Off yer bike - for the sake of all of us on the roads - Page 8

Theo Bekkers wrote:
>
> Tamyka Bell wrote:
>
> > The reason why traffic stop-starts is largely because people don't
> > leave enough following distance. If you leave a large enough gap, you
> > can react more gradually, and therefore you don't change speeds as
> > much. This should be bloody obvious but apparently 80% of peak hour
> > drivers don't understand it.
>
> They really have little control over the traffic density. A bunch of cars is
> travelling at the correct 2 sec gap, cars merge in from the left, next entry
> point more cars merge in from the left, and again at every entry point.
> Eventually the gaps decrease to nothing and everybody stops.
>
> Some years ago they increased the freeway speed limit in Perth from 80 to
> 100 on the reasoning that they would be able to move more cars on the
> freeway. Whilst the end to end time spent on the freeway will decrease with
> a higher speed limit, the amount of cars on the freeway remains the same.
> With a 2 sec gap you can move 30 cars per minute per lane at 100, at 80, at
> 60, and at 20 km/h. To move more vehicles you need more lanes.
>
> Theo

Or... to move the vehicles faster, you need fewer vehicles.

Tam

On Fri, 09 Dec 2005 00:24:33 GMT, dewatf@anti-hotmail.com (dewatf) wrote:

>Cyclists are also required by law to use cycle lanes when they are
>provided, to use cycle paths when directed by All Cycles signs, and to
>obey no bicycle signs.
>
>These are just the road rules.

The All Cycles signs aren't in the road rules, which makes them advisory only.
There used to be one in the ACT that I never ever saw when riding, only when driving!
Far too busy evaluating the threats as I passed it approaching the intersection.


Andre

Graeme Dods wrote:
> On Fri, 9 Dec 2005 11:10:06 +0800, Theo Bekkers wrote:
>
>> Some years ago they increased the freeway speed limit in Perth from
>> 80 to 100 on the reasoning that they would be able to move more cars
>> on the freeway. Whilst the end to end time spent on the freeway will
>> decrease with a higher speed limit, the amount of cars on the
>> freeway remains the same.
>
> That the reasoning I've always used, but then it was pointed out (here
> http://tinyurl.com/8w3s6) that as the cars are not of zero length,
> then this isn't quite true. However the gains in vehicle numbers for
> a given speed increase are very low, e.g. a tenfold increase in speed
> for a 1.4 fold increase in vehicle throughput.

Yes, I do understand that, but, for a speed increase of 25%, the effect is
almost nil. Therefore I don't factor it in the argument as most people don't
understand the maths involved. The real problem is maintaining a 2 sec gap
when stationary. :-)

Theo

Graeme Dods wrote:
> On Fri, 9 Dec 2005 11:10:06 +0800, Theo Bekkers wrote:
>
>> Some years ago they increased the freeway speed limit in Perth from
>> 80 to 100 on the reasoning that they would be able to move more cars
>> on the freeway. Whilst the end to end time spent on the freeway will
>> decrease with a higher speed limit, the amount of cars on the
>> freeway remains the same.
>
> That the reasoning I've always used, but then it was pointed out (here
> http://tinyurl.com/8w3s6) that as the cars are not of zero length,
> then this isn't quite true. However the gains in vehicle numbers for
> a given speed increase are very low, e.g. a tenfold increase in speed
> for a 1.4 fold increase in vehicle throughput.

Yes, I do understand that, but, for a speed increase of 25%, the effect is
almost nil. Therefore I don't factor it in the argument as most people don't
understand the maths involved. The real problem is maintaining a 2 sec gap
when stationary. :-)

Theo

Tamyka Bell wrote:

> Or... to move the vehicles faster, you need fewer vehicles.

Yup, you just can't put 60 cars a minute into a lane.

Theo

On 2005-12-09, Theo Bekkers <tbekkers@bekkers.com.au> wrote:
> Tamyka Bell wrote:
>
>> Or... to move the vehicles faster, you need fewer vehicles.
>
> Yup, you just can't put 60 cars a minute into a lane.

As a trainer once commented when we told him the requirements for the
billing system for a certain tollway: "That doesn't sound too hard ...
after all, think about it: voom, voom, voom [spaced at one second
intervals] is a *lot* of cars. Ok, you've got several lanes at each
gantry, and several gantries, but really: at most, you've got about 20
cars a second to deal with, and that's very little for a computer."

(Or words to that effect, anyway.)

--
My Usenet From: address now expires after two weeks. If you email me, and
the mail bounces, try changing the bit before the "@" to "usenet".

On Fri, 09 Dec 2005 12:38:14 +1000, Tamyka Bell <t.bell@uq.edu.au>
wrote:

>My point was to look ahead. Don't look at the car in front. Look as far
>ahead as you can. Change lanes early while you are still moving at
>70km/h. That's not difficult. I manage that all the time. I even managed
>that when driving in Sydney. My driving instructor taught me to look
>ahead. It should be part of basic driver education.

So two lanes of traffic change into one lane, with no traffic
disruption?
Magic!

Or is it just you change lanes and everybody else gets stuck behind
the cyclist.

>Also, while you are required to give way when changing lanes, if there
>is insufficient space to change lanes between two vehicles, then those
>two vehicles are too close.

Rubbish. The safe distance between cars is equal to the emergency
stopping distance. To change lanes when you have to give way there has
to be enough room for you to move across and then accelate without
obstructing the other car. Many more times that safe stopping
distance. Unless you just pull out illegally and force them to break
hard (which a lot of drivers do).

There is no way you can change lanes into a continous stream of
traffic driving much faster than you unless there is large gap in the
traffic, much larger than safe stopping distance.

Even if you are moving at the same speed you can then change into the
safe stopping distance, but that then forces the car behind to slow
down to re-establish safe stopping distance, which flows back up the
road, and on a road that is at full capacity causes traffic to grind
to a halt. Obviously you have never driven on the F3 in peak hour
where that happens all the time.

dewatf.

>>>>> "dewatf" == dewatf <dewatf@anti-hotmail.com> writes:

dewatf> On Mon, 05 Dec 2005 07:21:49 GMT, Euan
dewatf> <euan_b_uk@yahoo.co.uk> wrote:
>> It's a speed LIMIT, not a speed maximum. No one vehicle has a
>> right to get past the vehicle in front of him, although I've yet
>> to come across a car, truck or bus that can't get past me in less
>> than 60 seconds.

dewatf> But slow vechiles don't have a right to obstruct other
dewatf> vehicles either. Vehicles travelling slower than the speed
dewatf> limit are expected to show consideration for faster
dewatf> traffic. Nor are slower vechile permitted to merge forcing
dewatf> faster traffic to brake or take evasive action.

Oh stop talking twaddle!

A cyclist riding as a part of normal traffic, taking a lane because that
is the safest and advised thing to do is not obstructing traffic; they
ARE traffic.

Now show me the cite that says slow traffic can't merge right when the
left lane is obstructed by road works or such like.

dewatf> If you are driving at 30km/h along a 60km/h road in good
dewatf> conditions without good reason the police can fine you or
dewatf> even charge you if they consider it dangerous.

Oh there's that driving thing again. Cyclists don't drive, they ride.
The fact that the engine of a bicycle is the body pushing it is a pretty
good reason.

dewatf> Cyclists are also required by law to use cycle lanes when
dewatf> they are provided, to use cycle paths when directed by All
dewatf> Cycles signs, and to obey no bicycle signs.

Yeah, cause we've really been talking about cycle lanes haven't we?
Point of order, that only applies to on road bike lanes, not off road
lanes.
--
Cheers | ~~ __@
Euan | ~~ _-\<,
Melbourne, Australia | ~ (*)/ (*)

From Saturdays (10/12) SMH Editorial

*chuckle*

Two wheels good

READERS who have feared this week that a bout of petrol sniffing has broken out in these offices can rest easy: the Herald is not opposed to bicycles. From behind the windscreen, cycling may look laborious and be annoying, but we realise the cyclist's life has pleasures that the car folk never know. Michael Duffy argued that cyclists should be banned from the roads. Cyclists responded that, on the contrary, the world would be a better place if cycling were compulsory. We believe the truth lies somewhere in the middle, preferably in a designated bike lane where it has less chance of being run over by a semi-trailer.

dewatf wrote:
> On Fri, 09 Dec 2005 12:38:14 +1000, Tamyka Bell <t.bell@uq.edu.au>
> wrote:
>
>
>>My point was to look ahead. Don't look at the car in front. Look as far
>>ahead as you can. Change lanes early while you are still moving at
>>70km/h. That's not difficult. I manage that all the time. I even managed
>>that when driving in Sydney. My driving instructor taught me to look
>>ahead. It should be part of basic driver education.
>
>
> So two lanes of traffic change into one lane, with no traffic
> disruption?
> Magic!
>
> Or is it just you change lanes and everybody else gets stuck behind
> the cyclist.
>
>
>>Also, while you are required to give way when changing lanes, if there
>>is insufficient space to change lanes between two vehicles, then those
>>two vehicles are too close.
>
>
> Rubbish. The safe distance between cars is equal to the emergency
> stopping distance. To change lanes when you have to give way there has
> to be enough room for you to move across and then accelate without
> obstructing the other car. Many more times that safe stopping
> distance. Unless you just pull out illegally and force them to break
> hard (which a lot of drivers do).

Sounds like you are advocating using up their safe stopping distance.
>
> There is no way you can change lanes into a continous stream of
> traffic driving much faster than you unless there is large gap in the
> traffic, much larger than safe stopping distance.
Its why many of us have big bikes but nevermind.
>
>

"Theo Bekkers" <tbekkers@bekkers.com.au> wrote in message
news:4398f650$1@news.bekkers.com.au...
> Tamyka Bell wrote:
>
>> The reason why traffic stop-starts is largely because people don't
>> leave enough following distance. If you leave a large enough gap, you
>> can react more gradually, and therefore you don't change speeds as
>> much. This should be bloody obvious but apparently 80% of peak hour
>> drivers don't understand it.
>
> They really have little control over the traffic density. A bunch of cars
> is travelling at the correct 2 sec gap, cars merge in from the left, next
> entry point more cars merge in from the left, and again at every entry
> point. Eventually the gaps decrease to nothing and everybody stops.
>
> Some years ago they increased the freeway speed limit in Perth from 80 to
> 100 on the reasoning that they would be able to move more cars on the
> freeway. Whilst the end to end time spent on the freeway will decrease
> with a higher speed limit, the amount of cars on the freeway remains the
> same. With a 2 sec gap you can move 30 cars per minute per lane at 100, at
> 80, at 60, and at 20 km/h. To move more vehicles you need more lanes.
>
> Theo

Actually, once you drop below about 30kph (if I recall correctly - I'm
willing to be corrected on the actual speed) the safe following distance in
terms of time drops markedly. At 20kph, 1-1½ seconds is ample beacause you
can stop much more quickly. Ergo, you can fit through more vehicles per
hour. This may be why trip times have been shown to improve with very dense
traffic when speed limits are heavily reduced.

dewatf wrote:
<snip>
> Even if you are moving at the same speed you can then change into the
> safe stopping distance, but that then forces the car behind to slow
> down to re-establish safe stopping distance, which flows back up the
> road, and on a road that is at full capacity causes traffic to grind
> to a halt. Obviously you have never driven on the F3 in peak hour
> where that happens all the time.
>
> dewatf.

I choose to ride rather than contribute to the "full capacity."

Resound wrote:
> "Theo Bekkers" wrote

>> With a 2 sec gap you can move 30 cars per
>> minute per lane at 100, at 80, at 60, and at 20 km/h. To move more
>> vehicles you need more lanes.

> Actually, once you drop below about 30kph (if I recall correctly - I'm
> willing to be corrected on the actual speed) the safe following
> distance in terms of time drops markedly. At 20kph, 1-1½ seconds is
> ample beacause you can stop much more quickly. Ergo, you can fit
> through more vehicles per hour. This may be why trip times have been
> shown to improve with very dense traffic when speed limits are
> heavily reduced.

Errr, right. With a 2 second gap between cars at 100 km/h, and allowing for
a 5 metre car length, each car will use 60.5 metres of roadway which is 2.18
seconds at that speed. At 60 km/h, 38.3 metres and 2.31 seconds. At 20km/h,
16 metres and 2.9 seconds. If we reduce the gap at 20km/h to just one
second, 10.5 metres and 1.9 seconds. one and a half seconds would give you
13.3 metres and 2.4 seconds. Yes, at 20km/h and reducing the gap to one
second, you can fit 15% more cars on the road than at 100 km/h. Explain to
me again how that makes your trip faster?

Theo

"Theo Bekkers" <tbekkers@bekkers.com.au> wrote in message
news:439d0453$1@news.bekkers.com.au...
> Resound wrote:
>> "Theo Bekkers" wrote
>
>>> With a 2 sec gap you can move 30 cars per
>>> minute per lane at 100, at 80, at 60, and at 20 km/h. To move more
>>> vehicles you need more lanes.
>
>> Actually, once you drop below about 30kph (if I recall correctly - I'm
>> willing to be corrected on the actual speed) the safe following
>> distance in terms of time drops markedly. At 20kph, 1-1½ seconds is
>> ample beacause you can stop much more quickly. Ergo, you can fit
>> through more vehicles per hour. This may be why trip times have been
>> shown to improve with very dense traffic when speed limits are
>> heavily reduced.
>
> Errr, right. With a 2 second gap between cars at 100 km/h, and allowing
> for a 5 metre car length, each car will use 60.5 metres of roadway which
> is 2.18 seconds at that speed. At 60 km/h, 38.3 metres and 2.31 seconds.
> At 20km/h, 16 metres and 2.9 seconds. If we reduce the gap at 20km/h to
> just one second, 10.5 metres and 1.9 seconds. one and a half seconds would
> give you 13.3 metres and 2.4 seconds. Yes, at 20km/h and reducing the gap
> to one second, you can fit 15% more cars on the road than at 100 km/h.
> Explain to me again how that makes your trip faster?
>
> Theo
>

This was in dense traffic that was stop/start. The problem is that when it
moves, it does so at 50-60 kph, therefore gaps are longer therefore fewer
cars per lane per minute, therefore it all clogs up faster. If you spend 5%
of your time @ 60kph, 5% @ 5kph and 90% stopped and staring at the
stationary car in front of you, you don't get from point a to point b as
fast as someone who spends even 60% of their time @ 30kph. This is why I'm
faster through the CBD on my bike than cars are even though I average well
under 30kph.

Resound wrote:

> This was in dense traffic that was stop/start. The problem is that
> when it moves, it does so at 50-60 kph, therefore gaps are longer
> therefore fewer cars per lane per minute, therefore it all clogs up
> faster. If you spend 5% of your time @ 60kph, 5% @ 5kph and 90%
> stopped and staring at the stationary car in front of you, you don't
> get from point a to point b as fast as someone who spends even 60% of
> their time @ 30kph. This is why I'm faster through the CBD on my bike
> than cars are even though I average well under 30kph.

Yes. Moving at 30km/h is quicker than being stationary.

Theo