20mph speed limit in residential areas to be made law (In Wales)

forgotmyname

Reducing pollution in your car maybe not my car which was built to cruise motorways all day.  Needle bang on 70mph probably
more like 67/68 it was over 60MPG. Signs saying slow 50mph to save the planet, not sure how im now using more fuel and had
to drop a gear. Now doing 52MPG.  How is that saving anything?

Grumpy_chap

forgotmyname said:

Reducing pollution in your car maybe not my car which was built to cruise motorways all day.  Needle bang on 70mph probably
more like 67/68 it was over 60MPG. Signs saying slow 50mph to save the planet, not sure how im now using more fuel and had
to drop a gear. Now doing 52MPG.  How is that saving anything?

No need to drop the gear down when still cruising at 50 mph.  Then you will use less energy - it is simple physics.

Stubod

Username03725 said:

I tend to drive around 50 anyway as I find it more relaxing and better for mpg, but I am also conscious of following traffic which I will help them to overtake were possible, or alternatively I will pull over and let them pass....

Hmm. I'm sure you're a lovely chap and kind, thoughtful, good to your kids and look after small animals etc, but this is what frustrates those of us who prefer to make reasonable progress. You're "conscious of following traffic [and] will help them to overtake were possible", but that means where it's not possible your desire to have a relaxing trundle along at 50 saving a tiny miniscule amount per mile in fuel costs overrides everyone who isn't just out for a relaxing pootle and would rather be on their way to where they need to be. Again - it's not the time factor, it's the feeling of being held up for no good reason other than someone deciding that his/her own personal speed limit overrides the prevailing posted limit.

Not for nothing is 'failure to make reasonable progress' a driving test fail.

..LOL...as for "failing the test"....I think not, I would not consider driving at 50 in a 60 limit "unreasonable" progress anyway, and I won't be changing my driving habits anytime soon.

I appreciate the feedback and it gave me a chuckle..

Stubod

forgotmyname said:

Reducing pollution in your car maybe not my car which was built to cruise motorways all day.  Needle bang on 70mph probably
more like 67/68 it was over 60MPG. Signs saying slow 50mph to save the planet, not sure how im now using more fuel and had
to drop a gear. Now doing 52MPG.  How is that saving anything?

...I think your car needs a bit of a tune up if it can't maintain 50mph in top gear?

I understand that the power needed to overcome wind resistance goes up exponentially, so you need a lot more power to drive at 60 than you do at 50, and therefore fuel.....which is running out....apparently...

Username03725

No probs Stubod, I'm not trying to provoke a fight, just standing up for driving at or close to speed limits when reasonable.

The problem with wanting limits reduced is that the people who are keen (like yourself SB) aren't really affected by any reduction. You (as a loose group) aren't hindered by existing speed limits, you always have a clear road ahead of you to drive along and aren't troubled by drivers whose approach to speed limits differs from yours. You amble along with a smile on your face, nice and relaxed and getting 0.2mpg more out of your petrol. So a reduction in limits has no effect on your travel arrangements, it's only a positive.

You say you move over when you can, but you have no idea how much angst and frustration is building up behind you. I've admitted that it frustrates me (I might mutter F F S when it happens) but then I'll wait until it's safe not be be behind you, so all you briefly see is me passing you and going off down the road - a few seconds elapses and you forget that my car ever existed. Whereas I've had potentially minutes stuck behind you wishing I could get on with my day. You're lucky it's me, it might occasionally be the nutter who's all over your boot flashing headlights and blaring the horn in his impatience and who passes you then cuts you up as he does before roaring off at 90. What a nutter eh. But who provoked him?

Btw doing 50 in a 60 is borderline unreasonable, hence me being nice. But it's not driving with other road users' needs at the forefront of your actions is it? It's very much a me me me, and everyone behind you has to accommodate your preferences, whereas not many people are held up by those of us going at or close to the limit, and the ones that are are borderline illegal anyway.

Your arguments for reducing speed limits don't add up. Let's hope they're safely ignored.

so you need a lot more power to drive at 60 than you do at 50

Not so. The current mpg reading in my car barely changes whether I'm doing 50 or 60. It's a miniscule difference in most modern cars.

Stubod

U

so you need a lot more power to drive at 60 than you do at 50

Not so. The current mpg reading in my car barely changes whether I'm doing 50 or 60. It's a miniscule difference in most modern cars.

..I think you will find the laws of physics will dictate otherwise? (..by all means have a google)..

NB I am not looking to pick a fight with anybody, and I am only seeking opinions as I am sure we will have no control as to what the government may or may not do.

I too was one of those motorists that used to drive "on the limit" everywhere I could only to be frustrated by lorries and other slow traffic. However I discovered that by leaving a little earlier and allowing extra time for a journey gave a whole new perspective to driving and made it a lot more stress free and pleasurable....but I guess each to their own....

Username03725

I too was one of those motorists that used to drive "on the limit" everywhere I could only to be frustrated by lorries and other slow traffic. However I discovered that by leaving a little earlier and allowing extra time for a journey gave a whole new perspective to driving

Ah that explains it - the evangelism of the smoker turned non-smoker. Right you are sir...

Stubod

..don't think I ever smoked?

..but then my memory is not what it used to be?

Username03725

It's an analogy. But you knew that.

Ditzy_Mitzy

Stubod said:

forgotmyname said:

Reducing pollution in your car maybe not my car which was built to cruise motorways all day.  Needle bang on 70mph probably
more like 67/68 it was over 60MPG. Signs saying slow 50mph to save the planet, not sure how im now using more fuel and had
to drop a gear. Now doing 52MPG.  How is that saving anything?

...I think your car needs a bit of a tune up if it can't maintain 50mph in top gear?

I understand that the power needed to overcome wind resistance goes up exponentially, so you need a lot more power to drive at 60 than you do at 50, and therefore fuel.....which is running out....apparently...

In effect yes, but it's not necessarily that simple.  Drag is an important consideration when driving in a straight line at a constant speed.  The point, however, is that different cars generate different amounts of drag.  A sports car will experience far less drag than a 4x4; so much less, in fact, that a sports car travelling at 70 mph has less drag force exerted on it than does a 4x4 travelling at 50 mph.  Assuming both have the same engine, the sports car will consume less fuel even though it's going faster.  Someone wishing to drive fast for long distances, therefore, can easily offset the drag issue by buying a more aerodynamic car.  It's a very simple problem to solve.  

Moving on to the country road issue: yes, in theory, the drag issue still holds true.  Any car will create less drag when it is being driven more slowly.  The issue is that driving slowly in top gear, as you have suggested, puts the engine out of peak efficiency.  The general state, slow speed and high gear, is the engine turning slowly in relation to the wheels.  That means it doesn't take in much air and less fuel is used.  The corollary is more effort is required on the engine's part to accelerate.  Not to maintain speed, but to gain speed or, in this sense, to regain speed if the revs drop.

Driving on a typical country road involves going round bends.  Cornering slows the car down, owing to the retarding forces applied by changing the angle of the front wheels.  In order to compensate and maintain speed, the driver opens the throttle.  Now: if the engine is 'on power', the throttle opening to compensate for the speed loss caused by steering, is lesser and shorter than if the engine is not 'on power'.  If the engine is held out of the power band by, for instance, the car being put in fifth rather than fourth, the expectation is that more throttle will be required to maintain constant speed through bends and uphill.  Logically there must be a point at which the car in high gear, because its engine is running inefficiently for what it is doing, consumes more fuel than an equivalent car in a lower gear. 

Taking all that into account, it would also be possible to compensate for the engine being out of its power band by staying in a higher gear but driving faster to increase engine revs.  More fuel would be used on the straights, but potentially less through the corners and uphill.  Swings and roundabouts.