I am writing to you to invite you to undertake some research on the impact speed limits have on  fuel consumption, and CO2 emissions

There has been some debate in the press this year about 20 mph limits  and a statement that 20 mph roads pump up CO2 emissions by 10%

It seems that this statement was based on a comparison between fuel consumption of petrol powered cars driven at a continuous speed of 20 mph and at 30 mph.

The flaw in this comparison will be immediately apparent to anyone who has attempted to drive in an urban area at a continuous speed of 30mph. You crash at the first junction you come to.  Urban driving is full of stops and starts.  So what is the actual impact on fuel consumption and carbon dioxide emissions of urban 20 mph speed limits?

I would be truly grateful if you have a car with a trip computer you would do your own experiment and share the results:

1. chose an urban route representative of a typical journey – say 2 -4 miles in length.

2. undertake 2 separate journeys – one observing a self-imposed 20 mph limit – and one 30 mph.  (or as many journeys as you like!)

- please make sure the engine is at the same temperature when starting both journeys: either fully warmed or totally cold - preferably the latter.

3. Record the

                        type of car  

                        automatic or manual

                        petrol or diesel

brief description of the route.

                        And for each journey:

average speed,

average fuel consumption

distance travelled,

whether the engine was hot or cold,

if you can count the number of times you apply the brakes – so much the better

imperial units preferred

4. And let me know direct – Robert.huxford@...

I will send out a compiled report to the Streets forum as soon as we get enough results.

If you want to contact me direct before you start your trials please feel free!

Many thanks

Robert

Robert Huxford

0791 34 34 366

01732 851 872