Slowing cars causes increased pollution

I FIND it unbelievable that a recent correspondent could say that reducing speed limit from 30mph to 20mph is good for the environment.

Absolute rubbish. Modern cards have been designed to run in top gear, somewhat uneasily, at 30mph. Reducing that to 20mph means fourth or third gear, hence a big increase in fuel used to cover the same distance.

Now try to convince me that all the additional exhaust fumes per mile is good for the environment. Logic, not waffle, is what we need.

Far more sensible would be to enforce the 30mph limits. That would entail a greater police presence on the streets (now there’s a laugh).

Could it be that all the 20mph talk is just a smokescreen to hid the fact that we do not have the manpower to enforce the 30mph limit? Not to be taken as a dig at the police, but the idiots in government.

Mr G Ledger, Horseman Close, Copmanthorpe , York.

Comments(9)

ColdAsChristmas says...
3:03pm Mon 3 Sep 12

There is no fixed penalty for 30mph for a start. This is just hysteria and bandwagon intended to bring further gridlock to overcrowded York. Someone needs their head seeing to, sooner rather than later! Who is paying for all the new 20mph signs? If road safety is the issue then how about getting rid of the humps, causing damage to vehicles and resurfacing the roads without leaving a ton of loose chippings for skidding on.

Buzz Light-year says...
7:22pm Mon 3 Sep 12

Could it be that all the 20mph talk is just a smokescreen to hid the fact that we do not have the manpower to enforce the 30mph limit?

Um, no.
It's the agenda of a small group of determined people who want to impose their will on everyone else, with reckless disregard to anything other than their opinion.

smith63 says...
8:50pm Mon 3 Sep 12

"I FIND it unbelievable that" the author asks for "Logic, not waffle", and then backs this up with opinion. Logic would be supplying information (e.g. http://mpgforspeed.c
om/) such as the best efficiency appears to be at 55mph. Would the author then justify this speed for urban travel? However, since there is no substantial change in efficiency when cruising between about 20 and 65mph, it may be more sensible to add the fact that it is the time taken accelerating and braking that reduces fuel efficiency on urban roads. Since less time must be taken accelerating to 20, rather than 30mph, you have to show some data to back up your claim.

emen says...
6:02pm Tue 4 Sep 12

smith63 wrote:
"I FIND it unbelievable that" the author asks for "Logic, not waffle", and then backs this up with opinion. Logic would be supplying information (e.g. http://mpgforspeed.c

om/) such as the best efficiency appears to be at 55mph. Would the author then justify this speed for urban travel? However, since there is no substantial change in efficiency when cruising between about 20 and 65mph, it may be more sensible to add the fact that it is the time taken accelerating and braking that reduces fuel efficiency on urban roads. Since less time must be taken accelerating to 20, rather than 30mph, you have to show some data to back up your claim.
An excellent post. Most cars are indeed most efficient when maintaining a constant speed of between 40 and 50 mph. However it is impossible to maintain a constant speed when in an urban environment but steps should be taken to keep traffic moving wherever possible.

From an environmental point of view the council should try to ensure as smooth a traffic flow as possible by intelligent traffic light phasing and well planned junctions. Maybe it's even time to consider making the entire inner ring road a one way loop.

Personally I would be much prefer to drive through town at a constant 20 mph rather than a stop/start 30 mph. The most environmentally unfriendly car is one that is stuck in a queue waiting for the lights to change.

pedalling paul says...
7:35pm Tue 4 Sep 12

Seems yet again that very few commentators are able to acknowledge that their car is everyone else's traffic. Forget the TV car ads. You don't buy an open road or a gorgeous blond in the passenger seat. If you take your vehicle on road at peak times, expect a slow journey.

emen says...
8:53pm Tue 4 Sep 12

pedalling paul wrote:
Seems yet again that very few commentators are able to acknowledge that their car is everyone else's traffic. Forget the TV car ads. You don't buy an open road or a gorgeous blond in the passenger seat. If you take your vehicle on road at peak times, expect a slow journey.
Very few people can actually afford to buy a new car and even fewer will buy a new car based on the dreams of a few marketing types. The vast majority of cars are bought as a means of transport. Like it or not cars are a reality of modern life. There are just short of 27 million of them in this country and no matter how expensive or inconvenient motoring becomes people will still use them. Simply look at traffic levels in the congestion zone in London for proof.

So, given that people are still going to use them and given that we have an economy that depends on their use, we should find ways of minimising the impact of them on the environment. Through EU and UK legislation, average fuel consumption has already increased tremendously over recent years but only for cars that are moving. Cars that are stood still in traffic queues are the problem.

Whilst the anti-car brigade might take pleasure in creating greater inconvenience to car users in the vain hope that eventually they'll give up their car and hop on a bus, the reality is that this inconvenience invariably creates unnecessary damage to the very air we breath.

greenmonkey says...
9:10pm Tue 4 Sep 12

So who are the 'anti-car brigade'? What is emen's solution to the ever increasing demand on finite road space in a historic city? The more people on buses walking and cycling the fewer in the queue of metal boxes in your way, and the more of us getting where we want to in the minimum amount of time

emen says...
9:28am Wed 5 Sep 12

greenmonkey wrote:
So who are the 'anti-car brigade'? What is emen's solution to the ever increasing demand on finite road space in a historic city? The more people on buses walking and cycling the fewer in the queue of metal boxes in your way, and the more of us getting where we want to in the minimum amount of time
Personally I'd consider prohibiting cars from most of the city centre during the day and make the majority of the inner ring road a one-way, twin lane loop with far fewer traffic light controlled junctions.

I'd look at moving the centre car parks from the centre to the inner ring road and provide a regular and reliable shuttle service into the centre.That would leave the centre as a cut through for buses and taxis and other registered users.

I'd consider creating major distribution centres on the outskirts of town and then use a fleet of electric vans to shuttle goods into the centre.

I'd like to see all buses comply with Euro 4 legislation and insist that taxis have stop-start technology.

All very radical but without radical solutions you'll not solve the problem that people will stay in their cars no matter how inconvenient you try to make it. You are right in that there is a finite amount of road space but much of it is unused whilst cars queue at the bottlenecks.

However if you prefer breathing in toxins and pollutants all day long then do nothing.

old_geezer says...
9:33pm Wed 5 Sep 12

I simply don't know whether 20mph would increase or decrease pollution. What I am sure of is that the answer has to relate to real-life performance of a city-wide population of vehicles. Apparently the optimum speed for an typically-connected urban street network is 17mph. In other words, crisscrossing journeys can't average more than 17mph. So reducing from 30 shouldn't increase average journey times, hence probably won't increase pollution. Might even decrease it if journeys are smoother.

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