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OT: red light jumping

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UK and Europe
Published
13 December 2004
Last activity
24 December 2004
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Colin Blackburn
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  1. In the many threads on this I have probably more than once mentioned the
    lights near my office as a prime example of a set of lights where
    motorists routinely go through red lights. Well, this morning as I
    approached the lights, walking, they were just changing. As the red
    light came on the lead car came to a halt so quickly it skidded several
    yards over the stop line. The sound was quite dramatic. Interestingly
    there was a police car parked on the opposite corner attending a broken
    down car.

    Colin

  2. Colin Blackburn said:

    As the red light came on the lead car came to a halt so quickly it
    skidded several yards over the stop line. The sound was quite
    dramatic. Interestingly there was a police car parked on the
    opposite corner attending a broken down car.

    The police of course were probably much more attracted by the
    "emergency" stop than they would have been by routine red light
    running. The cager's poor decision making and lack of observation are
    more worrying to me than his simple disregard for the lights.
    --
    Dave...

  3. dkahn400 said:


    The police of course were probably much more attracted by the
    "emergency" stop than they would have been by routine red light
    running. The cager's poor decision making and lack of observation are
    more worrying to me than his simple disregard for the lights.

    There is a problem that the amber phase of many lights is shorter than
    the reaction and stopping time so that depending on where you are when
    the light changes to amber and how fast you were going at the time, this
    can be the consequence if you try to stop

    Tony

  4. Tony Raven said:
    dkahn400 said:


    The police of course were probably much more attracted by the
    "emergency" stop than they would have been by routine red light
    running. The cager's poor decision making and lack of observation are
    more worrying to me than his simple disregard for the lights.

    There is a problem that the amber phase of many lights is shorter than
    the reaction and stopping time so that depending on where you are when
    the light changes to amber and how fast you were going at the time, this
    can be the consequence if you try to stop

    Are you really suggesting that somebody driving at a legal speed towards
    a green traffic light can find that the light changes to amber *and
    red*, before the vehicle passes the stop line, so quickly that the
    vehicle cannot be brought to a controlled stop before the stop line?

    I'd be interested to know of some examples.

    --
    Joe * If I cannot be free I'll be cheap

  5. The police officer did nothing of course 😠

  6. JLB said:


    Are you really suggesting that somebody driving at a legal speed towards
    a green traffic light can find that the light changes to amber *and
    red*, before the vehicle passes the stop line, so quickly that the
    vehicle cannot be brought to a controlled stop before the stop line?

    I'd be interested to know of some examples.

    I am indeed. Its known as the dilemma zone - you are too close to stop
    at the line but too far away to cross the line before the light goes red
    An example of TRL research is:

    Quoted message said:

    UG131: REAPPRAISAL OF STOPPING AMBER

    TRL reviewed the operation of traffic signals on high-speed roads, where the 3-second duration of the amber signal has caused concern. Some drivers may find it difficult to know whether or when to brake sharply and stop, or to risk being recorded by cameras for crossing traffic lights at red. Simulator trials at TRL by a sample of 40 motorists recorded and compared reactions of drivers to the use of an advanced warning of signals changing from green to amber, with the normal arrangement where there is the standard sequence. The simulations included a variety of situations whereby the presence of other vehicles would be influencing the driver's decisions.

    The research conclusion was that i) advance warning of a change to amber should not be used, ii) the current value of 3 seconds stopping amber should be retained for traffic signals, even on high speed roads, the all red period being adjusted to provide a safe change between opposing flows and iii) on red light cameras a minimum activation time, following the amber, should be commensurate with the safe operation of the signals.

    Consequently, no change to the policy of 3-seconds amber is recommended. The implications for the setting of red-light cameras on high-speed roads are being considered.

    For these purposes "high speed" means over 35mph and the clear
    recommendation is 3 seconds is too short for stopping reliably within
    the amber so accept that cars will cross at red and set the trigger
    delay on the red light cameras so as to not catch them and run a longer
    dual red phase so they won't hit crossing traffic.

    Tony

  7. Tony Raven said:
    JLB said:


    Are you really suggesting that somebody driving at a legal speed
    towards a green traffic light can find that the light changes to amber
    *and red*, before the vehicle passes the stop line, so quickly that
    the vehicle cannot be brought to a controlled stop before the stop line?

    I'd be interested to know of some examples.

    I am indeed. Its known as the dilemma zone - you are too close to stop
    at the line but too far away to cross the line before the light goes red
    An example of TRL research is:

    Quoted message said:

    UG131: REAPPRAISAL OF STOPPING AMBER

    TRL reviewed the operation of traffic signals on high-speed roads,
    where the 3-second duration of the amber signal has caused concern.
    Some drivers may find it difficult to know whether or when to brake
    sharply and stop, or to risk being recorded by cameras for crossing
    traffic lights at red. Simulator trials at TRL by a sample of 40
    motorists recorded and compared reactions of drivers to the use of an
    advanced warning of signals changing from green to amber, with the
    normal arrangement where there is the standard sequence. The
    simulations included a variety of situations whereby the presence of
    other vehicles would be influencing the driver's decisions.

    The research conclusion was that i) advance warning of a change to
    amber should not be used, ii) the current value of 3 seconds stopping
    amber should be retained for traffic signals, even on high speed
    roads, the all red period being adjusted to provide a safe change
    between opposing flows and iii) on red light cameras a minimum
    activation time, following the amber, should be commensurate with the
    safe operation of the signals.

    Consequently, no change to the policy of 3-seconds amber is
    recommended. The implications for the setting of red-light cameras on
    high-speed roads are being considered.

    For these purposes "high speed" means over 35mph and the clear
    recommendation is 3 seconds is too short for stopping reliably within
    the amber so accept that cars will cross at red and set the trigger
    delay on the red light cameras so as to not catch them and run a longer
    dual red phase so they won't hit crossing traffic.

    Thanks! I do find that interesting. To paraphrase the suggested policy,
    going through a red light on such junctions will not bring about
    enforcement action until after the red has been on for some period of
    time. It looks as though people will not be told what that period of
    time is. This is not exactly ideal from several points of view, though I
    can see why some other options might be thought even worse.

    The best answer would be a blanket national speed limit of 30 mph.
    Except for cyclists.
    --
    Joe * If I cannot be free I'll be cheap

  8. JLB said:


    Thanks! I do find that interesting. To paraphrase the suggested policy,
    going through a red light on such junctions will not bring about
    enforcement action until after the red has been on for some period of
    time. It looks as though people will not be told what that period of
    time is. This is not exactly ideal from several points of view, though I
    can see why some other options might be thought even worse.

    The best answer would be a blanket national speed limit of 30 mph.
    Except for cyclists.

    Even that wouldn't work. A three second delay works if you are staring
    at the light waiting for it to change. If you have just checked your
    mirrors or you are keeping an eye on a pedestrian waiting to cross the
    road, you can easily add another second before the light changing will
    register. The TRL problem is they did it in lab conditions not in real
    life busy road environment lots of other things to be dealing with
    environment. In those environment delay times before people start
    braking can be a couple of seconds or more rather than the normal
    3-600ms reaction time.

    Tony

  9. Tony Raven said:
    JLB said:


    Thanks! I do find that interesting. To paraphrase the suggested
    policy, going through a red light on such junctions will not bring
    about enforcement action until after the red has been on for some
    period of time. It looks as though people will not be told what that
    period of time is. This is not exactly ideal from several points of
    view, though I can see why some other options might be thought even
    worse.

    The best answer would be a blanket national speed limit of 30 mph.
    Except for cyclists.

    Even that wouldn't work.

    I did not say, nor did I think, that it would work all the time for
    everyone, solve all problems or produce peace, happiness and eternal
    bliss on earth. I was only suggesting that it would be the best of the
    practical options available. It would work for most people most of the
    time (except for those who want to exceed 30 mph, who might not be too
    happy, but, hey, stuff them).

    A three second delay works if you are staring

    Quoted message said:

    at the light waiting for it to change. If you have just checked your
    mirrors or you are keeping an eye on a pedestrian waiting to cross the
    road, you can easily add another second before the light changing will
    register. The TRL problem is they did it in lab conditions not in real
    life busy road environment lots of other things to be dealing with
    environment. In those environment delay times before people start
    braking can be a couple of seconds or more rather than the normal
    3-600ms reaction time.

    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. However, any problems this
    causes at 30 mph will be proportionately worse at higher speeds; and the
    minimum braking distance increases more than proportionately.

    --
    Joe * If I cannot be free I'll be cheap

  10. Maybe I am missing something here but the Police don´t give a [censored] about red lights and I NEVER expect anyone to obey red lights. I am a cyclist and usually better off and safer ignoring the red lights sometimes. I behave though. I just don´t hang up my life on stats and lab tests.

    quote='JLB'Tony Raven said:
    JLB said:


    Thanks! I do find that interesting. To paraphrase the suggested
    policy, going through a red light on such junctions will not bring
    about enforcement action until after the red has been on for some
    period of time. It looks as though people will not be told what that
    period of time is. This is not exactly ideal from several points of
    view, though I can see why some other options might be thought even
    worse.

    The best answer would be a blanket national speed limit of 30 mph.
    Except for cyclists.

    Even that wouldn't work.

    I did not say, nor did I think, that it would work all the time for
    everyone, solve all problems or produce peace, happiness and eternal
    bliss on earth. I was only suggesting that it would be the best of the
    practical options available. It would work for most people most of the
    time (except for those who want to exceed 30 mph, who might not be too
    happy, but, hey, stuff them).

    A three second delay works if you are staring

    Quoted message said:

    at the light waiting for it to change. If you have just checked your
    mirrors or you are keeping an eye on a pedestrian waiting to cross the
    road, you can easily add another second before the light changing will
    register. The TRL problem is they did it in lab conditions not in real
    life busy road environment lots of other things to be dealing with
    environment. In those environment delay times before people start
    braking can be a couple of seconds or more rather than the normal
    3-600ms reaction time.

    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. However, any problems this
    causes at 30 mph will be proportionately worse at higher speeds; and the
    minimum braking distance increases more than proportionately.

    --
    Joe * If I cannot be free I'll be cheap[/QUOTE]

  11. Tony Raven said:
    Quoted message said:

    There is a problem that the amber phase of many lights is shorter than
    the reaction and stopping time so that depending on where you are when
    the light changes to amber and how fast you were going at the time, this
    can be the consequence if you try to stop

    JLB said:

    Are you really suggesting that somebody driving at a legal speed towards
    a green traffic light can find that the light changes to amber *and
    red*, before the vehicle passes the stop line, so quickly that the
    vehicle cannot be brought to a controlled stop before the stop line?

    I'd be interested to know of some examples.

    I've had this happen on my bike. It was a couple of years ago on
    Warmley High Street. I would have been riding at about 20-25mph, when a
    ped pressed the button at a pelican crossing. The light changed
    instantly to amber. I was still far enough from the crossing that I
    *could* have stopped, if I'd slammed everything on, but I decided it was
    safer not to try (AFAIR the road was wet, which would have influenced my
    decision). Then the light changed to red before I actually reached the
    crossing - I had no choice but to carry on through the red light.

    Most embarrassing.

    --
    Danny Colyer (the UK company has been laughed out of my reply address)
    <URL:http://www.speedy5.freeserve.co.uk/danny/>
    "He who dares not offend cannot be honest." - Thomas Paine

  12. JLB said:


    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. Meanwhile they have travelled 14-27m
    without looking forward except for peripheral vision.

    Tony

  13. MadDog62 said:

    Maybe I am missing something here but the Police don´t give a [censored] about
    red lights and I NEVER expect anyone to obey red lights. I am a cyclist
    and usually better off and safer ignoring the red lights sometimes. I
    behave though. I just don´t hang up my life on stats and lab tests.

    Possibly you are missing something here, since the thread began with a
    description of a car going through a red light despite doing its best to
    stop; that led to a discussion of the consequences of the standard
    three-second period of amber, and how it has been shown that for
    junctions where drivers approach at speeds in excess of 35 mph many
    drivers will not be able to halt in time for the change to red, leading
    to a recommendation that at such junctions the other lights stay red for
    long enough to let the stragglers through before the next group of
    drivers enter the junction. Hence it was pretty much off topic, because
    it was about vehicle traffic and had little to say about cyclists or
    cycling.

    Just a small suggestion: on Usenet, including urc, it's customary to
    place the new post below whatever is being quoted, rather than
    top-posting. It helps readers to get the context before reading the new
    contribution.

    --
    Joe * If I cannot be free I'll be cheap

  14. On Mon, 13 Dec 2004 16:09:31 +0000,

    JLB said:


    Are you really suggesting that somebody driving at a legal speed towards
    a green traffic light can find that the light changes to amber *and
    red*, before the vehicle passes the stop line, so quickly that the
    vehicle cannot be brought to a controlled stop before the stop line?

    I'd be interested to know of some examples.


    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.

    But at that same 30mph you will do 132 feet if you don't brake at all
    so, in theory, at 30mph you shouldn't have a problem. More than 100 feet
    away and you can stop easily, less than 100 feet and you can cross the
    junction easily. (I'm ignoring thinking times here)

    According to the highway code it takes 4.8 seconds to stop from 70mph.

    And in three seconds you will travel 300 feet which is just about the
    highway code stopping distance.

    But you have to make a split second decision to emergency stop or carry
    on. Further away isn't usually a problem - you will stop easily, it's
    when it starts getting a bit closer. Say you are 200 feet away when the
    lights change - if you don't brake it won't be a problem. If you do
    brake you won't be able to stop before the line but there will be time
    for the lights to go to red before you get to the line.

    Add on the 0.7 seconds of reaction time (you are expecting the lights to
    change so going for the lower limits of reaction is reasonable) and at
    70mph distances from 306 to 315 feet are lose-lose - you can't stop in
    time but you can't get across before the lights turn to red.

    There are a few dual carriageways with lights - it's scary when you
    start to brake from 70mph, realize you won't stop, back on the throttle
    at about 50mph and then see the light go to red a long time before you
    actually get to them.

    Now on any fast road when approaching traffic lights I always have a
    "point of no return" in my mind after which I ignore the lights
    (other than being ready for someone coming the other way to jump their
    lights but that can happen regardless of what my lights are saying)

    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/

  15. Tim Woodall said:


    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

    Tony

  16. On Mon, 13 Dec 2004 22:34:48 +0000, Tony Raven <[email hidden]>

    Quoted message said:

    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

  17. Provence1971 said:

    The police officer did nothing of course 😠


    To be fair he was actually dealing with another incident at the time.

    Colin

  18. Just zis Guy said:

    On Mon, 13 Dec 2004 22:34:48 +0000, Tony Raven <[email hidden]>

    Quoted message said:

    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

  19. On Mon, 13 Dec 2004 22:34:48 +0000, Tony Raven <[email hidden]>

    Quoted message said:
    JLB said:


    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.

  20. On Tue, 14 Dec 2004 07:44:43 +0000, Tony Raven <[email hidden]>

    Quoted message said:
    Tim Woodall said:


    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 !!

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