We are drifting (at about 20 mph) off-topic.
Greater emissions at 20 mph? Please see:
An evaluation of the
estimated impacts on vehicle
emissions of a 20mph speed
restriction in central London
‘Section 5 detailed the development of London-speci
fic 20mph and 30mph drive cycles for use with
instantaneous emissions databases. The effects of
a 20mph speed restriction on were shown to be
mixed, with particular benefit seen for emissions
of particulate matter and for diesel vehicles. The
methodology was validated by consideration of
real-world tailpipe emissions test data. It was
therefore concluded that air quality is unlikely to be made worse as a result of 20mph speed limits
on streets in London. This analysis is suitable for per-vehicle emission rates, and does not consider
secondary effects such as congestion.’ (page 66).
‘I agree with Chris - the 20 limit (doubtless unintentionally) causes much more visible anti-social behaviour in drivers.’
On this argument no speed restrictions should result in considerate and careful driving by all drivers and no anti-social behaviour.
Doubtless there are times that pedestrians should take more care crossing a road but don’t forget that, for instance, elderly people’s sight may be poor and they may well unable to move quickly. I hope the new level of fines will persuade those impatient and selfish motorists to drive with greater care and to respect speed limits and that means at 20 mph in most of Lewisham.
Think Rachael is right here.
Any objections to me splitting off the posts which are debating the limits in general? I’d propose making a new topic, “The 20mph Debate - 2017 Edition,” which linked to the old debate, and to this one.
- Get splitting
- Leave this topic alone!
- Don’t mind
- Other (please comment)
0 voters
Personally I think the two topics are so interlinked youll never have one without the other. Leave it.
2 Likes
That’s a straw man, isn’t it? My own view (based on experience) is that the danger is increased for other drivers. Saying that, it’s probably better for pedestrians.
Happy to accept your data about little difference between 20 and 30 on the basis that the source looks good. Good point.
No, someone just said it.
Matching one biased source with another for balance.
http://www.rospa.com/road-safety/advice/drivers/speed/20mph-zones-and-limits/
I’ve been to a briefing on London road infrastructure where TfL advised the Mayor’s plan (current and past) to convert automobile journets to other modes of transport. They estimate as much as 4/5ths of private car journeys are unnecessary and simply put London’s roads are already at full capacity. Less car journeys less missions. Higher co2 compensated for. The suggestion that beyond road safety the 20mph which the Mayor’s office supports is part if an overall strategy to significanty change the mix of transport modes. I’ll try to find my notes and share with you. It was fascinating.
2 Likes
Genuine question. Any physicists/chemists here? A litre of unleaded weighs less than a litre of water. In rough figures call it 0.75kg.
So how does 0.75kg of unleaded produce three times its own mass - 2.36kg - of CO2?
It takes 5,000-20,000 litres of water to produce 1kg of meat.
I guess the fuel statistic took into account the whole lifecycle?
??? That’s MORE water producing LESS meat - which makes sense. How does less become more?
The production and transportation of petrol produces CO2.
Ah. Yes, I see what you mean, now. That’s not how I read the data but I guess that could be the answer.
“The amount of carbon dioxide (CO2) that is produced from burning a fuel weighs more than the amount of the fuel itself, because during complete combustion, each carbon atom in the fuel combines with two oxygen atoms in the air to make CO2. The addition of two oxygen atoms to each carbon atom forms CO2, which has an atomic weight of 44—roughly 3.6667 times the atomic weight of the carbon, which is 12.”
6 Likes
Got it! Thank you! So it’s the combination of the mass of the petrol and some quantity of mass of air in which it combusts that produces ‘more’ CO2.
Thanks, @Foresthillnick!!
Phew guys what’s that in sweetie weight, gases etc 
In other words, the only changes are likely to apply to the worst offenders and only then when they land in court?
In other news: Telegraph newspaper guilty of click-bait headlines… (see OP)
1 Like
20 mph is just a joke if I put my car in 4th gear take my feet off the accelerator my car will do 27mph the roads are for everyone but in saying that we all have a duty of road safety pedestrians need to cross in the right place not just walk out in between parked cars cyclists need to obey the highway code and hopefully the roads will be a safe place for everyone
Sounds like your car is in urgent need of a mechanic or taken off the road.
2 Likes