that maintains about an hour round-trip journey.

Cesare Marchetti observed that Greek villages and ancient walking cities, for example, as marked by ancient city walls, tend to share a radius of about 2.5km. Walking at a typical 5km/hr that makes an hour round trip journey. He also pointed out that: “Even people in prison for a life sentence, having nothing to do and nowhere to go, walk around for one hour a day, in the open.”

Unfortunately, if you live in London, the average round-trip seems to be an exception of 1h30.

This is also known as the constant travel time budget hypothesis.

Also see isochrones. It might be interesting to look at these according to transport method…

Image adapted from: Marchetti, C., 1994: Anthropological Invariants in Travel Behavior, Technological Forecasting and Social Change , 47 :75–88, Internal Publication, International Institute for Applied Systems Analysis.

Marchetti’s constant

This is surely at least part of the reason that “software is eating the world.”

But I’m sure coffee will stick around for a bit too.

Rival and non-rival goods

I think it would be interesting if we could see the real shape of your favourite crossing marked on the road. It’d probably help more people cross and traffic get stopped less. And, hopefully, no casualties.

Our senses are built to take in information at human pace

The real shape of a crossing

An amazingly simple, and ridiculously useful and successful mechanism that converts linear motion to rotational motion. It’s basically what allows us to take a force produced by, say, steam, or an explosion, and make a wheel turn. Stick a few of these together and time the rotation of each correctly, carefully controlling the explosions and the exhaust and you have an internal combustion engine that powers our cars. There’s a lot amazing to me about it, but I am still impressed with how effectively it takes something moving back and forth, and makes something spin round, and vice versa.

Sketchplanations tagged with cars