OT: red light jumping

Just zis Guy, you know?

On Mon, 13 Dec 2004 22:34:48 +0000, Tony Raven <junk@raven-family.com>
wrote:

>a good driver should be regularly checking his mirrors and that
>takes 0.5 - 1s per time and I don't think anyone would suggest a
>competent driver should not do so. Meanwhile they have travelled 14-27m
>without looking forward except for peripheral vision.

Surely the inevitable result here is that a child will run out and be
mown down? Or is that only when they look at their speedo?

Incidentally, it is good practice to slow down and cover the brake
when approaching light-controlled junctions. Or so my driving
instructor told me.

Guy
--
May contain traces of irony. Contents liable to settle after posting.
http://www.chapmancentral.co.uk

88% of helmet statistics are made up, 65% of them at CHS, Puget Sound

Colin Blackburn

Provence1971 wrote:
> The police officer did nothing of course
>
To be fair he was actually dealing with another incident at the time.

Colin

Velvet

Just zis Guy, you know? wrote:
> On Mon, 13 Dec 2004 22:34:48 +0000, Tony Raven <junk@raven-family.com>
> wrote:
>
>
>>a good driver should be regularly checking his mirrors and that
>>takes 0.5 - 1s per time and I don't think anyone would suggest a
>>competent driver should not do so. Meanwhile they have travelled 14-27m
>>without looking forward except for peripheral vision.
>
>
> Surely the inevitable result here is that a child will run out and be
> mown down? Or is that only when they look at their speedo?
>
> Incidentally, it is good practice to slow down and cover the brake
> when approaching light-controlled junctions. Or so my driving
> instructor told me.
>
> Guy

Indeed. There's a set of lights on a dual carriageway near me. The
limit as you approach the lights (they are only applicable to one
direction) is 70. The lights themselves change fast, and seem to be set
up such that the both-red period can't be more than a second, if that.
I suspect in actual fact the side-junction is leery of pulling out till
they can see the cars on the dual have actually stopped, in practice, so
quite possible (as with other light-controlled junctions around here)
that there is no all-red period to them.

Anyway, the upshot is that there are those who will not slow approaching
the lights and will continue through on red, because they can't stop in
the time it takes to react/brake when they go amber (not very long spent
on amber, either, it has to be said). This isn't a problem, because if
they *genuinely* are too close, then they'll be through before the side
road moves off - because it's well known. Others will slow approaching
it, or are slowed by those in front filtering off to the left at the
junction - the majority of those will stop in time, due to having
already lifted off the throttle, if not already covering the brake.

Having driven through this junction many many *many* times, I've had
ample opportunity to try different tactics. What I've perceived whilst
doing this is that either all my cars stop on a sixpence (unlikely) or
it's a case that people don't know how fast their cars *could* stop if
they really wanted them to (and if you've been using your mirror, you
know if you'll end up with a following-too-closer in your boot if you
throw the anchor out). And I don't class the stops I do as emergency
ones - I could brake a fair bit sharper if it really was a 'stop or kill
something' situation. Many of my decisions to continue through are due
to it being a close call - being able to stop in time but being followed
too close. Often I'll stop, and a car or two in the lane next to me
will go flying through. If I approach at 70, though, without having
lifted off and the speed dropping, then I know I don't have enough time
to stop even though I know the instant the lights change I'll see them
(if you're coming up this fast to lights, you have already looked in
your mirrors and are looking at the lights/side junction!).

Not all 70mph trafficlight junctions have this characteristic of
approaching at 70 - in this instance it's the only one on the length of
the dual carriageway, the lanes merge to 1 shortly after as you climb up
a hill, and who knows what's about to turn out of the side junction and
then crawl up said hill at snails pace.

That said, there's a lot of lazyness around, and I think it's lazyness
and not knowing how fast you can stop your car that contributes to the
majority of red-light running on this junction, and I'm willing to bet
on others, too. Red light running is so common these days that I'm wary
of moving off till I can see the other traffic is slowing enough that
they'll stop, and not just wavering in indecision. This makes the
actual throughput of junctions even lower than normal, of course, and
increases congestion ;-)

--


Velvet

Jack Ouzzi

On Mon, 13 Dec 2004 22:34:48 +0000, Tony Raven <junk@raven-family.com>
wrote:

>JLB wrote:
>>
>> At 30 mph a driver who is distracted for two seconds has travelled about
>> 27 metres (apologies for the inconsistent units) without paying
>> attention to relevant matters. I don't suppose anyone has credible
>> figures for how frequently drivers do this.
>
>Well a good driver should be regularly checking his mirrors and that
>takes 0.5 - 1s per time and I don't think anyone would suggest a
>competent driver should not do so.

AND also ANTICIPATE that the lights may change to red, and be prepared
to stop in time in that case.

Jack Ouzzi

On Tue, 14 Dec 2004 07:44:43 +0000, Tony Raven <junk@raven-family.com>
wrote:

>Tim Woodall wrote:
>>
>> I think the amber phase of most lights is of the order of 3 seconds.
>>
>> Allow a respectable 0.5g braking and you get a speed a little over
>> 30mph that you can stop from.
>>
>
>You've forgotten to allow for reaction times before you start braking.
>You need at least 1.25s for that.
>http://www.visualexpert.com/Resources/reactiontime.html
>
>

OR 8.3 seconds if you have had 6 pints, 4 whiskies and a joint :-|

Believe me they are out there !!

Tony Raven

Just zis Guy, you know? wrote:
>
> Incidentally, it is good practice to slow down and cover the brake
> when approaching light-controlled junctions. Or so my driving
> instructor told me.
>
> Guy

The slowing down will help but covering the brake only saves about 200ms.

Tony

Just zis Guy, you know?

On Tue, 14 Dec 2004 14:47:44 +0000, Tony Raven <junk@raven-family.com>
wrote in message <328d5oF3iumciU3@individual.net>:

>The slowing down will help but covering the brake only saves about 200ms.

The reason for covering the brake is to ensure that the default action
becomes braking rather than accelerating, should something unexpected
happen. My driving instructor was quite keen on that one.

My driving instructor was John Milne, now MBE and Head of Training at
the Approved Driving Instructors National Joint Council, an old friend
of the family whose late wife used to give me second helpings of pud
in the college canteen. Back then he was not an MBE, although the
Pater informs me he was one of five people employed by the DoT as was
to assess driving instructor examiners. Another was Fred Williams,
who taught my sister. Dad was active in road safety in St Albans in
nineteen hundred and frozen to death, so he picked us the best
instructors he could find. And then took me out to practice in a car
which, as it turned out, had no brakes, which meant some fast
learning...

Guy
--
"then came ye chavves, theyre cartes girded wyth candels
blue, and theyre beastes wyth straynge horn-lyke thyngs
onn theyre arses that theyre fartes be herde from myles
around." Chaucer, the Sheppey Tales

Tim Woodall

On Tue, 14 Dec 2004 07:44:43 +0000,
Tony Raven <junk@raven-family.com> wrote:
> Tim Woodall wrote:
>>
>> I think the amber phase of most lights is of the order of 3 seconds.
>>
>> Allow a respectable 0.5g braking and you get a speed a little over
>> 30mph that you can stop from.
>>
>
> You've forgotten to allow for reaction times before you start braking.
> You need at least 1.25s for that.
> http://www.visualexpert.com/Resources/reactiontime.html
>
You snipped:
>> (I'm ignoring thinking times here)

So no i didn't forget them.

And in this instance 1.25 seconds is long. I'm assuming you are
approaching the green lights and have seen them and are anticipating
that they might change.

I would expect perception time to approach zero - you are waiting for
the light to change. The physical motion of the leg is still going to
take around 0.2 seconds.

Olympic sprinters have _left_ the blocks within 0.5 seconds of the
gun going off.

http://condellpark.com/kd/reactiontime.htm

For about 120 years, the accepted figures for mean simple reaction times
for college-age individuals have been about 190 ms (0.19 sec) for light
stimuli and about 160 ms for sound stimuli (Galton, 1899; Fieandt et
al., 1956; Welford, 1980; Brebner and Welford, 1980).

Elite 100 m sprinters are way above the mean in at least running
performance, but their mean reaction times are not much better than the
average. For example, in the July 12 2003 Rome Golden League A & B
Series 100m sprints, reaction times averaged 153 mS (standard deviation
28 mS) - the minimum was 110 mS, max was 242 mS; there was virtually no
correlation between running time and reaction time (r^2=0.02).


Tim.


--
God said, "div D = rho, div B = 0, curl E = - @B/@t, curl H = J + @D/@t,"
and there was light.

http://tjw.hn.org/ http://www.locofungus.btinternet.co.uk/

Tony Raven

Tim Woodall wrote:

>>http://www.visualexpert.com/Resources/reactiontime.html

>
> And in this instance 1.25 seconds is long. I'm assuming you are
> approaching the green lights and have seen them and are anticipating
> that they might change.
>
> I would expect perception time to approach zero - you are waiting for
> the light to change. The physical motion of the leg is still going to
> take around 0.2 seconds.
>

Try reading the link I posted. 1.25s is the typical reaction time to
traffic lights. Its not just reacting. There is also the time to notice
the change and then the thinking time to assess whether you should carry
on and cross on amber or brake and stop. So add another 3s to slow at
0.5g from 30mph. That makes it crossing the line 1.25s after the lights
have gone red if they change when you are at the worst place.

Tony

Jack Ouzzi

On Wed, 15 Dec 2004 00:17:28 +0000, Tony Raven <junk@raven-family.com>
wrote:

>Tim Woodall wrote:
>
>>>http://www.visualexpert.com/Resources/reactiontime.html
>
>>
>> And in this instance 1.25 seconds is long. I'm assuming you are
>> approaching the green lights and have seen them and are anticipating
>> that they might change.
>>
>> I would expect perception time to approach zero - you are waiting for
>> the light to change. The physical motion of the leg is still going to
>> take around 0.2 seconds.
>>
>
>Try reading the link I posted. 1.25s is the typical reaction time to
>traffic lights. Its not just reacting. There is also the time to notice
>the change and then the thinking time to assess whether you should carry
>on and cross on amber or brake and stop. So add another 3s to slow at
>0.5g from 30mph. That makes it crossing the line 1.25s after the lights
>have gone red if they change when you are at the worst place.
>
>Tony

Jack Ouzzi

On Wed, 15 Dec 2004 08:44:20 +0000, Jack Ouzzi
<nospam@nowayhose.co.au> wrote:

>On Wed, 15 Dec 2004 00:17:28 +0000, Tony Raven <junk@raven-family.com>
>wrote:
>
>>Tim Woodall wrote:
>>
>>>>http://www.visualexpert.com/Resources/reactiontime.html
>>
>>>
>>> And in this instance 1.25 seconds is long. I'm assuming you are
>>> approaching the green lights and have seen them and are anticipating
>>> that they might change.
>>>
>>> I would expect perception time to approach zero - you are waiting for
>>> the light to change. The physical motion of the leg is still going to
>>> take around 0.2 seconds.
>>>
>>
>>Try reading the link I posted. 1.25s is the typical reaction time to
>>traffic lights. Its not just reacting. There is also the time to notice
>>the change and then the thinking time to assess whether you should carry
>>on and cross on amber or brake and stop. So add another 3s to slow at
>>0.5g from 30mph. That makes it crossing the line 1.25s after the lights
>>have gone red if they change when you are at the worst place.
>>
>>Tony

Whoops, sorry got a new mouse and the buttons are a bit more
sensitive

Trevor Barton

On Tue, 14 Dec 2004 19:27:58 +0000, Just zis Guy, you know? wrote:
> My driving instructor was John Milne, now MBE and Head of Training at
> the Approved Driving Instructors National Joint Council, an old friend
> of the family whose late wife used to give me second helpings of pud
> in the college canteen. Back then he was not an MBE, although the
> Pater informs me he was one of five people employed by the DoT as was
> to assess driving instructor examiners. Another was Fred Williams,
> who taught my sister.

> Dad was active in road safety in St Albans in
> nineteen hundred and frozen to death,

Eh?

> so he picked us the best
> instructors he could find. And then took me out to practice in a car
> which, as it turned out, had no brakes, which meant some fast
> learning...
>
> Guy
> --
> "then came ye chavves, theyre cartes girded wyth candels
> blue, and theyre beastes wyth straynge horn-lyke thyngs
> onn theyre arses that theyre fartes be herde from myles
> around." Chaucer, the Sheppey Tales


--
Trevor Barton

David Martin

On 15/12/04 9:00 am, in article slrncrvv8t.ae1.tmb@sheep.isotek.co.uk,
"Trevor Barton" <tmb@Xisotek.co.uk> wrote:

>
>> Dad was active in road safety in St Albans in
>> nineteen hundred and frozen to death,
>
> Eh?

A long time ago.

...d

Peter B

"Just zis Guy, you know?" <norfolk.inspam@dev.null> wrote in message
news:elbtr09rjuo2be388vflb8idua55ir9a38@4ax.com...
> Incidentally, it is good practice to slow down and cover the brake
> when approaching light-controlled junctions. Or so my driving
> instructor told me.

Wrong!
Best practice is to cover the accelerator so that if the lights turn to
amber one can react immediately. Or so Arriva driving instructors seem to
tell their trainees.

Pete