As people around me on the southern motorway in Auckland were whizzing along at 110kph to 120kph (and beyond) yesterday I began to wonder what difference those speeds made on CO2 (and other) emissions.

I was thinking this because in talking to people I do find many are concerned by about climate change and many of those bemoan the government's relatively passive approach and official "adaptation" (ie: do nothing, really) policy. 

Assuming one takes the issue seriously (the evidence is now very clear that we should) the next thought is something like: "Well....what can I do now right now that will make any difference?" 

One of the answers is simply: slow down. 

When driving at 115kph in a 1.4L-2.0L petrol-powered car you're producing over 50% *more* CO2 than if you just drive at 100kph. Those are defacto "illegal" and unnecessary emissions as those speeds are illegal anyway. At 130kph over the limit you're off the chart and more than double the emissions at 100kph.

So....here is a simple, practical thing each of us who drive petrol cars (I still own one, too) can do, right now - today - to reduce our CO2 emissions.

Even you don't care about emissions, you can save 12% to 18% of your motorway (at least) fuel costs by driving at 100kph instead of 120kph. 

(source) Note that the EU cars often have higher emissions standards than apply in NZ