Slowing Down Increases CO2 Emissions...

[st13phil]

...so says new research conducted by the AA linky

Quote:

A shock new study shows that driving at 20mph instead of 30mph actually pumps out more CO2. Research carried out by the AA has revealed that slowing traffic down can boost carbon dioxide levels by as much as 10 per cent.

And the motoring organisation is warning local authorities that well intentioned safety schemes could backfire in environmental terms. The hike in CO2 is due to the fact that cars aren’t at their most efficient when running very slowly.

The AA‘s investigation claims a petrol model on a 20mph street could emit nearly one tonne of extra CO2 per mile. “Transport planners have minimal official guidance on the environmental impact of 20mph speed limits,” explained AA president Edmund King. “It would be a bitter irony if local authorities are found guilty of pumping up emissions through the indiscriminate use of these restrictions.”

No sh*t, sherlock...

 

[Rose Chap]

I expect this news will be quietly buried by the Speed Kills/environmentalists lobby.

 

[Dieselman]

Why would the environmentalist lobby want to ignore this information? Surely it supports their case.

 

[BTB 500]

The AA‘s investigation claims a petrol model on a 20mph street could emit nearly one tonne of extra CO2 per mile.

That's total garbage. No car emits a tonne of anything per mile. Per YEAR maybe.

 

[st13phil]

That's total garbage. No car emits a tonne of anything per mile. Per YEAR maybe.

I wondered who'd be the first to spot that. Based on say 220g/km emissions (low speed running will be worse than the published emissions figure), a 10% worsening in emissions at 20mph rather than 30mph, and approximately 3,000 miles pa travelled in the low speed zone I'd say the increase would be nearer 100kg pa.

 

[Shude]

That's total garbage. No car emits a tonne of anything per mile. Per YEAR maybe.

Yeah I was thinking that! Even if a sausage of solid carbon was extruded from the tailpipe it probably wouldn't weigh that much after a mile

 

[BTB 500]

Yeah I was thinking that! Even if a sausage of solid carbon was extruded from the tailpipe it probably wouldn't weigh that much after a mile

And after two miles emitting a tonne per mile the car would have a negative weight and would shoot skywards

 

[Dieselman]

That's total garbage. No car emits a tonne of anything per mile. Per YEAR maybe.

That's probably what they said, it's just been reported incorrectly.

 

[Alfie]

I expect this news will be quietly buried by the Speed Kills/environmentalists lobby.

I think the environMENTALists would disregard it on two fronts.

1). It claims we should speed up.
2). The figures are wrong.

If they support it and its then shown to be rubbish (as it is) then they will be even more discredited than they are now

 

[grober]

Dare I introduce the novel concept of the gear box. You know the little box of rapidly rotating cog thingies that connects your engine to the wheels. Increased CO2 at low speed is almost certainly because the car will be in a lower gear= higher engine rpms= more C02 emitted. At the other end of the scale at high speed DRAG becomes major factor. Of the top of my head at 100mph an increase of 1 mph requires another 10bhp = lots more CO2 . Depending on how slippery your car is of course. Lots of design factors to be taken into consideration including engine management systems specifically set up for favourable results in fuel consumption tests and CO2 emissions make such findings fairly meaningless.

 

[Bobby Dazzler]

At the other end of the scale at high speed DRAG becomes major factor. Of the top of my head at 100mph an increase of 1 mph requires another 10bhp = lots more CO2 . Depending on how slippery your car is of course.

By way of example, theoretical values for 2004 W203 C200K:

100 mph requires 59.7 bhp at the wheels
101 mph requires 61.0 bhp at the wheels

138 mph requires 129.2 bhp at the wheels
139 mph requires 131.6 bhp at the wheels

 

[Brian WH]

By way of example, theoretical values for 2004 W203 C200K:

100 mph requires 59.7 bhp at the wheels
101 mph requires 61.0 bhp at the wheels

138 mph requires 129.2 bhp at the wheels
139 mph requires 131.6 bhp at the wheels

I would stick at 100mph mate, no good being enviromentally unfriendly.

 

[BTB 500]

I need to do over 75 in the SL cos it drops 15mm at that speed, improving the aerodynamics. M'lud

 

[wallingd]

China. Discuss.

 

[grober]

China. Discuss.

Lots of little yellow guys using up all our air.

 

[Dryce]

I expect this news will be quietly buried by the Speed Kills/environmentalists lobby.

It's prob'ly worse for autos.

I reckon on getting worse economy at 30 than I do at 50 on normal roads (which include uppy and downny bits).

Engine running at low revs. Auto box not locked up. Uppy bits mean a gear change or engine trying to generate more power at low revs which I don't think is its optimum.

Car's aren't really designed to do 20mph. If they were then the figures measured would tell a different story.

 

[Silestanix]

Mine's the same as Dryce; The e34's alot better at a higher speed than lower; it's more economical at 50-60mph than it is at 30-40mph, because its higher up the rev range still in 3rd gear; whereas at 50, it's lower in the rev range, in 4th gear. The torque just pulls the car from lower revs.

 

[Diapason]

Be careful of what you wish for.....

...so says new research conducted by the AA linky

Quote:

A shock new study shows that driving at 20mph instead of 30mph actually pumps out more CO2. Research carried out by the AA has revealed that slowing traffic down can boost carbon dioxide levels by as much as 10 per cent.

And the motoring organisation is warning local authorities that well intentioned safety schemes could backfire in environmental terms. The hike in CO2 is due to the fact that cars aren’t at their most efficient when running very slowly.

Be careful of what you wish for.....

Unfortunately, neither are cars at their most efficient (in either fuel or CO2 terms) at 60, 70, 80, 90mph.... The logical progression of this argument is that 'for environmental reasons' we should drive everywhere at the most efficient speed for our vehicles. That would mean a speed of around 50-55mph. Didn't the government impose such a limit on motorways at the time of the fuel crisis in 1974? Perhaps someone could remind us of the exact year and the limits imposed. I don't expect that anyone on this Forum would welcome a return to that situation, and I therefore humbly suggest that, by reciprocal argument, we would be wise not to use such a justification for objection to 20mph limits - which are normally imposed for pedestrian safety reasons.

Simon

 

[Satch]

Yes, we have had this debate at a local level when Surrey County Council in one of their frequent fits of Road Safety madness put many vast speed tables on a 50 mph bypass road on the approach to and departure from a new pedstrian crossing. These were every 100m and there were four of the damn things either side of the crossing

And they all got ripped out after 3 weeks because, exactly as predicted by local residents, it forced traffic back on to the very residential roads the bypass was designed to relieve, created huge peak hour jams, wrecked suspension and public service vehicles were grounding.

But what annoyed me when all this was first mooted was the blithe and idiotic statement that these new speed tables would automatically reduce CO2 and pollution because average speed would be reduced.