From: GT on

"mileburner" <mileburner(a)btinternet.com> wrote in message
news:i2bp07$ad9$1(a)news.eternal-september.org...
>
> <boltar2003(a)boltar.world> wrote in message
> news:i2bkgp$i15$1(a)speranza.aioe.org...
>
>> No it isn't. Cars have an optimum speed at which they use the least fuel
>> for a given distance and its usually somewhere around the 50-60mph mark.
>> Above and below that fuel economy starts to drop off a cliff. Thats what
>> makes
>> all these "green" initiatives by local councils slowing traffic down to
>> 20mph
>> such a joke. It just generates more CO2 and probably causes more bad
>> driving
>> when drivers get back onto a main road and floor it to make up lost time.
>
> OTOH the 20 mph limits encourage drivers to drive at a speed where they
> are not continuously (and often aggressively) speeding up and slowing
> down.
>
> In urban areas, how long can 30mph be maintained before reaching a set of
> lights, pedestrian crossing or other give way, stop etc?

For exactly the same distance as when driving at 20!

> Lost time from travelling at 30 is often gained by less time waiting in
> traffic queues, so the overall time of the journey can make little
> difference and fuel economy can be better.

That doesn't make sense - lost time from travelling at 30 being gained by
waiting less? This is an argument in favour of travelling at 30 and I think
you were trying to promote 20?

Fuel economy at 20 is worse than at 30, so a journey at 20mph would use more
fuel than the same journey at 30mph. An identical journey at 30mph would
take less time on average than the same journey at 20 as it would pass
through the same streets, traffic lights etc, so would typically stop in the
same places. The journey has to take longer because you are going slower -
thats pretty simply!

In fact, some cities set timings on lights so that a stream of traffic
leaves one set of lights as it turns green and at 30mph will arrive at the
next set of lights as they change to green too. So travelling at 30 would
result in less stops and delays than travelling slower than the limit.


From: boltar2003 on
On Fri, 23 Jul 2010 10:43:17 +0100
"mileburner" <mileburner(a)btinternet.com> wrote:
>> What a load of drivel.
>>
>> Stop bike.
>>
>> Get off and stand next to wall/bush.
>>
>> Let cars past.
>>
>> See , not hard is it?
>>
>> B2003
>
>The only thing is that if you all-of-a-sudden stop, and get off you bike,

Why would you do a sudden stop? Stick your arm out so drivers know you're
stopping and coast to a halt.

>It is far better to wait until there is an appropriate shoulder, lay-bay,
>side exit etc. where you *can* stop and get out of the way and let them
>pass. Even better, just wait for the road to widen (or otherwise be safe to
>pass) and pull over and wave them past. Then there is no need to hold up the
>traffic or put anyone at risk.

In an ideal world yes. In a narrow road that you might be puffing your
way up for the next 10 minutes its only good manners to let other traffic
pass.

>Boltar's cycling advice is not really very good. I can't imagine why...

My cycling advice would be - don't bother, buy a car. Unless you live
somewhere like holland then any trip will involve hills and hills involve
sweating. No one wants to sit next to someone who stinks of sweat in an
office.

B2003

From: Albert T Cone on
boltar2003(a)boltar.world wrote:
> On Thu, 22 Jul 2010 22:00:01 +0100
> "DavidR" <curedham(a)4bidden.org.uk> wrote:
>> "Jethro" <krazykara0(a)googlemail.com> wrote in message
>> news:6842a0c5-6d67-4d78-a6b5-7ce0b485caa7(a)q35g2000yqn.googlegroups.com...
>>> Having just watched a number cars grinding up a hill near me (I was
>>> walking) because a cyclist was at the head of the queue, and it was
>>> too twisty and narrow to safely overtake, I started wondering about
>>> the OVERALL effect cyclists have on carbon emissions.
>>>
>>> Does all the extra carbon produced by cars having to crawl behind
>>> cyclists cancel out, or exceed the carbon saved by the cyclist ?
>> The loss of mechanical efficiency from using a lower gear is probably
>> cancelled out by the reduction in aerodynamic loss. The biggest effect is
>
> No it isn't. Cars have an optimum speed at which they use the least fuel
> for a given distance and its usually somewhere around the 50-60mph mark.
On the flat, without a headwind. And the peak can be anywhere from
25-60mph. On a hill, the optimum speed can be very different.

> Above and below that fuel economy starts to drop off a cliff.
Generally not really. In my diesel panzer, sorry, passat, I get about
50mpg at 50 in 5th, 46mpg at 40 in 4th and 47mpg at 30 in 4th.

> Thats what makes
> all these "green" initiatives by local councils slowing traffic down to 20mph
> such a joke. It just generates more CO2 and probably causes more bad driving
> when drivers get back onto a main road and floor it to make up lost time.
They certainly don't save the planet. They *sometimes* encourage
traffic onto roads better designed to carry it and make side roads a bit
more pleasant, but I'm pretty sure that that is by accident rather than
design.
From: boltar2003 on
On Fri, 23 Jul 2010 12:15:56 +0100
Albert T Cone <a.k.kirby(a)durham.ac.uk> wrote:
>> No it isn't. Cars have an optimum speed at which they use the least fuel
>> for a given distance and its usually somewhere around the 50-60mph mark.
>On the flat, without a headwind. And the peak can be anywhere from
>25-60mph. On a hill, the optimum speed can be very different.

Possible , I'm not an expert in this. But I was under the impression that
IC engines have an optiumum rev range and if you keep within that range
then no matter what the load you'll achive the best possible fuel economy.

B2003

From: Brimstone on

<boltar2003(a)boltar.world> wrote in message
news:i2brj4$ubu$1(a)speranza.aioe.org...
> On Fri, 23 Jul 2010 10:43:17 +0100
> "mileburner" <mileburner(a)btinternet.com> wrote:
>>> What a load of drivel.
>>>
>>> Stop bike.
>>>
>>> Get off and stand next to wall/bush.
>>>
>>> Let cars past.
>>>
>>> See , not hard is it?
>>>
>>> B2003
>>
>>The only thing is that if you all-of-a-sudden stop, and get off you bike,
>
> Why would you do a sudden stop? Stick your arm out so drivers know you're
> stopping and coast to a halt.

Most car drivers don't know hand signals.

>>It is far better to wait until there is an appropriate shoulder, lay-bay,
>>side exit etc. where you *can* stop and get out of the way and let them
>>pass. Even better, just wait for the road to widen (or otherwise be safe
>>to
>>pass) and pull over and wave them past. Then there is no need to hold up
>>the
>>traffic or put anyone at risk.
>
> In an ideal world yes. In a narrow road that you might be puffing your
> way up for the next 10 minutes its only good manners to let other traffic
> pass.

Why should people sitting in nice comfy overpowered cars get precedence over
people using muscle power?